 
### Epitome for Eleanor: A Short History of the Known Universe

### I

### The Big Bang to the Bronze Age

Smashwords Edition  
Copyright 2014 Justin Cahill

Smashwords Edition, License Notes  
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Please direct all inquiries to Justin Cahill at  
PO Box 108, Lindfield, 2070  
New South Wales, Australia  
or email to mailto:jpjc@ozemail.com.au

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**Epitome** (from Greek: πιτέμνειν, _epitemnein_ , meaning to cut short, to abridge): A summary; a condensed, distilled account; an instance that represents a larger reality.

Respectfully dedicated to

the memories of Carl Sagan, Stephen Gould, Jacob Bronowski, Glyn Daniel and

Sir Kenneth Clark and to Sir David Attenborough, Adrian Desmond, James Moore,

Baron Renfrew of Kaimsthorn and Michael Wood.

" _[W]e are dwarfs astride the shoulders of giants. We master their wisdom and move beyond it. Due to their wisdom we grow wise and are able to say all that we say, but not because we are greater than they_."

– Isaiah di Trani, _She'elot u-Teshuvot ha-Rif_ , 301-303.

" _I like non-fiction ! There's so much to know about this World. I think you read something [and] somebody just invented it ? Waste of time !_ "

\- Barbara's father in _Sideways_ , Twentieth Century Film Corporation, 2004.

Cover illustration: Painting of the fresco of a Minoan lady known as 'La Parisienne', found at the Palace of Knossos in 1901 and dated 1400 to 1350 BC. This painting, made by Emile Gilliéron père in 1908, is reproduced by kind permission of The Metropolitan Museum of Art, New York (www.metmuseum.org). The original fresco is in the Archaeological Museum at Heraklion in Crete.

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Contents

Welcome !

I. Knowledge

II. The Universe

III. Earth

IV. Life

V. Us

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**Welcome !**

Dear Eleanor,

Welcome ! It seems like only yesterday that we brought you home from the hospital – but now you are almost three. As you already know, there is so much to find out about everything. But why care about all these things ? Surely it's more fun to watch _Hoopla Doopla_ or play outside ?

The answer is simple: knowledge is strength. You'll need many skills in life. They include 'insight', which is knowledge of yourself, and 'empathy', which is an understanding of others. They are important for your development as both an individual and a citizen. This is because they help you work out ways to treat others the way you'd like them to treat you and to give everyone their due.

But above all you will need to develop good judgment. To do this, you must be able to work out if something is right or wrong, good or bad, or somewhere in between. To do this, it's not enough just to know a lot of things. You must be able to work out their strengths and weaknesses. Often, you will have to persuade other people that you are right. There are three skills you must learn to achieve this: how to collect, assess and present information - especially information about things that happened in the past.

We can learn a lot from the past. It gives us many examples of good and bad things and people, and a few that were somewhere in between. We are here only once, and for such a short time. Who wants to make the same mistake twice ?

As you can see, while we know a lot about ourselves and the past, there is a lot we don't know. You are already starting to ask us some difficult questions. Just the other day you asked Mummy " _where was Baby Tom before he was born ?"_ No-one knows. What is Baby Tom ? We can see he has a body, a happy smile and that he likes to chat. But are his body and his personality the same thing, or are they separate things ? Has his personality always existed, only waiting to be born ?

Maybe you will work some of these things out. After all, your mind is not just a bottle to be filled with facts and figures, but a fire to be lit. So I have put together this little epitome to get you started.

It is divided into four parts. Parts I and II are about things that have happened since time began. After that, in part III, we look at the ways we have developed to understand the universe and ourselves. Then, in part IV, we look at how our cultures and societies are structured, their achievements and our future.

This little book is only meant as a general guide, not as a textbook or code. Never hesitate to ask us, or anyone else, any questions you might have. We will not always have the answers, but we can often point you in the right direction. Over time, you will find your own way and your own answers.

Your loving Father,

Lindfield, 2014

**I. Knowledge**

i

How do we know what we know ? There are three types of knowledge: experience, reason and faith. Experience is the knowledge we gain through our senses. It is the things we see, hear, smell, taste or touch.

Reason is the knowledge we gain by deducing or inducing information from what we sense. We deduce things when we reason from general things to individuals. So, for example, if we see that all cats have whiskers, we can deduce that Julia and Lily will have whiskers. We induce things when we reason from individuals to things in general. So as cats have tails, we can induce that all cats have tails. Julia and Lily are very proud of their tails.

But this doesn't always work. There is a type of cat from the Island of Manx that has no tail. So sometimes we need to remember not everything falls into neat and tidy categories. We call these things 'grey areas'.

Finally, there is faith. This is knowledge that you accept without having either sensed or reasoned it. There are many things we experience that we cannot see. Things such as kindness and love cannot be seen. We can see people give these things, but not the things themselves. So how do we know they really exist ? Many people believe these things come from the gods; all-power beings we cannot see who know all and see all.

There are many people who say " _I'll believe it when I see it !_ " I suppose seeing something is the best way of knowing about it. But, in reality, we all use a combination of experience, reason and faith to work our way through life. So sometimes it can be difficult to work out who is right or wrong. Life is full of grey areas.

ii

The people who study grey areas fall into several groups. Those who study the natural world and use experience and reason to explain why things happen are called 'scientists'. 'Science' comes from the Latin word ' _scientia_ ' meaning knowledge. There are many different types of scientists as there are so many things for us to inquire about. They include cosmologists and astronomers, who study the origins of the Universe, its galaxies, solar systems and planets. There are geologists, who study the Earth's natural features, and biologists, who study living things.

Those who use experience and reason to work out broader issues, such as how we know things, what you should do to be a good person and whether we really exist are called 'philosophers.' Those who also use faith to work these things out are called 'theologians'. They all have something to offer us, so you shouldn't be too hard on the ones you don't agree with.

iii

One of the main issues that occupies all these people is whether knowledge is innate, meaning it's something we're born with, or learned after we are born. We know some things as soon as we are born. As soon as you and Tom were born, you both knew how to cry to get attention and to feed. These things are part of the instinctive knowledge we are born with to help us survive. Other things take a while to learn, like how to walk and talk.

We can see this in other animals too. Every year, we are visited by a large cuckoo, the Koel. Cuckoos are parasites: they lay their eggs in other bird's nests and get them to raise their young. Koels live in northern Australia, New Guinea, Timor and the Solomon Islands and migrate to Sydney in summer. After the Koels arrive, they lay their eggs and then leave before their young hatch. Somehow, their young are able to find their way back home in the north. We often explain that as instinctive knowledge. But no-one really knows how they manage it. It's another grey area.

iv

All these grey areas have encouraged some people to believe that as we don't know anything for certain all things, and opinions about, them are equal. We call this belief 'relativism'. One of the reasons I wrote this little book for you is so you can deal with this argument – as all things and opinions are certainly not equal, not by a long shot. Relativism can be quite useful. We should treat everybody equally and in the way we hope they would treat us.

But it can also be quite dangerous. Many people use it to justify arguments that are flat out wrong. They do this by, for example, distorting the truth about what happened in the past. They'll say something never happened when it really did. But when you look closely at their argument, you will see they either have no evidence for it or they have lied about the evidence they claim to have.

That is an extreme example. The difficulty is that we often don't know what happened in the past as we do not have adequate sources. But, especially in modern times, we usually we have enough to give us a reasonable idea of what occurred.

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**II. The Universe**

i

No-one really knows how we got here. So let's start with some names. Everything there ever is and everything there ever was is called the 'Cosmos'. Cosmos was one of the gods of ancient Greece. The Greeks believed everything was once a formless mess called 'Chaos'. Then, a very long time ago, Cosmos emerged from Chaos. It's a bit like the lounge room after one of your birthday parties. The table is covered in plates and glasses and there is wrapping paper all over the floor. This is chaos. Then we clean everything up and chaos becomes cosmos. We'll hear more about the Greeks later. They were very clever and interested in everything around them.

We don't use the word 'cosmos' much anymore. Instead, we usually call everything that exists now 'the Universe'. We don't really know what it looks like - there's no where to stand and get a look at it from the outside. If you got in a space ship and travelled forever, you would never reach the edge of the Universe. As far as we know, it's infinite, or endless. We have sent up space ships to take photos of it. But they can never show us the whole thing as there is nowhere to see it all from and, it appears, most of it is invisible.

ii

Before the Universe existed, there was nothing. That's a bit hard to believe: if there was nothing, where did the stuff that makes up the Universe come from ? Maybe there was a universe before ours and it collapsed and ours was made up from the bits left over. Or maybe there are other universes and ours budded off from one of them, like a flower on the branches of one of our camellias.

This is what we think happened. About 13.5 billion years ago, the Universe came into being. We call this the 'Big Bang'. We don't really know what happened. It seems that a tiny, dense piece of matter suddenly inflated like a huge balloon. Whatever happened, it produced the particles that make up 'atoms'. Atoms are the minute particles from which everything is made. The first type of atom to emerge from the Big Bang was a matter called 'hydrogen'. The particles that make up atoms have names too. But they keep changing, as we're not sure exactly what they are yet.

The Big Bang also produced the physical forces that hold the Universe together. The most important force is gravity. It is the attractive force that all things have. You usually only notice it when you put something very small, like an apple, near something very big, like a planet. As the planet has much more gravity than the apple, the apple is drawn to the planet. So if you picked up an apple and let it go, it would fall to the ground as the Earth's gravity is stronger than the apple's and pulls it down. If there was no gravity, we would all float up into the sky.

We think the same forces that hold the Universe together are the same ones that hold atoms together. But no-one really knows if that's true. Some of the particles that make up atoms do strange things. Some of them can appear in two places at once. So it might be best if we start with what we think we know.

iii

Even something as tiny as a hydrogen atom has gravity. After the Big Bang, one hydrogen atom was drawn to another. Then they were joined by another. And then another. Eventually, the hydrogen atoms formed enormous clouds which we call 'nebulae'.

Clumps of hydrogen atoms formed inside these nebulae. Over time, some of these clumps became so huge that some the atoms in the middle were crushed and got stuck together. We call this process 'fusion'. Two things happened when two hydrogen atoms fuse together. Firstly, they form a new type of atom called helium. Secondly, they give off a burst of light and energy, which we call 'radiation'. If enough hydrogen atoms fuse together in one of these clumps, they turn into a star. This happened to billions and billions of clumps of hydrogen atoms, creating billions and billions of stars. This is what formed all the stars we can see at night. Gradually, some nebulae turned into groups of stars, which we call 'galaxies'.

There is one very special star that we can see every day. Our Sun is a star. It shines up in the sky and keeps us warm because all the tiny hydrogen atoms in its core are still getting squashed and fusing into helium, giving off radiation. We call this radiation 'sunlight'. We use it to heat out water at home by catching some of it with the solar panels on the roof. As sunlight can burn you it's important to wear your hat and put on block-out, especially during summer, when the Sun closer to us.

iv

You might be wondering why, after the Big Bang, all the hydrogen atoms didn't just all get drawn back together into one, big clump instead of lots of separate clumps. It seems that that force of the Big Bang was so strong that it kept all the atoms moving away from each other and so allowed individual stars to form. This movement is still happening now. As far as we can tell, everything is still moving apart.

But that's not the whole story. The nebulae and stars need more than gravity to hold together. In the 1930s Fritz Zwicky, an astronomer, argued that if you work out the total mass of a galaxy, it turned out to be much more than the mass of all the stars it contains. So there had to be something else there. Since no-one could see whatever it was, Zwicky called it 'dark matter'. If we apply this to the Universe as a whole, it turns out that about three fifths of it might be made of dark matter. Apart from that, we don't know much about it.

Whatever is holding the Universe together, it hasn't stopped many stars gathering around one another until they made up enormous clusters. In some of these clusters, the stars are not very close together. But because they are so far away from Earth, it looks to us that they are all clumped together. Some of the star clusters we can see from our backyard include the Pleiades and Omega Centauri.

v

The stars in a galaxy are much closer together. This brings us closer to home: our Sun is one of the billions and billions of stars in a galaxy known as the Milky Way.

If you were to find a place from which you could look down on the Milky Way, it would look like a beautiful white spiral. Our Sun is located out way out in one of the arms of this spiral. It's called the Orion Arm. It got its name from the Greeks. If we go outside on a clear, dark night in the summer, we can see a large, rectangular group of stars. Inside this rectangle is a row of three bright, white stars. Just above them is a fuzzy patch of light. The Greeks thought this group of stars looked like a man from one of their legends, Orion. He was placed up in the sky by the gods after he was stung by a scorpion. The stars in Orion are in the same arm of the Milky Way as the Sun. So that's why it's called the Orion Arm.

As for the three bright stars inside the rectangle, that's Orion's belt. The fuzzy patch above his belt is a nebulae. If you look at it through our telescope you will be able to see some new stars emerging.

Orion's not up there all by himself. On the other side of the sky, is the scorpion, Scorpio. If you go out on a winter's night, you will see its curled tail – ready to strike if Orion comes too close. If you look towards Scorpio's tail, you will see a thin, white band that arcs across the sky. This is the Milky Way – our galaxy. If you look just below Scorpio's tail, there is a patch that seems a bit brighter that the rest. That is the centre of the Milky Way.

As the galaxies are very big, they have a lot of gravity. The bigger ones pull them smaller ones towards them, forming clusters of galaxies (or 'galactic clusters'). The Milky Way is part of one of those clusters, called the 'Local Cluster'. On a clear night, you can see two patches of light that look like they have broken off the Milky Way. They are the Magellanic Clouds \- two galaxies that are part of the Local Group just like the Milky Way. If you wait until late October and stay up late enough, you can see the Andromeda Galaxy. It is also part of the Local Group, and is the closest galaxy to us. Some scientists think it will crash into the Milky Way – but that won't happen for millions and millions of years.

The big clusters of galaxies themselves have clumped together into even bigger groups, known as superclusters. Our Local Cluster is part of the Virgo Supercluster. Now that we've mapped out the Universe, let's have a closer look at the stars.

vi

If we look up at the night sky, we can see that some of the stars are orange, some yellow, some blue and many are white. This is because there are different types of stars. Their colour is often a clue to how big they are. The biggest of them all are the orange ones, like Betelgeuse in Orion and Antares in Scorpio. They are red supergiants: Antares is about 800 times the size of our Sun. Some of the blue ones are also pretty big. The star Rigel, which is in Orion, is a blue supergiant.

When a supergiant runs out of the hydrogen that keeps fusion happening, it collapses in on itself and explodes with enormous force. This is called a 'supernova'. It's one of the biggest, most dramatic and destructive events in the Universe. Way back in 1987, Mummy and Daddy both saw the last supernova easily visible from Earth. A blue supergiant in the Large Magellanic Cloud blew up. We could see the explosion from Earth - it looked like a small orange star.

After it's exploded, a supergiant star may go on to form a neutron star. It may then become a pulsar, a type of dying star that spins very quickly and gives of regular pulses of light and energy. Some big stars turn into something called a black hole. A black hole is like the drain at the bottom of the bath. Say you put in the plug, fill the bath with water and put Captain Duckie in. When you pull the plug, Captain Duckie gets pulled towards the drain, as all the water is being sucked down into it. Black holes pull things towards them, just like the drain.

But they are much more powerful - so powerful that they can suck in beams of light. It may be that black holes are important for holding parts of the Universe in place. While gravity is a strong force, no-one is sure if it is strong enough to keep a whole galaxy together. But a black hole is. So it may be that there is a black hole in the middle of every galaxy, drawing all the stars towards to it to...well, no-one knows.

Luckily, our Sun is a different type of star called a yellow dwarf. These are the best stars to live near as have enough hydrogen to power them for about a billion years. This is good for us, as it means the Sun will last a long time. But when it starts to run out of hydrogen, about five billion years from now, it will start to expand and become a red giant. By then, it will be too hot to live on Earth. So hopefully people have found somewhere else to live by then. After it has burnt up its fuel, the Sun will shrink from being a red giant to being a white dwarf. After that, it may fade into becoming a black dwarf. But no-one's really sure, as the Universe is not old enough for any black dwarfs to have formed yet.

Some stars seem to vanish, then re-appear at regular intervals. They are called 'variable' stars as their brightness varies. In winter one year, I was looking at a group of stars called Leo, as it looks like a lion. It seemed to me that it had one star too many. I thought it might be a supernova, so checked my atlas. But it was a variable star called R Leonis going through its bright phase. No-one is sure why their brightness varies.

When we look at these things in the sky, we don't actually see them as they appear now. They are so far away that the light they give off takes a very long time to reach us. In fact, they are so far away that we measure the distance between them and us using a unit called a 'light year'. A light year is the distance light travels in one year. Light travels very quickly. When you turn on the lights at home, they come on immediately. You cannot see the light moving because it is so fast – about 300,000 km each second.

This gives us some idea how big the Universe is. The Andromeda Galaxy, for example, I about 2,500,000 light years away. So when you look at it, you are seeing it as it was that long ago. That means we are seeing it as it appeared 2,500,000 years ago.

vii

Stars are one of the building blocks of the Universe. They mark our beginning, our end and everything in between. Everything you are made of and that you see was made in a star. How did that happen ? Do you remember how stars light up when the hydrogen atoms in their centres get squashed together, fuse and make helium ? That process continues while the star burns thought its supply of hydrogen. The helium atoms get squashed and make bigger atoms. These bigger atoms get squashed together and make even bigger atoms. These other types of atoms include oxygen, which makes up part of the air we breathe; calcium, which makes up our teeth; and copper, which we use to make coins. These things are called 'elements'. An element is something that is made up of one type of atom. So a piece of pure gold, for example, is made up only of gold atoms.

Nothing can live on a star - they're too hot. Instead, we live on a planet called Earth. It's one of the eight or nine planets that orbit the Sun. Earth, the Sun, the other planets and a few other things are all known as the 'Solar System'.

Earth is our place in the Universe. If there is another universe and someone there wanted to send you a post card, this would be your address:

Eleanor Cahill,

Lindfield, New South Wales, Australia,

The Earth, The Solar System,

Orion Arm, Milky Way Galaxy,

Local Cluster, Virgo Supercluster,

It seems there is no-one to send you this postcard. Earth is not just special to us because it's our home. It's special for another reason: as far as we know it's the only place where there's life. You'd expect that with so many stars in the sky and so many galaxies in the Universe that there would be lots of life. Frank Drake and Carl Sagan, the astronomers, reasoned that since there were so many stars in the Milky Way, even if only a tiny percentage of them had planets that supported an advanced civilisation, we would have a lot of neighbours. But so far we haven't found any and no-one else has found us. But while it seems we're alone in the Universe, Earth has a very interesting family. Let's have a closer look at our Solar System.

viii

Like a lot of other things, we're not really sure how the Solar System and planets were made. Stars grew out of clumps of hydrogen atoms the formed in nebulae. It seems that planets were made out of the bits and pieces left over when a star was forming. These bits and pieces formed a plate-shaped disc around it. As they circled around the new star, they collided together, broke up and reformed until they gradually grew bigger and bigger. At various intervals from the Sun, the bigger pieces grew so large that they dominated a particular orbit around the Sun. Eventually, the ones that survived became planets. We think this happened about 4.5 billion years ago. This was about 9 billion years after the Big Bang. So the Universe was already pretty old by the time the Sun and planets came along.

One day, when I was on the way to work on the train, I thought of another way solar systems may have been formed. Stars often come in pairs, called 'binary stars'. It seems that the clump of hydrogen from which they are formed split in half, making two stars instead of one. They orbit about a common point between them. It occurred to me that if one of the pair failed to light up, then the bits and pieces let over from it would start to orbit the other star and eventually form planets. In other words, I wondered if all solar systems were failed binary stars. But I later found it wasn't a new idea at all: an astronomer, Gerard Kuiper, had already thought of it.

If we were flying high enough above the Solar System and looked down on in, we would be able to see eight planets going around the Sun. The one closest to the Sun is Mercury. The next one is Venus. After Venus is Earth. Then comes Mars, Saturn, Uranus and Neptune.

Not long ago, there was another planet called Pluto. But many of the people who study the Solar System decided it was not really a planet, but just one of a band of 'dwarf planets' that orbit the Sun way out past Neptune. As Kuiper predicted the existence of this band, it is called the 'Kuiper Belt'. So while Pluto and the other dwarf planets are still part of the Solar System, they're not counted as planets anymore, but 'Kuiper Belt objects'.

If we go even further out from the Sun, past the dwarf planets, it seems that there is another group of objects which we call the 'Oort Cloud'. These objects are mostly chunks of rocky ice. They orbit the Sun just like the planets. But every so often, one of them is pulled towards the Sun and becomes a 'comet'.

Comet is Greek for 'long-haired star'. They got this name because of what happens to them when they get close to the Sun. As the comet gets closer and closer, its surface ice warms up and starts to melt. The force of the Sun's rays blows the melted ice out to form a long tail. The most famous comet is called Halley's Comet, which passes Earth every 76 years. We both saw it when it last arrived in 1986. While everyone thought it would be very bright, it wasn't that impressive. In 2007 another comet, Comet McNaught, passed the Earth. It was much more impressive than Halley's Comet – it became very bright and grew a long tail that stretch across a large part of the sky.

We leaned quite a lot about the Sun, planets, asteroids and comets over the last forty years as we've sent out space ships to look at them. But there is still a lot we don't know. Your cousin, Henrik, is trying to find out more about how the solar system works. But even though he's clever as a Greek, there are many things about them even he cannot explain.

ix

We can see many of the plants in our Solar System from our backyard. They look like brightly-coloured stars. But unlike the stars, the planets move quickly across the sky: 'planet' is from the Greek for 'wandering stars'. The stars, like Antares, move too - but they are so far away we can barely see it happen.

Each of the planets has some remarkable feature that tells us something about the Solar System. One day, people will visit them to see these incredible things – just like we go to the Blue Mountains or Fiordland to see the beautiful scenery.

The planet closest to the Sun is Mercury. It's the smallest planet and looks like a small reddish-brown star. Now since Mercury is so close to the Sun, it never rises very far above the horizon. So if we want to see it, we have to get up before the Sun rises and find somewhere with a good view of the eastern horizon. As Mercury is so close to the Sun, it's very hot there - too hot for us to travel there and stand on it.

Mercury is a rocky world covered in craters. The craters are reminders of the time when the Solar System was very young. At that time, there were lots and lots of chunks of rock and ice orbiting the sun. We call them 'asteroids'. There are still some left. But long ago there were so many more that they would often crash into the surface of the planet, leaving a big crater. This is what's happened on Mercury and shows that its surface has not changed since the time when there were more asteroids.

The next planet is Venus. From our house Venus looks like a bright, white star. But up close Venus is not as nice. It is covered with thick clouds of poisonous gases. Its air is very dense and the ground is too hot to walk on. So if you tried to walk around on Venus unprotected, you'd be squashed and burnt up by the pressure and heat. Unlike Mercury, there are not many craters on Venus. This is because of an interesting feature many planets have, volcanoes.

A volcano is a big hole in the surface of a planet. Not every planet has them, just the ones with a solid surface. Imagine a planet is like a peach. The surface of a planet is like the skin. Under the surface of a planet is melted, liquid rock called 'magma'. It's a bit like the peach's flesh. In the middle of a planet is a hard, metallic core, like the stone in the middle. In some parts of the surface of a planet, a hole forms and lets some of the magma escape. That hole is a volcano. It's a bit like when you cut into a peach and some of the juice flows out through the skin. Except the magma is liquid rock. So it's very hot. Venus has many volcanos. They have let out so much magma that it's run all over the planet's surface and covered up most of the craters.

After Venus comes our planet, Earth. We'll come back to Earth soon. The next planet is Mars. In the night sky Mars looks like a bright orange-red star. It has the Solar System's biggest volcano, called Olympus Mons. Mars also has one of the Solar System's deepest valleys, called Valles Marineris. The fact that Mars has valleys, especially such a big one as this, shows that Mars may have once looked like Earth.

On Earth, valleys are formed when rivers of water cut into the crust. Over time this carves a big gash in the surface, which we call a valley. If there are valleys on Mars, it may once have had large rivers of water. This is also important as where there's water, there's often life. But conditions on Mars changed. Now, it's just a wind-swept desert. The only water it has now is found at its poles, where it had frozen into ice. Sometimes, when Mars is closer to Earth than usual, you can see its poles though my telescope.

Mars has another interesting feature: it has two little moons that orbit around it. They're called Phobos and Deimus. They are very small, rocky worlds. Phobos has a huge crater on it. So it must have been hit by a large asteroid at some point. It's likely that both Phobos and Deimus were asteroids captured by Mars' gravitational field and fell into orbit around it.

x

Mercury, Venus, Earth and Mars are all rocky planets. But the next few planets are very different. They are made from gas and ice. But before we get to the next planet, do you remembers how I mentioned there were still a few asteroids left over from when the Solar System was formed ? Most of them orbit the Sun between Mars and the next planet, Jupiter. As there's quite a few of them there, that part of the Solar System is called the 'Asteroid Belt'. Why they're there is unknown. Usually, when there are lots of small pieces of rock and ice in the same orbit, gravity pulls them together and they make a planet. But that hasn't happened in the Asteroid Belt. It may be that there was originally a planet there, but it got hit by a huge asteroid and was smashed up. Maybe it didn't happen that long ago, so the asteroids haven't had time to form into a planet yet. No-one is sure.

But we know a bit more about what they looked like. Just recently, we have sent a probe to take photos of one of the largest asteroids, called Vesta. They show it has some craters on it. So the Solar System must have been very crowded with asteroids at some point.

After the Asteroid Belt comes Jupiter, the biggest planet of them all. From our house it looks like a big golden yellow star. Unlike the rocky planets, such as Mars, you can't walk on Jupiter. It has a middle bit that's quite solid. But the entire planet is covered in a very thick layer of brightly coloured clouds of poisonous gas. In my telescope, you can see some light brown stripes on Jupiter's surface. These are some of the layers of clouds in its sky. Occasionally, these clouds are torn apart by fierce storms. One of these storms is so big that we can see it from Earth. It looks like a big red spot on Jupiter's surface: so we call it the 'Big Red Spot'.

Jupiter has quite a few moons. Four of them are so big that you can see them through a pair of binoculars. They look like small white stars near Jupiter. One of the largest moons is Io. It is has the most volcanos in the Solar System. The reason for this is that Io is very close to Jupiter. As Jupiter is so big, poor Io gets squeezed hard by Jupiter's gravity. This cracks it's crusts in lots of places, letting out lots of magma. Jupiter squeezes out so much of Io's magma that its surface looks different every time we send a space ship to look at it. Another one of Jupiter's large moons, Europa, is very smooth and covered in ice. Some think that under the ice there is a deep ocean of liquid water that may hold new creatures we haven't seen before. But no-one knows yet.

Apart from its moons, Jupiter also shares its orbit with some asteroids. As they run just in front of it and just behind Jupiter, they are safe from the pull of Jupiter's gravity. But many other bits and pieces left over from the Solar System are not as safe. As Jupiter is so big and has such strong gravity, it acts like a big vacuum cleaner and sucks up many stray asteroids and comets. We were first able to witness this in 1994, when Jupiter was hit by fragments of a large comet. This is good for us, as it means there are fewer of them around that might hit Earth: this has happened before with devastating results. It could happen again as there are still random bits and pieces floating around in the Solar System.

After Jupiter comes the most beautiful planet, Saturn. In the nigh sky, Saturn looks like a pale gold star. It is a lot like Jupiter, having a solid middle and a think layer of poisonous clouds. Through a telescope, you can see that it is surrounded by an extraordinary system of rings. They are made from pieces of ice and rock that orbit around Saturn. No-one really knows how they got there. Even Henrik, who has studied Saturn for years, cannot work them out. There may have once been some large asteroids circling Saturn that hit one another, leaving billions and billions of pieces of rock and ice that formed the rings. Why they didn't all merge together and form something else is unknown. They remain in orbit too far away from Saturn to be pulled in by it's gravity, but too close to escape.

Saturn has many moons - every piece of ice and rock in Saturn's rings is a tiny moon. But the most interesting one is Triton. It is the only moon in the whole Solar System with a think atmosphere and with pools of liquid on it. Some think this is what Earth may have looked like when it was younger. So there might be life there.

After Saturn comes Uranus. It's quite big, but so far away that it looks like a faint blue-green star. Uranus is covered with thick clouds. But under the clouds, there may be oceans. But they are not oceans of water, like we can see at the beach. Instead, they are oceans of frozen gas: far too cold for anyone to swim in. Uranus also has many moons. The oddest one is Miranda. Poor Miranda looks like it broke when someone dropped it and wasn't put back together very well. No-one is sure why it looks like this. Some say an asteroid hit Miranda so hard that it shattered. Then all the bits were drawn back together by each other's gravity. Others say it is because it's crust moved, leaving huge canyons on its surface.

After Uranus comes Neptune. It is so far away that we can't see without a telescope. It is a large, deep blue planet. For a long time, people thought that as Neptune is so far from the Sun that it must be frozen solid. But it has a sky just like Earth. But unlike Earth, its sky is filled with clouds of toxic gases blown around by very strong winds and storms. One of these storms is like Jupiter's Great Red Spot - it's called the 'Great Dark Spot'. Neptune also has oceans: but they are made of frozen gases, just like those on Uranus. It has many moons, but none of them have any interesting features.

Incidentally, Jupiter, Uranus and Neptune also have rings around them, but none of them are as stunning as Saturn's.

Finally, there is Pluto. Or I suppose I should say there was Pluto, as it is now said to be a dwarf planet or a Kupiter Belt object. Nobody knows how many dwarf planets there are. But some of the ones found so far have been very big, even bigger than Pluto. But Pluto is still quite interesting. Even though it is quite small, it has three moons. As it is so far away, we hardly know anything about it. But we've sent a space ship out to have a look at it. That ship will arrive in 2015 – when you are four !

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For a long time, the Solar System was the only one we knew about. Many people had wondered if there were any other solars systems out in the Universe with their own planets like ours. Then, in 1992, one was found orbiting a pulsar. At the time I write this (2011) about 570 planets have been found orbiting other stars. Some of them are still being formed, which gives us some idea of how our own Solar System developed. But at the moment we don't know much about them yet as they are so far away. Who knows what amazing things they have to tell us. I wonder if anyone lives on them.

Now it's time to visit the most interesting planet of them all – ours.

**III. Earth**

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We have told you the story of Goldilocks and the three Bears. Remember how the Little Bear's chair, porridge and bed were all "just right" for Goldilocks ? It turns out that the Earth is just right for us. We have the right kind of star: our Sun is a yellow dwarf, so it burns slowly and very steadily. This is much better than having a Red or Blue Giant for our sun. They blow up after only a few million years. So they wouldn't be much use to us.

We're also lucky to have large planets like Jupiter and Saturn nearby. As they are so big, they have very strong gravity fields and sweep up many of the asteroids that might hit Earth. This doesn't always happen. Just last year (2013), a small asteroid fell near Chelyabinsk in Russia. If it had been any bigger, it could have wiped out the city. When an asteroid falls to the Earth, it is called a 'meteor'. As we'll see a bit later on, Russia has been hit by a few meteors recently.

Then there is Earth's location in the Solar System. It's is not too close to the Sun, so it's not too hot. And it's not too far away, so it's not too cold.

Earth has a moon, like most of the other planets. Most days, you can see it outside. It looks best at night, when it glows against the darkness. The Moon was probably once part of Earth. It seems that when Earth was very young, a planet or large aasteroid hit it (scientists call this object 'Thiera'). The bits of Earth blown out into space by the impact fell into orbit around it, then joined together to form the Moon.

Up close it is a grey, dusty world covered in craters. It is the only place in the Solar System that we've visited in person. The first astronauts landed there in 1969. The last ones visited in 1972, after I was born. Sadly, we don't go there anymore as it's too expensive.

The Moon is important to us as it is just the right distance away to help keep Earth balanced in its orbit around the Sun. The Moon's gravity also stops it from rotating too quickly, so the length of our days stays the same. Lastly, it causes the tides to rise and fall. When we go to the beach and see the tide coming in, it's a reminder how strong the Moon's gravity is, even though it is so far away.

Speaking of things far away, even though we are far away from the Sun, all stars give off rays that burn our skin. This is what happens when you get sunburnt. If you ever want to see what happens when you get badly sunburnt, just have a look at my back !

My sunburn would have been much, much worse except for one thing. Deep inside the Earth is a layer of melted rock, magma, which swirls around Earth's core. This movement generates an electrical field that protects us from most, but not all, of the Sun's rays. This field, the magnetosphere, makes it easier for life to survive on Earth. If you are standing near the North or South Poles, you can see it at work.

Apart from light, the Sun also gives off something called the solar wind. It is a stream of particles charged with electricity. When the solar wind hits the magnetosphere around the North and South poles, the charged particles give off spectacular bursts of green and purple light. These light shows are called 'aurora.' If the magnetosphere was not there, all these particles would hit Earth and burn us to a crisp. So, like Goldilocks, we've been very lucky.

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As for the Earth itself, it was formed at the same time as all the other planets in the Solar System about 4.5 billion years ago. It started off as a collection of chunks of rock left over from the formation of the Sun. Over billions of years, gravity brought these chunks together. Many, many times Earth was hit by asteroids and comets, which carried elements as copper, carbon and oxygen to Earth. Carbon and Oxygen are particularly important to us as they are the building blocks of life.

But before we can have life, we need something else – an 'atmosphere'. As the Earth cooled down, some of the gases it contained accumulated high above the surface. As the pressure built up in the atmosphere, it sparked off storms. Over millions of years, it rained so often that much of the Earth was eventually covered in water. And often where there's water, there's life.

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No-one really knows how life developed here. There are several different explanations. Some say it was thanks to the elements carried to Earth by the asteroids and comets that crashed into it. Those elements were then struck by lightning to form the compounds that make up living things. Others believe a god created all living things.

Then there is the related question of why life developed at all. Some say it was a random chance. Others believe a god created us for some special purpose or as part of a plan. Who do you think might be right ? Let's look more closely at some of these ideas.

Some people think life began here as Earth has large supplies of certain elements, such as hydrogen and oxygen. Other types of materials necessary for life include methane and ammonium. Methane is a gas we use to cook our food with. Ammonium is a chemical we use to clean the bathroom. These types of material are called 'compounds.' They are different from elements as they are made up of more than one type of atom. Water is, for example, a compound made up of 2 hydrogen atoms and 1 oxygen atom. Often when we talk about elements and compounds, we call them 'chemicals'.

When all these chemicals are all in the same place at the same time, they can form more complex chemicals that are the building blocks of life. To make these complex chemicals, you need heat or electricity. Millions of years ago, Earth was much hotter than it is now. And there was plenty of electricity around – it came from the lightning storms that tore through the atmosphere. So conditions may have been right to form these complex chemicals.

As there was no-one around millions of years ago, we can't be sure this is what happened. In the early 1950s two scientists, Stanley Miller and Harold Urey, decided to re-create the conditions found on Earth millions of years ago to see if they could make these complex chemicals.

They mixed some water, hydrogen, methane and ammonium in a big glass jar. To mimic the effects of lightening, they ran an electric current through this mixture. After a while, the mixture turned a dark brown colour. This happened because many different types of complex chemicals necessary for life had formed in the mixture.

Miller and Urey reasoned that if they could create these chemicals in a big jar, then they could have formed naturally on Earth. In other words, they showed the building blocks of life could have formed here naturally millions of year ago. This is an example of knowledge gained by induction: Miller and Urey reasoned from the specific to the general based on things they had experienced by observing them.

Miller and Urey's experiment was very ingenious. But it is a big step from making chemicals in a jar to forming a living creature. How does a collection of chemicals come to life ? While no-one knows for certain, many people believe things they cannot see or explain as they are happy to accept them on faith. While many believe a god created life, no-one has been able to prove a god exists. Then again, no-one has been able to prove a god does not exist. It's not something that can be demonstrated the same way Miller and Urey showed how complex chemicals could have formed. But they did show you do not need a god to make the complex chemicals necessary for life. You just need some stuff from the kitchen and laundry, an electric current and a big jar.

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Faith is an important part of our culture. So even if you do not accept it as a source of knowledge, it deserves some respect. At the beginning of human history, people did not know why the stars shone, what made the Sun rise and set, what caused the seasons, where rain came from or what caused disease. The only answers they could think of were that something much more powerful that them caused all these things to happen. They called these things 'gods'.

So what does a god look like ? No-one knows, as they cannot be seen. Many people thought they must look like us. So some of the earliest art works shows gods shaped like people. But as a Greek philosopher, Xenophanes of Colophon, pointed out, we only think this as were human. If horses, lions and cattle could draw, they would draw gods that looked like them.

Some groups of people had many different gods – one for each thing they could not explain. So they had, for example, a god for the planets, for the Sun, the seasons, and the ocean. But there was one group of people who had only one god. They are important to our story as we have inherited some of their culture. They are also important as you are distantly related to them. They are the Jews. Many hundreds of years ago they wrote a book about their god, which we call the Bible.

The Bible is made up of a number of short books. The first book is called 'Genesis': ('genesis' is the Greek word for origins). In Genesis, the Jews describe how their god made Earth:

" _In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep...And God said, Let there be light: and there was light....and God divided the light from the darkness. And God called the light Day, and the darkness he called Night..._

And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters. And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so. And God called the firmament Heaven...

And God said, Let the waters under the heaven be gathered together unto one place, and let the dry land appear: and it was so. And God called the dry land Earth; and the gathering together of the waters called he Seas:...

And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so....

And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years: And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so...

And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven. And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind:...

And God said, Let the earth bring forth the living creature after his kind, cattle, and creeping thing, and beast of the earth after his kind: and it was so...

_And God said, Let us make man in our image, after our likeness... So God created man in his own image, in the image of God created he him; male and female created he them_."

Many other cultures have a similar account. The Greeks had their story about Chaos and Cosmos. The Māori, who are also distantly related to you, have a similar story. They believed everything began with Ranginui, the Sky god, and Papatuanuku, the Earth god.

Ranginui and Papatuanuku were a couple and had many children. But as Ranginui and Papatuanuku lay embraced together, all their children lived in the dark. After a while, they got tired of this. One of them, Tāne, suggested they push their parents apart to let the light in. Some of the others tried to push them apart, but failed. Then Tāne lay down on his back and pushed them apart with his legs. When they parted, Ranginui and Papatuanuku began to cry, which is why it rains.

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These stories are very important to us. But they don't explain how everything happened. The Book of Genesis says God made everything in six days. But many people wondered about this: as six days is not a lot of time to do so much.

James Ussher, an Archbishop from Ireland, read through the whole Bible, added up all the time it described and calculated that everything was created in 4004BC, about 6015 years ago. A while later John Lightfoot, a university vice-chancellor, worked over Archbishop Ussher's sums and decided God created the Universe at 9am on Sunday 23 October 4004BC. This was a good time to start everything, as it was just after breakfast on the (first) weekend.

That's pretty much all we know about the beginning of the Universe, the Solar System and the planets. But before we move onto what happened next, I need to tell you the story of Noah's Ark, which is also in Genesis.

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You already know about Noah. In your bedroom, you have a Noah's Ark mobile and one of your jigsaw puzzles is all about Noah, his wife and all their animals. Their story goes something like this.

A long time ago, God saw that many people were not very nice to one another. Their wicked, evil ways made him so angry that he regretted creating them. So he decided to flood the whole Earth and start again.

But there was one man God still liked: Noah. So he warned Noah of his plans and told him to build a big ship called an Ark. On this ship, Noah was to load his family and two of every animal so they would survive the flood. Noah did as he was told. As soon as the Ark was loaded up, the rains came. Forty days and forty nights, the world was flooded so deep that the waters covered the highest mountains.

When everything was washed away, God stopped the rain. Noah landed the Ark on a Mount Arrart, in Turkey, and sent out a raven to see if there was any dry land for everyone to walk on. But as the raven didn't come back, Noah couldn't tell if it was safe to leave the Ark. This, by the way, shows you how clever ravens are. The poor bird had been cooped up in the Ark for weeks and was probably very happy to get away.

So Noah sent out a dove. After flying around for a while, the dove found an olive tree, pulled off some leaves and brought them back to Noah. This told Noah that the floods had drained away and they could start unloading all the animals. By this time, God had begun to regret what he'd done and promised " _I will not again curse the ground any more for man's sake...neither will I again smite any more every thing living, as I have done_." As sign of this promise, God lit up the sky with a huge rainbow.

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For a very long time, many people believed what it said in Genesis. They thought Earth was made about 6000 years ago. Many thought the story of Noah's Ark explained why some things that once lived on Earth were extinct as they were all washed away in the flood. They also thought it explained why you often find sea-shells on mountains: they assumed they had been dumped there when the mountains were under water.

Gradually, scientists worked out that 6000 years was not long enough to account for some of the things they observed. One of the first to have some doubts was the geologist William Smith. He noticed that when he dug into the Earth, he founds many different layers of rocks. He assumed the lower layers of rock must be the oldest as they were laid down first. Smith also found that some of the layers held the remains of different types of plants and animals that had been preserved in the rock. We call these remains 'fossils'. Smith used them to identify the various layers and work out the order in which they had been deposited. He noticed that some of the fossils in the lower layers were not found in the layers closer to the surface. It was as if those creatures had vanished.

A French naturalist, Georges Cuvier, heard about Smith's work. He argued that the absence of some fossils in younger layers of rock showed there must have been several natural catastrophes that wiped them out. But Genesis only mentions one flood, the one from Noah's time. Some began to wonder if Genesis was correct.

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This led some to query how long it would take for all the layers of rock to form. Two geologists, James Hutton and Charles Lyell, argued that we can work out how this happened by assuming that the forces that created them were the same forces that had been active since the Earth was formed. In other words, they believed " _the present is the key to the past_."

The main forces that created the Earth's features are the movement of water and the movement of the Earth's crust. Let's look at some examples. When a river runs over the Earth, it wears away some of the rock over which it passes. Often, it dumps this material somewhere else. These processes are called 'erosion' (the wearing away) and 'deposition' (the dumping). Over a long, long time, the river gradually carved a deep trench into the Earth. We call that trench a valley. We live near a famous example of a valley. It's at Wolli Creek, where Nana, Grandad and the rest of us used to live. What happened there is that over millions of years, the small creek eroded the sandstone rock it ran over, carving out a deep trench.

When the Earth's crust moves, it may form mountains. This is because the crust is made up of separate sections called 'plates'. When these plates come together, there are two things that can happen. One plate might slide underneath the other. That forms a feature called a 'trench'. Or the edges of the plates both push up the ground, forming mountains. When the plate that India sits on collided with the plate China is on, the edges of the plates were forced up, leaving the Himalayan Mountains. The same thing happened when the plate New Zealand is on collided with the plate Australia is on - it pushed up the land to from a long range of beautiful mountains called the Southern Alps.

In other places, the plates rub together, causing the ground to move. This movement is known as an earthquake. This happens where the New Zealand and Australian plates collide: which is why New Zealand has so many earthquakes.

Hutton and Lyell reasoned that 6000 years was not enough time for natural forces to carve out a valley or for mountains ranges to form. Instead, they argued that as these forces worked so gradually, these things must have taken millions of years to happen.

Also, as they were created by natural forces, people began doubting whether God had really made the Earth. Some even doubted there was any God at all and claimed all the stories in Genesis were just myths.

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Another discovery made people think the Earth was older than Ussher or Lightfoot claimed. People who had been poking around in caves in Britain and western Europe found the bones of large animals that no longer existed, such as sabre-toothed tigers and mammoths. As these creatures weren't mentioned in Genesis, it was assumed they had drowned in the flood.

Sometimes these bones were found with mixed up with things people had made, such as stone tools. When these discoveries were made in the early 1800s, it had been a long time since anyone in Britain and Western Europe had bothered using stone tools. By the early 1800s, everyone was using metal tools. Then, in a cave in the Neanderthal Valley in Germany, someone found the bones of an early type of human. It was very different from us. It was quite solid and had a larger skull. There were none of these people still around.

These discoveries indicated the Earth was more than 6000 years old. Many were no longer satisfied with the account given in Genesis. Had God created everything in six days ? Had every living thing really survived only thanks to Noah's Ark ? We still don't now exactly what happened. But it may have been something like this.

**IV. Life**

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All life on Earth is made up of tiny things called 'cells'. They are much, much bigger than atoms, but they are still pretty small. Each cell is made up of many different parts, which are known as 'organelles'. Each organelle has a different function. In plant and algae cells, organelles called 'chloroplasts' use sunlight to turn gas into sugar, which they use to feed themselves. (Algae are a large group of living things: they include the seaweed we find washed up on the beach).

When a chloroplast makes itself some sugar, it breaks down a small amount of carbon dioxide (a gas made up of carbon and oxygen) and gives off a small amount of oxygen. We need oxygen so we can breathe and most of it comes from plants. So plants are very important to life on Earth.

Other types of cells do not have chloroplasts. These include the cells we are made up of. These cells rely on organelles called 'mitochondria' to produce their energy.

No-one really knows how cells came into existence. It is a big jump from the amino acids that Miller and Urey made and making something that is alive. One possible starting point may be the organelles. It may be that some of them were once independent creatures in their own right. Some organelles may have been swallowed up by others until, somehow, they were able to do something quite special: reproduce themselves.

Cells are the smallest, most basic living thing that can do this. There are smaller things that exist, called viruses. But they cannot reproduce themselves. Viruses are dangerous and sneaky. They carry diseases: the common cold that we get from time to time is a type of virus. They replicate themselves by invading animal cells and tricking them into making more viruses. The poor cell eventually makes so many viruses that it pops like a balloon, releasing all the nasty new viruses. So as something is only alive if it can reproduce itself, we do not consider viruses as living things.

Cells reproduce themselves by splitting in half. Basically, they divide themselves to create two new cells. We all start off as a single cell. It splits in half. Then those two cells divide to make four cells and the process goes on an on until you we are ready to be born.

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That simple process led to all the different types of plants and animals and other living things we have today. How that happened takes a bit more explaining. Each cell contains a compound called 'DNA'. A cell's DNA is like a tiny instruction manual that contains all the information needed to make that cell. They're a bit like the manuals that come with furniture from Ikea, except they are easier to read.

DNA is made up of a sequence of compounds, which we call genes. Every living thing has a different sequence of genes (unless it has been 'cloned': we'll come back to clones later). The genes found in each cell dictate what a living thing looks like. You, for example, have cells with the genes for blue eyes. Poppy has cells with the gene for brown eyes. Some people have the genes that give them one blue eye and one brown eye, but they are rare.

Depending on where a plant or animal lives, some genes are better to have than others. If it lives in a very cold place, it needs genes for features that help keep it warm. If it just happens to have a gene that gives it features that help it survive, it is more likely to survive and pass that gene to its off-spring. Other things that don't have those genes may not survive and become extinct.

This process works in every different kind of living thing. This is because the individual members of a population of a living thing are not identical. A few members have, by chance, a couple of different genes from the others. They include, for example, the people with the genes that give them one blue eye and one brown eye. We call these rare genes 'mutations'. The members of a population that have a mutation that helps them live in their environment are more likely to survive and have off-spring.

Over a long period of time, the survivors will accumulate many different mutations that will help them survive in their environment. During that time, they may change quite significantly and look nothing like how they started off. We call this process 'evolution by natural selection'. This is because the environment selects which things survive as it favours the ones who just happen to have mutations that give them features that better suit them to live in it.

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Evolution explains how living things develop, or 'evolve', over time. This is usually a slow process. But sometimes, it can happen quite quickly. In England there is a type of moth, the Peppered Moth, which has genes for being pale or being dark. So in the moth population, there are light-coloured ones and dark-coloured ones. They all lived in a forest where the trees had pale-coloured bark. This environment favoured the pale-coloured moths as they were camouflaged when they perched on the bark. When the dark coloured moths did this, they were easily seen and more likely to be eaten by birds. So the pale moths tended to survive.

Then one day, someone built a factory near the forest. Its chimneys belched out lots of smoke that covered the trees' bark in a dark layer of soot. When the pale moths perched on the darkened bark, they were more visible and easier for birds to find. The dark moths were luckier – they camouflaged when they perched on the dark bark. So more black moths survived than pale moths as the environment now favoured the dark moths.

But then things changed again. Laws were made to limit the air pollution for factories. Gradually, the trees' bark got lighter as there was less soot falling on them. So more light-coloured moths began to survive and the dark-coloured moths were back to where they started.

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This is very different from the account in Genesis about how God created life. Evolution by natural selection doesn't need a god to work. Instead, the dominant factor is the environment things live in.

Not everyone agrees with the idea of evolution. Ultimately, you will have to decide for yourself what you believe. All I will say is that you should look at all the evidence before you decide. Then, regardless of what you end up believing, at least you will have considered each alternative. Ultimately, there is a lot we do not know. So we should probably keep an open mind about things we don't fully understand.

We don't for example, know how cells developed and how the Earth ended up with so many different types of living things. Like many other things we've looked at so far, there was no-one around to see it happen. But some clues of what may have happened have survived. The oldest clues have been found scattered across Australia, England, Canada and China. Or I should say across where these lands are now, because they weren't always in the same place.

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The Earth's surface, or 'crust' as we often call it, is not as solid as it looks. It's pretty thin, floats on the magma underneath it and is broken up into plates. As the plates float on the magma, they move around quite a lot - although this happens very, very slowly.

So the land we're sitting on has moved over time. When the Earth was very young, it seems that all the land was clumped together into a big super-continent. People who study these things have called this super-continent 'Pangea'. But there was no-one around back then, so it didn't actually have a name: we just call it Pangea so everyone knows what we're talking about.

As the plates moved over many millions of years, Pangea broke up and the pieces of land that had once been Pangea joined together in different ways to form new super-continents. What is now Australia, New Zealand, Tasmania and Antarctica were all once parts of a super-continent known as 'Gondwana'. This kind of movement is still happening. Australia is very, very slowly moving towards Papua New Guinea.

Another important change that affects where land exists is the Earth's temperature. At certain times in its history, the Earth's temperature has dropped so low that huge parts of the oceans around the poles froze. As this caused the oceans to become shallower in some places, areas that had been covered by ocean were now dry land. When the Earth warmed up again, the ice at the poles melted, causing the oceans to rise again and flooding the land.

This last happened about 10,000 years ago, which isn't that long ago. The oceans at the poles froze and the seas became shallower. So, for example, the North Sea grew so shallow that some of the land between England and France was exposed and you could walk between them. The same thing happened in the Bering Strait between Russia and Alaska. It also happened between Papua New Guinea and Australia. So when the Earth warmed again, these areas were flooded and there was no more walking from one continent to the other.

This explains why not everything is found where it used to be and how some living things were able to travel over areas now covered in water. One way to keep track of everything is to imagine that you are watching a cartoon of the Earth changing over time. If you fast-forward the cartoon, you will be able to see the plates move and the poles freeze over and melt. If you look closely, you can see land come and go and things moving across it. If you look very closely, you will see that some of these things were quite odd.

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Cells are, as far as we know, the first forms of life. They are quite soft and have squishy walls that are easily torn. So if a cell has genes that give it some protection, it is less likely to get squashed. The first animals that we know of had genes that allowed them to build shells around themselves. They emerged sometime between 580 and 570 million years ago. There might have been things that lived before this time. But they have disappeared without a trace. They only reason we know about the shell-animals is that some of their shells were fossilised.

The shell-animals didn't have Earth all to themselves. In some places, algae clumped together with little bits of sand and soil to form mat-shaped structures called 'stomatolites'. Stromatolites couldn't do very much. They lived on rocks and waited as the tide came and went.

All the shell-animals are long gone. But there are still a few stomatolites left. There are some in Brazil and at Shark Bay in Western Australia. They are the oldest surviving living things on Earth. If only they could speak, they could probably answer our questions about what happened. But they can't, so we have to keep trying to work it out for ourselves.

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The earliest forms of life we know about emerged in the water. That's why we get so excited about whether there is water on other planets and moons, as it means there might be life there too. On Earth, life began to develop so long ago that we have divided up the time from then to now into big chunks called 'eras' and 'periods' to make sense of it all. Many of these chunks of time have names that are difficult to pronounce. Every so often, some-one changes their names or time they cover, which can be a bit confusing. So I've drawn up a chart summarising them all for you to follow.

Apart from the shell-animals and stomatolites, we have found remains of some other creatures from this early period. They include a creature called _Charnia_ , which was shaped a bit like a fern-leaf or large feather. It lived under water, where it was attached to rocks. No-one really knows how it worked as there none have survived for us to examine. The fossils of _Charnia_ and some other creatures from this time (which we call the 'Edicaran fauna') have been found near Wilpena Pound in South Australia. They look a bit like squashed prawns and limpets.

We don't know much about what happened over the next 45 to 50 million years. But about 530 million years ago, there seems to have been a sudden expansion in the number of living things. Sometimes, this period is called the 'Cambrian Explosion' as there was a sudden proliferation in life.

During this time, animals called trilobites emerged. Many of them looked like Balmain Bugs, having a segmented shell and eyes on little stalks. Trilobites became so well adapted to their environment that they were around for an extremely long time – about 270 million years. I have a fossilised tribolite, so you can see what they looked like.

By about 525 to 505 million years ago, we know there were quite a few different animals living in the oceans, as we've found their remains in Canada, Greenland and China. We call these creatures the 'Burgess fauna', as they were first discovered in the Burgess Mountains in Canada. They were certainly an odd-looking bunch. My favourite is one that had rows of sharp spines along their back and several pairs of legs. It is called _Hallucigenia_. For a long time, no-one was sure which way around it was supposed to stand. When it was first discovered, most people though it walked on the spines and that its pairs of legs were its mouths. But then they realised they'd been looking at it upside down and that _Hallucigenia_ probably used its spines to keep away predators.

We know there was one very dangerous animal that preyed on some of the others, an ugly-looking monster called _Anomalocaris_. It looked like a giant prawn and had a pair of arms covered in spikes near its mouth so it could shovel in any poor _Hallucigenias_ it happened to find.

The Burgess Fauna shows that, even at this early time, life was diverse. We are pretty lucky to know about them at all. Most of them had soft bodies that would have rotted away without a trace. The ones found in Canada, for example, lived in the ocean near the bottom of a mountain. Suddenly, one day there was a huge mudslide and they were buried before they could decay.

One the Burgess Fauna animals, which we call _Pikaia_ , had a very important feature – a backbone. This was something new in the animal world. It's important as we are descended from creatures that had backbones. _Pikaia_ is the first creature we have found that has a backbone. So maybe we have evolved from it ?

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At some point, we don't know when, an animal developed that could survive on land. So from this point, life evolved both in the oceans and on land. The land animals included two groups who later become very important to our story: the 'archosaurs' and the 'synapsids'.

About 250 million years ago, many animals suddenly became extinct. About 95 % of all ocean animals died out, along with about 70% of those living on land. This event is called It is called the 'Permian Extinction'. Its victims included the trilobites. No-one is really sure what happened. It may be that an asteroid hit Earth, killing everything it its wake. Or perhaps there was an increase in volcanic activity. Luckily, some of the archosaurs and synapsids survived. The archosaurs evolved into animals called 'dinosaurs', while the synapsids evolved into 'mammals'. Let's look at the dinosaurs first.

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For the next 160 million years, dinosaurs ruled Earth. There were quite a few different kinds. Many of them were very, very large. They've all been given strange names that none of them would ever have thought of themselves. Some were savage hunters and scavengers, like _Tyrannosaurus re_ x. Others were plant-eaters, like _Brontosaurus_ and _Stegosaurus_. They had some things in common though. They all had scaly skin like snakes and lizards. Plus they all laid eggs, just like birds do. In fact, believe it or not, birds are just small dinosaurs with feathers. They're not quite as big and impressive as _Brontosaurus_. But next time you see a Magpie family picking through the grass, you're looking at small dinosaurs looking for something to eat.

There were lots of other interesting animals around at this time. In the oceans, there were ammonites. They looked a bit like a cuttlefish and had beautiful shells shaped like ram's horns. They ranged in size from about that of our dining room table to a 5 cent coin. I have a small fossilised one you can look at. Two of the most striking included the _ichthyosaur_ , which looked a lot like a dolphin, and the _pterodactyl_ , a large flying reptile the size of a small plane. Both had jaws full of sharp teeth. Unfortunately, even sharp teeth were no guarantee of survival back then.

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Quite suddenly, about 65 million years ago, the dinosaurs and some other animals began to disappear. There are no dinosaurs left today, except for the birds. There are things that look like dinosaurs, like the Jacky Lizards that live near our place and New Zealand Tuatara. But they just look similar to dinosaurs, they are not closely related to them. All the ammonites were also wiped out.

Again, no-one is certain what happened. The most likely answer is that another asteroid hit the Earth. The main reason many people believe this is that if you dig down into the ground to reach the layers when the dinosaurs and ammonites started to vanish there is a thin layer of an element called iridium in the soil. Iridium is very rare on Earth. But it's very common in asteroids. So it seems a really big one hit. The explosion would have destroyed the forests and rivers for hundreds of kilometres around from where it fell.

The impact would have thrown up huge clouds of dust, blocking out the sunlight. Without sunlight, it is difficult for plants to grow: they can't make themselves any sugar. And if there are fewer plants, there's nothing for animals that eat them to live on. And then there's less plant-eaters for the meat-eaters to live on.

Whatever happened, two groups of animals survived. They included some small dinosaurs called 'theropods'. Some of them had feathers. Over time, they evolved into birds. Next time we have chicken for dinner, have a close look at the skins on its legs. It's covered in scales, just like those of its dinosaurs ancestors millions of years ago.

We have been very lucky to find the remains of some of these ancient birds. They include _Xiaotingia_ from China and _Archaeopteryx_ from Germany. They are very different from the birds we have now. _Archaeoptery_ x had little claws on its wings, which probably helped it climb around. Only one modern bird has something like this, the Hoatzin of South America. They are born with similar claws, but they lose them when they grow up. _Archaeoptery_ x also had a beak full of very sharp teeth. No modern birds have teeth.

_Xiaotingia_ and _Archaeopteryx_ show us how birds evolved from dinosaurs into the birds we have today. They are classic examples of types of animals we call 'transitional forms', as they demonstrate how one type of animal transitioned, or evolved, into another. These transitional forms are very important evidence of evolution.

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The other group that survived were the mammals. Before the dinosaurs died out, life was pretty hard for mammals as the meat-eating dinosaurs hunted them. So they had to hide in the trees and forests. Once the dinosaurs were gone, they could roam around more freely as they didn't have to worry as much about being eaten.

As there were fewer predators, a variety of large mammals evolved to fill the gap they left. They included huge woolly mammoths and mastodons, which looked like big hairy elephants, and sabre-toothed tigers. There were some really spectacular ones in Australia. They included giant wombats, called diprotodont, plus large echidnas and platypuses - much bigger than the ones we can see today. These large mammals are often collectively known as the 'megafauna' ('mega' means big and 'fauna' means animals).

A number of quite large birds also evolved. They included New Zealand's Moas, the tallest known birds, and the Elephant Bird of Madagascar, one of the heaviest known birds. There was also a large Australian bird called _Genyornis_ , which looked like a large emu.

There were also some creatures around that look nothing like anything we have now. The fossils of one of them have been found at St Peters, not far from Newtown, where I used to live. It was the _Labyrinthodont_ , an enormous amphibian that looked like a salamander.

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At the time _Labyrinthodont_ s roamed around St Peters, something else quite important was happening in our part of the world. About 130 million years ago, Gondwana, the super-continent that included New Zealand and Australia, began to split up.

The first bit to break off was the land that became Africa and South America. Soon after, it broke into two pieces, which is why the east coast of South America would fit together with the west coast of Africa if you tried to stick them back together. Ten million years later the part that became India broke off, leaving Australia, Antarctica and New Zealand still joined to together. Then, about 85 to 80 million years ago, New Zealand started moving away from Australia. Finally, about 80 million years ago, Australia and Antarctica spilt from each other.

That was the end of Gondwana. But it left us a remarkable legacy. Each time a piece of Gondwana split away, it saved some of the plants and animals that lived there at that time. New Zealand, for example, split off when large birds were dominant and there were very few mammals. So New Zealand became a land of birds. Apart from the Moas, they included the largest known eagle, the largest parrot, called the kakapo, and a very odd bird called a kiwi.

Kiwis are one of the oldest surviving types of birds. By 'oldest' I mean they have not changed, or evolved, much for a very long time. When New Zealand split off from Gondwana, it took some kiwis with it. Those left behind didn't survive as mammals evolved that ate them. But there were no mammals on New Zealand, except for two very small bats and seals and sea lions. These mammals do not eat kiwis, so kiwis survived in New Zealand and nowhere else. It was so safe for birds there that they didn't have to fly as they had no predators. As they didn't use their wings much, they got smaller and smaller. That's why the kiwi, the kakapo and many other New Zealand birds have tiny, useless wings or are weak fliers.

Apart from birds, New Zealand also has the last surviving population of an ancient kind of reptile called the 'tuatara'. They look a bit like big Jacky Lizards.

The same kind of thing happened to Australia. At the time large parts of Gondwana spilt away from it, the dominant mammals were large marsupials such as the diprotodon and monotremes such as the platypuses and echidnas. Some of these creatures had once been quite widespread in Gondwana. The fossils of large platypuses have, for example, been found in South America. But they only survived in Australia as they had no predators there.

So New Zealand and Australia became big floating museums of what Gondawa had been like at various times. Many of the animals found there are found nowhere else. This is why our unique plants and animals are so important to us and why we should protect them so you, Tom and your children can see them too.

Soon a new creature arrived that would change everything - us. Up until now, our history has been about nature. From this time, it will mostly be about people. Before we move on, let's have a look at nature as was when we arrived.

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Life on Earth is so interesting and diverse, it would take a life-time to describe it all in detail. So where to begin ? Let's start with where living things are found. They live in a wide variety of places. They include the polar ice-lands, oceans, coral reefs, coasts and rivers. Inland, there are marshes, mangrove swamps, reed-lands, rivers, forests, woodlands, heaths, grasslands and deserts. We call the places where things live their 'habitat'. So when we see the Magpies picking through our back lawn, we say our backyard, and probably many other backyards nearby, is their habitat. It is also out habitat as that's where our house is: we just share it.

There is life in the most inhospitable places. The deserts of Australia, Africa and the Americas support many plants and animals that have adapted to surviving the scorching days and freezing nights. Even in the deepest parts of the ocean, there is life. Actually, this is a pretty good place to start talking about life as, until recently, no-one thought there was anything there.

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One of deepest places on Earth is a rift near the Galapagos Islands off the coast of Ecuador in the Pacific Ocean. It is so deep that if you somehow managed to reach the bottom, the weight of the water on your body would crush you. So we can't live there. No-one thought anything could live there as it would be squashed by the water pressure. Then, to everyone's surprise, a little craft sent down to explore the rift found all sorts of animals down there. They included tubeworms, delicate animals that live in a tube-shaped shell they make for themselves from the compounds they excrete (just like the shell-animals and ammonites we looked at earlier).

How the tube-worms and others manage to survive was unclear. No sunlight reaches down that far. So plants can't live there as they have no light to make themselves any sugar. So everyone was wondering that if there are no plants down there, what are all these creatures eating ? Eventually, scientists realised they had a completely different source of food. The tube-worms were living near cracks in the Earth's crust at the bottom of the ocean. These cracks were letting out water and gases rich in elements, including carbon, heated by the Earth's magma. It turns out there were tiny bacteria living down there that could eat the carbon and other elements in this water. These bacteria were living either on or inside the tube-worms, allowing them to feed on it as well. So even though it's very dark down there and no-one was expecting to find them, the tube-worms and bacteria are thriving thanks to all the carbon-rich water and gases leaking out thorough these cracks.

If life can survive in such unfriendly places on Earth, maybe it also does on Mars. Or Europa ? Or Titan ? But we've found nothing there yet. So, for now, the only life we have to study is what's here on Earth.

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There are many other types of habitats and millions of different plants, animals and other things living in them. Even a drop of water from a creek or river will teem with many different creatures. If you look at it under the microscope, it may contain tiny hydra, worms, crustaceans, water bears, protozoa and algae.

No-one knows how many different things live on Earth. Early this year (2014), someone estimated that it was about 8,700,000 species. And they are just the ones we know about. New things are being discovered all the time. Not long ago, a new kind of tree kangaroo was found in Papua New Guinea and new type of primate was found in the Amazon Forest.

These things range from the enormous to the tiny. The largest living thing on earth is the Blue Whale. These whales are very rare. But sometimes, they swim past Sydney. So if we're lucky we might see one. The smallest things are tiny bacteria that you need a microscope to see. In between are many other extraordinary things. To help keep track of them all, we have put them into groups.

They include the mammals, which have live young fed on milk. Whales, dolphins, seals, elephants, lions, tigers, zebras, armadillos, pandas and cats are all mammals. They also include us and the animals related to us, such as gorillas, monkeys and lemurs.

Next come the marsupials, which are similar to mammals but their young are not completely developed when they are born. So they're kept in a pouch. Kangaroos and koalas are marsupials. So are possums and bandicoots that live in around our house. Then there are the monotremes, which are mammals that lay eggs. There are only two of them, the platypus and echidnas.

The next group are the birds. They range from large emus, cassowaries and bustards to tiny riflemen, pardalotes and hummingbirds. Then there are the reptiles. They include crocodiles, alligators, snakes, turtles, tortoises and the lizards, geckos and skinks that live in our backyard sometimes.

We also have some of the next group of creatures in our backyard, the amphibians. They include frogs, such as our Brown-striped Marsh Frogs, and salamanders, including the axolotl. Next, there are the fish. They include ocean fish, such as the Ocean Trout we often have for dinner, and the many colourful fish found on the Barrier Reef, like the Anemone Fish, the Parrot Fish - and the Red Bass that bit your toe. They also include the Seahorses. There are also fresh water fish such as the giant Murray Cod and Rainbow Trout. Then there are the crustaceans, such as crabs, scampi, prawns and Balmain Bugs.

There are also the molluscs, which have a shell. They include the oysters, mussels, limpets and all the little animals whose shells we find scattered along the beach. They also include the squids and octopuses, which propel themselves through the water by squirting out jets of water. Octopuses are very smart. If you give one a glass bottle with a prawn inside it, the octopus will work out how to take off the lid and get the prawn.

Jellyfish also propel themselves with jets of water. But they are not related to squids and octopus. They are in their own class of animals, which also includes anemones. Both jellyfish and anemones use their tentacles to sting their prey. But jellyfish can swim around freely, while anemones live on rocks and stay in the one place.

Then there are the arachnids, which include spiders, ticks and mites. We have quite a few different spiders living at our house. They include green spiders that live among the parsley, the Golden Orb Spiders than spin huge webs of yellow silk and cross-shaped spiders that throw little nets at their prey. Some spiders are so big that they catch small birds to eat. But they don't live near us, so there is no need to worry about them.

Then comes the largest group of all - the insects. There are millions of different kinds. We have over 50 different kinds at our house alone, ranging from dragonflies and stick insects (they look just like small twigs) to colourful butterflies, such as the Australian Admiral and Blue Triangle, cicadas and brightly-coloured ladybirds.

Next are all the plants, which range from huge kauri trees of New Zealand, Norfolk Island Pines and all different types of eucalypt trees near our house, such as the Blue Gums. They also include the brightly flowering shrubs and herbs we see in the local bush, such as the spider-flowers (grevilleas), Bacon and Eggs, Boronia, fuchsias, trigger plants and purple flags. In New Zealand, they include the beautiful kowhai and fuchsia trees. Some types of plants can live in very harsh environments. Cactuses and succulents, for example, can survive in the deserts as they have developed ways of retaining water.

Also, remember how we saw that plants need sunlight to survive ? There are some plants don't just live on sunlight. Sundews and pitcher plants, for example, have developed ways of catching insects for extra food. They attract them with sweet-smelling liquids, which insects love. The insects become trapped by the liquid and are dissolved into the plant.

Then come the fungi, which include the mushrooms we eat. Fungi come in a range of shapes and colours, including the golden cinnabar fungi, the red star fungi and small blue caps that look like tiny blue mushrooms. Some fungi even glow in the dark. Next are the mosses. The best place to see them is in the beech forests of southern New Zealand, where they cover parts of the forest floor like a bright green rug. Then there are the liverworts, which look a bit like mosses.

Last, but not least, are the lichens. Usually pale blue-green, orange or dark yellow in colour, they are the scaly growth often seen on rock or old statues. Although they don't look very interesting, lichens are a combination of a fungi and an algae. Fungi don't have any plants cells, so they can't use sunlight to feed themselves. It seems that, at some point, a fungus cell joined together with an algae so that it could do this.

So there it is - the short, short introduction to life on Earth. There are many different living things and many different habitats for them to live in. But most things can only survive in certain habitats. So some animals, such as cassowaries, can only live in the wet tropical rainforests as that is where they find the fruits and berries they live on. Others, such as otters, live in the sea or in rivers, as that is where they find the shell-fish they eat. If those animals lose their habitat, they have nowhere left to live and will become extinct.

This description is just the beginning. Life is like a big jigsaw puzzle – everything is, somehow or another, connected to everything else. And the reasons for this are very simple. All living things need the same things as us. They all need something to eat and somewhere to somewhere to live and raise their young. So it is important to understand how living things interact with their habitat and with each other. To help do this, naturalists have divided the Earth up into areas called 'bio-regions'.

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Bio-regions are distinctive collections of plants and animals only found in a particular place. The Earth has been divided up into about 30 bio-regions. It would take many books to describe them all, so we'll focus on Australia and New Zealand. Even this limited area is so rich in life that it has been divided up into four bio-regions: south-western Australia, central western Australia, north-eastern Australia and New Zealand, which forms a bio-region all by itself as it split off from Australia millions of years ago.

If you look closer at these four local bio-regions, they contain many different types of habitat. Australia, for example, has about 85 different types of habitat, ranging from stony plains and dunes to wet tropical rainforest. Our area, the Sydney Basin, is a separate bio-region all of its own. It contains many different types of habitat. Take Lindfield for example. Just up the road we have two different types of forests: sandstone-based eucalypt-angophora forest and shale-based blue gum high forest. Further up the road is Lane Cove River, where there are mudflats on which stands of casuarinas and mangroves grow.

Bio-regions are useful as a short-hand way of referring to the plants and animals found in a particular part of the world. But not many naturalists have enough time to study a whole bioregion. Instead, most focus on a particular habitat. Let's have a look at four local examples: (1) Agincourt Reef, which is part of the Great Barrier Reef, (2) Clovelly Beach in eastern Sydney, (3) the Wolli Creek Valley and (4) the Routeburn River and Ailsa Mountains in the Fiord Country of southern New Zealand.

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The oceans cover about three quarters of the Earth's surface. While we know little about them, they are extremely important to us. Firstly, they soak up huge amounts of carbon dioxide - a gas that would poison us if there was too much of it in the air. They also stabilise the Earth's temperature by soaking up much of the Sun's heat. The oceans circulate this heat though their currents, which cause many of the weather patterns we experience. If a current's temperature changes or it is blocked, it can change the weather. That, in turn, can alter our habitat - and not always in a good way.

In Gondwana times, northern Africa was once covered in jungles and lakes. Back then, the oceans could circulate around the globe freely, keeping them at a constant warm, temperature. But as the various parts of Gondwana broke away and banged together. This blocked the current around the Earth's poles from getting any warm water. So the temperature of the currents the circulated the poles dropped and the poles froze over. Also, the temperature of the current that passed north Africa heated up, drying out the top part of the continent.

So the Earth is a very delicate mechanism. Today, we are worried that people are making so much carbon dioxide that the oceans and atmosphere will not be able to absorb as much of the Sun's heat as it used to. This may affect the oceans' temperatures, disrupt their currents and cause global warming. The warmer weather may cause more storms, such as cyclones and hurricanes, and dry out the land used to grow food. It may also melt the polar ice caps, which will cool the oceans and interfere with their currents. If the oceans become too cool, it may spark another ice age.

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The best place to begin studying the sea is out on a reef. There are many reefs around the world. We are lucky, as we have one of the world's largest examples off the coast of Queensland. It's called the Great Barrier Reef, as it forms a barrier between the ocean and the coast. But even though reefs are quite big, they are made by tiny creatures called corals.

Corals only live in the ocean. They have a little shell around them made from a mineral called limestone. When the coral passes away, its shell sinks to the bottom of the ocean. In some places, over millions and millions of years, the little coral shells have accumulated until they form a reef. These reefs provide habitat and shelter to many different plants and animals. They are very delicate. If the Earth warms up too much, as many people expect, it will be too hot for many of the things that live on them to survive.

The Great Barrier Reef is so big that it would take a long time to see all of it. Some parts of it are very fragile, so people are not allowed to visit them in case they damage it. But in some places, you can go diving or snorkelling along parts of the reef and see all the amazing things that live there. They include the coral outcrops in the Agincourt Reef off the coast of Cairns in northern Queensland.

These outcrops are called 'bommies'. They are the tops of underwater mountains made mostly of coral. So when you swim around them, its as if you were swimming around a mountain peak. The first thing you notice is that the bommie is covered in many different types of coral, giant clams and anemones. Many coals are named after things they look like. So there is finger coral, which looks like fingers and brain coral, which looks like a human brain. Many of them are coloured in delicate shades of blue, green, purple and pink.

Living among the corals and anemones are many kinds of brightly coloured fish. There are the Parrot Fish, which are coloured bright green and crimson. They have large teeth, which they use to eat coral. You always know there are Parrot Fish nearby as you can hear the crunching noise they make as they eat. Then there are the Clown Fish, which live among the tentacles of the anemones. The anemones' tentacles can give a nasty sting. But as the Clown Fish are immune to them, they have learned to hide from predators by living among the tentacles.

There are many larger creatures around the reef. They include sea turtles. Every year, they come ashore ion the coral islands and dig burrows to lay their eggs in. The turtles then leave. After a while the eggs hatch and the baby turtles run for the ocean to start their life. Sadly, many are eaten by birds before they get there.

The largest creature of all is the Humped-backed Whale. Every winter, many hundreds of Hump-backs leave the oceans between southern Australia and Antarctica to spent summer in the north. If you go to Cape Solander at Botany Bay National Park, you can watch them swimming up the coast on their way there. When they come to the surface the breath, they give off a puff of water. Sometimes, they lunge out of the water and land on their backs with a big splash. No-one is sure why, although it seems like they are having a lot of fun !

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Other places to learn about the oceans are along the coast where they have washed sand up to form beaches. Clovelly Beach is in Sydney's eastern suburbs. Nana, Grandad and all of us lived there shortly after we came to Sydney. The beach itself is not very nice, as most of it has been covered in concrete. But it has two interesting features that let us see the kinds of things that live on the coast.

They include a small, narrow bay between the beach and the ocean. As it is quite sheltered and contains lots of nooks and crannies, many sea creatures live there. They include colourful fish such as the Senator Wrasse, which is green and crimson. The Damselfish, which is bright yellow and blue. There are also Pipefish, which are long and thin and Garfish, which have pointy noses. Most impressive of all are the Blue Gropers. They are large, friendly fish. The males are dark cobalt blue in colour and the females are green. Sometimes it's hard to tell whether the green ones are male or female as they are all born as females and some gradually turn into males. Often, when your snorkelling, the Gropers will come up to you as they're hoping to be fed. Sometimes I dive down to the bottom of the bay and lifts up some rocks for them so they can see if there is anything underneath to eat.

There is also a rock platform near the beach. At high tide, this platform is underwater. But at low tide, you can walk over it and see many of the creatures that live on the coastline. They include many different types of molluscs, such as limpets, periwinkles, and turban shells. They graze on the seaweed growing on the rocks, just like garden snails graze on the parsley in our backyard. The most impressive of them all is the Giant Black Sea Slug. It looks like an enormous snail.

In the rock pools, there are prickly sea urchins, starfish and small purple anemones with pink tentacles. Often the anemones keep their tentacles withdrawn. But if you are very patient, you might see one that has let them out so it can catch something to eat.

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Wolli Creek is south-west of Sydney. After living in Clovelly, we moved there as we got tired of living in a flat and wanted our own house. We liked the Valley so much we stayed there for many years.

Wolli Creek and most of the rest of Sydney sits on a big layer of sandstone. This sandstone was washed by enormous floods down from Antarctica to Sydney back in Gondwana times. You can see how strong those floods were at Undercliffe. In the side of the ridge, there is a S-shaped curl in the layers of sandstone, showing where the folds rushed over the earlier deposits and pulled them back on top of themselves. Over many millions of years, the Creek wore a valley through the sandstone between Kingsgrove and Undercliffe, from where it flows into the Cooks River.

Even though the Valley is quite small, it contains many different types of habitat. They range from mangroves, saltmarsh and reedlands to heathland, woodland and open forest. These habitats support many different kinds of native plants and animals, including mammals, birds, reptiles, frogs and insects. But each habitat only supports certain types of plants and animals.

First, there is the Creek itself. Mangroves grow in the muddy soil along its banks. Barnacles grown on the mangroves roots and small fiddler crabs live in burrows they dig into the mud. Several kinds of fish live in the Creek. Many of the Valley's birds depend on these animals for food. Darters, Egrets, and Herons patiently stand or sit by the Creek looking for a crab or fish to catch. Cormorants have a different approach: they chase fish through the water. Ducks 'dabble' in the Creek, often sticking their heads under water as far as they can reach to catch small fish and insects.

Behind the mangroves are the saltmarshes and reedbeds. They are covered in stands of short plants called samphire grass and tall, thin ones called _Phragmites_ reeds. The reed beds provide habitat for the Reed-Warblers, a migratory bird that comes of the Valley in the summer. They are also home to a tiny, brightly coloured bird called the Golden-headed Cisticloa, a tiny reed warbler that builds a ball-shaped nest among the reeds.

Beyond the saltmarsh and reedbeds are the grasslands. They provide habitat for Magpies, Mudlarks, Wagtails and Fairy-wrens, which hunt for insects amongst the grass. The next habitats are the heath and open forests. They are dominated by a variety of eucalypt and angophoras trees and smaller ones, such as bottlebrushes, paperbarks and tea trees. They also contain a number of plants with beautifully-coloured flowers, such as Native Fuchsia, Hardenbergia, Purple Flag and Trigger Plants.

This is the habitat for many different types of forest birds, including Eastern Yellow Robins, Spotted Pardalotes, Golden Whistlers, Yellow Thornbills, Black-faced Cuckoo-shrikes and honeyeaters, including Eastern Spinebills. Some of these birds live in the Valley all year around, while other migrate there during the autumn or summer. They include the Grey Fantail, Yellow-faced Honeyeater, Olive-backed Orioles, Spangled Drongo, Dollarbird, and Fairy Martin.

Sadly, there were once many other types of birds found in the Valley. They included Regent Honeyeaters, White-fronted Chats, Hooded Robins and Orange-winged Sitellas. Their habitat was the Valley's Ironbark-Turpentine forest. But as virtually all this type of forest in the Valley was cut down, these birds are now locally extinct.

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The Routeburn is a river that flows through the fiord country near Queenstown in southern New Zealand. Even though we lived nearby, I'd never done walked along the famous track that follows part of the River. It was Mummy's idea that we go walk it and we've spent many happy days there since.

The River is surrounded by a range of mountains. They are called the Ailsa Mountains and are part of New Zealand's South Alps. The Alps were created when the plate carrying New Zealand collided with the plate carrying Australia. It is a remote and beautiful place. If you fly into Dunedin on a clear day, the plane goes over the mountains and you can see row after row of huge icy peaks.

The Alps have created many river, but not all by themselves. Warm currents of air from Australia move east over the Tasman Sea. They hit the Alps, cool down and form clouds. The clouds burst, causing rain to rush down the sides of the Alps into the valleys below. This is how the Routeburn River began. Rain falls on the Ailsa Mountains, the water runs into the Routeburn Valley and the river runs through the Valley until it reaches Routeburn Falls.

Unlike the Wolli Creek Valley, the Routeburn Valley and surrounding landscape was not carved out by rivers and creeks. Instead, much of it was carved out by glaciers. Glaciers are what you get during an ice age. As the temperature drops, huge fields of ice accumulate. They grow bigger and bigger until they cover everything. As they spread out, they wear away the rocks underneath them, carving out valleys and passes. This is what happened in Fiordland.

If you go a bit further north we can see two glaciers that have survived from the last Ice Age, which only ended about 10,000 years ago. They are the Fox and Franz Joseph Glaciers on the west coast. Basically, they are valleys filled with ice.

There are many different vegetation communities along the Routeburn Valley. The main one are the Beech forests. Beech is an ancient type of tree that evolved while new Zealand was part of Gondwana. They have survived in New Zealand and a few other places. They grow very tall, so they make thick dark forests. They provide habitat for many of New Zealand's distinctive birds. They include the Kiwis, Bellbirds, Grey Warblers, Yellow-crown Parakeets, Keas, Kakas, Riflemen, Robins, Tomtits, Fantails and Rock Wrens.

Kiwis are nocturnal, meaning they only come out to look for food at night. We have never seen one in the wild, just in a zoo. But we have heard them calling out at night while staying in huts along the Routeburn Track. They have a loud, shrill call that sounds a bit like their name.

The Kea, Kaka and Yellow-crown Parakeets are all parrots. They are all from the same family of birds as the King Parrots that come to our house sometimes. But as they were isolated from the rest of the world for so long, many New Zealand birds have adapted differently from other birds. The Kea is a good example of this. It is the only parrot in the world that lives in an alpine habitat. It is also the only one that eats meat. They have a loud call, ' _kee-ya - kee-ya'_ , which is how they got their name. They are dark green and brown, with patches of bright orange under their wings. Keas are extremely clever and love paying games with one another. They can be a bit naughty sometimes. If you leave your boots outside, they will rip them apart.

The Bellbirds and Grey Warblers are renowned for their beautiful bell-like calls. The Robins, Tom-tits and Riflemen are all insect eaters. Robins and Fantails are very friendly and will follow you around so they can catch the insects you disturb. Riflemen are New Zealand's smallest bird. They spend the day looking flittering through the trees looking for insects on the leaves and bark. They have a very short tail. Rock Wrens are one of the most ancient types of songbird. They also have very short tails – so short that they look egg-shaped. They live among the rocks on the slopes of the mountains. To help them perch on the rocks, they have developed very big feet. But they are very rare and can only be seen in a few places now.

Sadly, other birds that were once very common here have disappeared. They include the Kakapo, the South Island Saddleback and the South Island Kokako.The Saddleback and Kokako are wattlebirds that are found only in New Zealand. They both have beautiful calls. The Kakapo is the world's largest parrot. Like the Kiwi, it only comes out at night. It is a deep green colour, which camouflages it in the dark forests. The males do something no other bird does. At night, they walk up to the top of a high point, where their voices will carry and dig a shallow basin in the ground which is called a 'lek'. They sit in the lek, take a deep breath and let out a soft, but penetrating booming noise. This is so they can attract female Kakapos.

When people arrived in New Zealand, they brought animals with them such as weasels, stoats and ferrets. They ate many of the Kakapos, Saddleback and Kokakos. Also many of the Kakapos were caught by the Māori and early settlers to eat, including, our famous ancestor, George Biggar. By the 1970s, there was only one Kakapo left in the whole of Fiordland. But lucky, some were found in Stewart Island. They are being taken care of and we hope that Kakapos will be brought back to the Fiordland again soon. But at the moment, they are very rare. We have only ever seen the stuffed ones kept in Museums.

There are no Saddlebacks or Kokakos left in Fiordland either. But luckily some survived in other parts of New Zealand. You can see them both at Tiritiri Matangi Island near Auckland. We've been there twice and have been lucky enough to see them there.

These are just a few of the many different kinds of habitats and bio-regions on Earth. As you grown up, we'll show you as many of them as we can. And when your old enough, we hope you will travel to some of the ones we have not been to so you can tell us what they are like.

**V. Us**

i

So what about us ? Where did people come from ? For many years, most people believed what Genesis said. It tells how God created the first man, called Adam, by scooping up some clay and breathing life into it. He realised Adam was probably lonely. So, while he was asleep, God took out one of Adam's ribs and made the first woman, Eve.

Even though this is a Bible story, there must have been some sort of Adam and Eve or none of us would be here. As we're all human, we must have had a common ancestor back in time. We have found fossils of some of the earlier types of people. They show that our distant ancestors looked much like large primates, such as gorillas and apes. They have all been found in Africa. So maybe Adam and Eve came from there ?

Africa is now a very dry place. Much of it is desert and savannah. But a long time ago, it was covered with forests and grasslands. Up in the trees lived various kinds of primates, which is the name we use for the group of animals we come from. They lived in family groups. During the day they came down from the trees, looked for food, cared for their young and squabbled over things - much like people still do today. At night, they climbed back into the trees and slept up in the branches.

Gradually, the weather began to change. Africa became drier and it became harder for the primates to find food. So they began to spend more and more time on the ground. This was a bit dangerous. If you're up in the trees, it's harder for predator to grab you. But if you're down on the ground, you're more exposed. So as they weren't as safe on the ground as they had been up in the trees, the primate had to learn new skills to survive. Also, as there was less to eat, the primates had to find new types of food. So in addition to collecting nuts and berries, they had to learn how to catch things. So they became both hunters and the hunted.

This is a difficult situation. It puts a lot of pressure on an animal, forcing it to learn to protect itself and to find food at the same time. But primates are intelligent creatures – they remember things and can reason their way through problems, and so learn new skills. The primates responded by developing two skills. They got better at communicating with each other so they could plan how to get food and keep safe. They also began to make tools.

The ability to communicate is not unique to humans. All animals communicate in some way. Whales and dolphins call under water, birds 'sing' and dogs bark. Julia and Lily communicate with us all the time, especially when they're hungry. They call out to be fed every morning. Lily cries out when she wants someone to play 'fetch' with her. Sometimes, they growl at each other. But eventually, primates would develop their ability to communicate to do something other animals cannot: to permanently record information so it could be recalled later.

There is a famous scene in a movie called _2001: A Space Odyssey_ , where two groups of primates live near one another in the savannah. There is a pond there, which seems to be the only water available, so they're always fighting over it. One day, one of the primates picks up an old bone and uses to hit things. The primate realises this can be used as a weapon. The next time there is a fight over the pond, he uses it to kill one of the primate from the other tribe so that his people can drink from it.

Maybe something like this did happen and all the other primates would have learned to do the same thing. It would have made a big difference to their lives. They could make tools to hunt food and protect themselves. Eventually, one primate must have worked out that you could make sharp, durable tools by chipping pieces off certain types of rocks. These are the first hand-made tools left behind by the primates that we have found. These skills indicate new kinds of primate had evolved. We call them 'hominids', which means 'man-like'.

The stones hominids used to make some of these tools showed that different groups of them were trading with one another. There is, for example, a type of stone called obsidian. It's a glassy stone made by volcanoes – I have a piece from northern Queensland I can show you. As the flakes that split from it are extremely sharp, it was prized for making tools. Obsidian must have been quite valuable as pieces of it have been found far away from where it originated.

ii

For millions of years, many kinds of hominids lived in Africa. At one point, there were seven or eight different types living at the same time. We've given them names so we can keep track of them all. Every few years, a new kind is discovered. As I was writing this (September 2011), the discovery of yet another one has been announced. So we may be alone in the Universe. But, at one time at least, not on our planet. These things change so quickly this will probably be out of date before you read it.

The first hominid that seems to be related to us is known as _Australopithecus_. They were quite short and looked like big monkeys, except they could walk more upright. Then came one that looked a little bit more like us called _Homo habilus_ , which means 'Handy Man', as he was good at making tools. Then came _Homo erecuts_ , which means 'Upright Man'. They were the first who was able to stand up straight.

_Homo erectus_ was the first traveller. About 1.8 million years ago, some of them left Africa. No-one is certain why they left. It may have been as there wasn't enough food for them there. It may have been there was too much competition with the other hominids. Maybe they were just curious. It may have been all these things. Whatever it was, they travelled as far as China and Java, where their remains have been found.

After a while, other groups of hominids decided to leave Africa too. They included _Homo heidlebergenisis_ , which left about 800,000 years ago. Then some left who were very similar to us, except they were noticeably larger. We don't know what they called themselves. But we call them the 'Neanderthals', as their remains were first found in the Neanderthal Valley in Germany. These were the bones I mentioned earlier – the ones that got people thinking about whether Genesis was true or not.

The Neanderthals lived in family groups, made their own clothes, tools and jewellery. They were able to survive harsh winters and spread throughout much of Europe. The second group were very small: we call them _Homo floresiensis_ , as they were first found on the island of Flores in Indonesia.

Finally, we came along, emerging in Africa only about 200,000 years ago. While we dominate the planet, it is important to remember we are just another animal. We even have a name: _Home sapiens_ , which means 'thinking man'. It seems a silly name to give us. Obviously, all the other hominids were thinking too, or they wouldn't have lasted very long. Plus sometimes it pretty clear we don't really think that much at all.

_Homo sapiens_ left Africa too, about 125,000 years ago. They must have met up with the _Homo erectus_ people and the Neanderthals in some places. No-one is sure if they got on together. As all three competed from the same land and food, it may not have worked out very well. It seems the _Homo sapiens_ and Neanderthals tried to have families together, as many people from Europe have some Neanderthals genes. But it's likely we killed them all, and not that long ago either. The last Neanderthals lived on the island of Gibraltar only 24,000 years ago. The little _Homo floresiensis_ people survived on Flor until about 12,000 years ago. So now all the _Homo erectus,_ Neanderthals and _Homo floresiensis_ people are gone, leaving just us.

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As with so many other things, no-one is sure if this is what actually happened. Whether three separate waves of hominids - _Homo erectus,_ Neanderthals and _Homo sapiens_ \- left Africa at various times is not certain. It may be that they are all descended from _Homo erectus_. In other words, it may be that the Neanderthals and _Homo sapiens_ evolved from _Homo erectus_ in the various places where _Homo erectus_ migrated to. So instead of everything coming from 'out of Africa', it may be that the Neanderthals, _Homo floresiensis_ and _Homo sapiens_ evolved locally in various places from a hominid that had already left Africa instead of coming from Africa themselves.

We are learning more about this thanks to 'geneticists', the scientists who study genes. They have been able to extract some genetic material from the remains of these early hominids. This helps us track them back to where they came from and to tell how they are related. So I'm sure we'll have more news on this soon.

iv

As you can see, we don't know as much as we'd like to about our early history. The first humans didn't leave us any records as no-one could write. They didn't leave us any books, diaries or newspapers recording what they got up to. People only started making written records about 4000 years ago, which is not that long ago considering how many thousands of years we've been around. Before then, all we have are bits and pieces of their skeletons, their tools, art work and their buildings to indicate how they lived.

We have some idea of what happened since we turned up. We are able to work out what conditions we like on Earth by studying bubbles of gas trapped in the layers of ice that have accumulated over Antarctica. The gases found in those bubbles indicate what the temperature was like when they formed. We are also able to work out where various groups of people came from by studying their genes. We can work out something about how these people lived by digging up the places they lived in and where they were buried. The scientists who find and study this material are called 'palaeontologists' and 'archaeologists'. We can date some of these things by measuring the amounts of certain chemicals in them as those chemicals decay at a fixed rate.

v

After leaving Africa, groups of people began to settle down in particular areas. This all happened over such a long time that it has been divided it up into periods with odd-sounding names, just like the geological history of the Earth. We've also given each group of people its own name so everyone will know which one we're talking about.

All the time from when people first made tools, about 2,600,000 years ago to about 4500 BC is divided up into three periods: the Palaeolithic (which means the 'Old Stone Age'), the Mesolithic (the 'Middle Stone Age') and the Neolithic (the 'New Stone Age'). All the time from 4500 BC up to now is divided up into 5 ages: the Copper Age, Bronze Age, Iron Age, Middle Ages and the Modern Age - which is the age we're in now.

Some of these ages got their names from the material people used to make things with. Christian Thomsen, a Danish museum curator, noticed that at as people developed their technological skills over time, the materials to make tools and weapons became more sophisticated. During the earliest period, the Stone Age, people only used stone to make tools. Then some people learned how to use copper, which can be made into a wider range of tools and weapons than stone as it is more flexible. Then people learned to mix copper with tin to make bronze, which is harder than copper. And lastly they began to use iron, which is harder than copper or bronze.

These ages have been divided up into lots of shorter periods. They are often defined by the communities that lived at certain places at a particular time. Often, all that is left of these communities is their tools, pottery, graves and art work.

Usually, each community made a distinctive version of some of these things. So when we find, for example, a particular kind of pottery made by 'People A' in a particular area settled by 'People B', it is likely that People A were living there at some time or trading with them. We call these collections of people and their pottery a 'culture'. The stone tools made by the Neanderthals, for example, are part of four cultures: the Mousterian, Châtelperronian, Gravettian and Aurignacian. The tools made by _Homo sapiens_ are part of the Aurignacian culture.

These differences are also reflected in the art work each community made. Art is another of those things said to distinguish us from other animals. But it is not unique to us. Other animals like decorating. Male bowerbirds, for example, collect shells, berries and feathers to decorate the bowers they use to attract a mate. The Greater Bowerbirds in northern Queensland use snail shells to decorate theirs. Satin Bowerbirds in Sydney use Sulphur-crested Cockatoo crest feathers and blue drinking straws.

But humans are distinct in that they make representations of things. Why they started doing this is unknown. Some of the earliest human art work is found in caves in France, which were decorated in Palaeolithic times. One famous example, at Lascaux near Montignac, features paintings and engravings of wild bulls, bison, horses and deer. These paintings may have been made to encourage the gods to make sure there was plenty of game around to hunt. Or they may have been painted to teach the young ones the different kinds of animals and how to hunt them.

Some communities develop a more complex type of culture, which we call 'civilisation.' When does a culture become a civilisation ? How did humans come to develop it ?

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People have to be able to survive wherever they're living. If you live in the desert, you need to make sure you can survive the hot days and freezing nights. If you live near the North Pole, you have to be able to survive the intense cold. So different cultures and groups within cultures, which we call 'societies', develop in different ways. They all have their own way of organising themselves so that they have enough food and shelter to survive. As they learn how to do this, societies and cultures develop their own beliefs about the world around them and opinions on how people should live their lives. This information is passed down from one generation to the next. As people did not write until recently, this information was passed down in the form of stories, myths and legends as they are easier to remember.

Incidentally, it's not just humans who do this. Gorillas, meerkats, bees, ants and termites all have highly organised societies. They live in family groups, help each other find food and protect each other. Bees, ants and termites build impressive structures to live in. Some kinds of termites build their mounds in such a way so the Sun warms them on one side when it rises and on the other while it sets. They also make sure their mounds are well ventilated so they don't get too hot and well insulated so they don't get too cold. They can pass on information to each other. When bees arrive back at the hive, they do a dance to show the other bees where there's lots of pollen to collect.

What makes humans different from these other animals ? The most common answer is that we have learned to control their environment. Over thousands of years, we have learned to grow crops, dam rivers and domesticate animals such as cattle, sheep and goats. But we are not alone in being able to do some of these things. Leaf-cutter Ants grow crops of fungus. Beavers build large dams to create ponds for their families live in. Sugar Ants have worked out they can get sugar from small insects called Aphids. They take great care to protect the Aphids from predators, such as Ladybirds, and help them find food. The Ants even let the Aphids live in their nest during the winter: although they drug them and rip their little wings off to stop them flying away.

It is a question of scale. We are bigger than ants, so can have a bigger impact on the environment. The things we do are more complex. The Ants keep Aphids for the same reason we keep cows and sheep. But we have changed those animals by only breeding the ones that have feature we like, such as a capacity to produce lots of milk and to grow fat and provide more meat. We call this 'artificial selection'. It is practically the same as 'natural selection', except that we are the selectors, not the environment. So it is probably fair to say we are different because of the scale and complexity of what we can do.

Accounts human history, from this point, often become divorced from natural history. They focus almost exclusively on the development of cultures and civilisations and their conflicts with each another. Their relationships with nature are often ignored – as if they were living in a vacuum. But it is often difficult to make a clean break between human and natural history, so I will try to cover both.

vii

Survival is a precarious business. Imagine if you had to catch all your meals. What if you couldn't catch a fish or find any birds' eggs to eat. You would have to go hungry. If a culture is to develop into a civilisation, survival itself is not enough. It needs to develop to a point beyond this so that it can feed and protect all its members. Also, a society can grow so large that not everyone knows everyone else. So it needs to form some sort of identity to stay united.

As no-one agrees on what makes a civilisation, the best place to start is back at the beginning. First, everyone needs to be fed. That can mean making huge changes to the environment. If the land is dry, it needs to be irrigated. This can mean building ditches and canals. If the rivers tend to flood too often, they need to be kept in with levee banks. So you need large numbers of people to work together to build these things. But why would people do this ? What's to stop them running away to somewhere else where they don't have to work so hard ? The incentive is survival. Even if they ran away, they'd still have to find their own food and that is often not easy. So people surrender some of their freedom and work together to do things that will benefit them and everyone else in the community.

Second, everyone needs shelter. But if some people are working building dams and bridges, they are not going to have time to build themselves a house. So someone else will have to help them. When this happens in a society, it creates what is called a 'division of labour'. In other words, some members of a society have particular jobs that they do. It may be growing crops or forging metal tools. Whatever that job is, it has some value to everyone and so is a contribution to the community as a whole.

Now if you have a division of labour and are well organised, you can grow more grain or raise more cattle that everyone needs to survive. This means you have spare food you can eat later. Humans are not the only ones who do this. Squirrels and woodpeckers store acorns so they have enough food to get though the winter. But once again it's a matter of scale: humans can do it to a greater extent. It can be to such a great extent that not everyone needs to work all the time. They have leisure to do other things.

When people have leisure, they can realise their creative potential. People have time to tell stories, develop arts, such as making jewellery, and reflect on the nature of the world and their place in it. They may become anxious to record what they have learned and develop writing.

If a culture has gotten to this point, it is likely the people have confidence in the future. In other words, they believe their hard work is not for nothing and that if they push on they can continue to make their lives better in some way. It is when a culture reaches this level of comfort and inspiration then you probably have a civilisation.

viii

Well, that's what a lot of people used to think anyway. A recent discovery in Turkey shows that you do not need to have agriculture to start a civilisation. At Göbeki Tepe, there are a number of complex structures that look a lot like temples. They were created by a highly developed culture. But it seems those people did not grow any crops and were hunter-gatherers instead. These temples are very old – they were built between 12,000 and 10,000 years ago. So some groups of people must have been more advanced longer ago than we expected.

Advanced cultures soon established themselves in some places. One particularly fascinating example is the settlement of Çatalhöyük in Turkey. It was first occupied about 2000 years after Göbeki Tepe. Sadly, its people had no writing, so we don't have any first-hand information from them about their culture. But the archaeologists who excavated the site have made some very interesting discoveries. Unlike Göbeki Tepe, Çatalhöyük was an urban settlement. Its people supported themselves by growing crops and raising cattle. They lived in small mud-brick houses which they occasionally decorated with wall paintings. One of these paintings is a bird's eye view of the town itself, showing rows of little houses. It also shows the local volcano in the background – it seems to be erupting.

The people also built other structures that seem to be temples. They appear to have worshipped a goddess, but we don't know her name. They fed their dead to the vultures, just like some Tibetans and Zoroastrians in Indian still do. We know this as the wall paintings on one of their buildings shows bodies being fed to vultures. The Çatalhöyük people probably thought that as vultures can fly, they took the soul of the dead people they ate to heaven. Since they didn't leave us any written records, this is just a guess.

Vultures, incidentally, are very useful to have around as they eat things that would otherwise be left to rot in the street. This stops disease from spreading. Feeding them the dead is quite a neat and tidy way of getting rid of corpses. There's no body that has to be buried or cremated and the vultures get a meal for all their hard work.

ix

Many cultures show that you don't need writing to be successful. They include the people who settled in Britain. Even though it is far away from Africa, people have lived there for a very long time.

The first ones arrived about 700,000 years ago. At this time, Britain and Europe were linked by a land bridge. The Thames and Seine were tributaries of a large river that ran where the English Channel is now. These early people left no records, except the bones and flint tools, which have been found at Happisburg and Pakefield.

About 500,000 years ago, new people arrived. They seem to have been _Homo heidelbergensis_ , one of the many early types of hominid. Their remains have been found at Boxgrove, and include Acheulean axes and the bones of the hippopotamuses, rhinoceroses and elephants they had hunted.

Then there was an ice age, which seems to have driven everyone out of Britain. They didn't come back until about 424,000 years ago. Then there was another ice age, which lasted from about 352,000 to 130,000 years ago. It was followed by another, final ice age that started about 70,000 years ago. Although it was cold, herds of mammoths, deer, horses and rhinoceroses managed to survive. This probably explains how the Neanderthals, who arrived about 40,000 years ago, were able to survive. About 10,000 years later, _Homo sapiens_ turned up. The earliest human remains were found at Paviland.

About 22,000 years ago, the weather got even colder – so cold it may have forced everyone out of Britain again. They, and the animals they hunted, were back 8000 years later. Their remains have been found at Gough's Cave. They include flint tools and ornaments made out of shells, amber, antlers and mammoth ivory. The bones of horses, deer, hyenas and hares were also found.

By about 7500 BC, rising sea levels had cut Britain off from Ireland. About 1000 years later, it was cut off from Europe. The weather became warmer, which affected the types of plants that grew. Until then, Britain had been covered by open plans. But as it warmed up, forests started to grow. This didn't suit the mammoths, who were plains animals, and they gradually disappeared. Other animals, such as deer, boar and aurochs, became more difficult to catch. So people had to develop new hunting techniques.

At about this time, the local people developed agriculture. They began farming cereals and domesticating animals, such as cattle, sheep, pigs and goats. Whether they worked it out themselves or another culture arrived from Europe and introduced it is unknown. They began putting up permanent structures, such as large earthworks called 'barrows.' They also built some of the first known stone buildings. Some of these survive at Maseshowe, the Bay of Skaill ('Skara Brae'), Stenness and Brodgar in the Orkney Islands.

About 4800 years ago, the people at Maseshowe built a huge stone building to bury their dead in. At Bay of Skaill, sometime between 5180 and 4500 years ago, the locals built a small village of stone houses – complete with stone dressing tables and cupboards to store things in. Those at Stenne built a monument consisting of rings of stone pillars, known today as the 'Standing Stones of Stenness'. There is another one at Brodgar, known as the 'Ring of Brodgar'. They may have been large sundials to mark the passing seasons. There are other famous stone circles on the mainland at Avesbury and Stonehenge in Wiltshire.

Even though they had no writing, these were sophisticated societies. They make you wonder what you really need to have a 'civilisation'.

x

The first cultures which most historians agree were 'civilisations' developed near rivers. The first one arose between the Tigris and Euphrates, about seven thousand years ago, in Iraq. Its people are known as the Sumerians. Shortly afterwards, another one emerged along the banks of the River Nile in Egypt. Civilisations also emerged on the island of Crete of the Aegean Sea and in the east, along the Yellow River in China and the Indus River in India and Pakistan. They were not isolated from one another. There was trade between the Sumerians, Egyptians and Crete. There was contact between China and India. But there was little contact between the west and east.

xi

The Bible mentions Sumer, just after the story of Noah and the Ark. But it's not called Sumer there, it's called the land of Shi'-när. It's where Noah's descendants lived after the Flood. It seems the first people to settle there arrived about 6500 years ago. We call them to Ubaidians. As with some many other cultures, we don't know what they called themselves, so we've made up a name for them. When they moved in they drained the marshes that grew along the rivers, started growing crops, making pottery and metal goods and trading with other cultures nearby.

About 2000 years later, the Sumerians moved in. They built large cities at Eridu, Ur, Uruk and Lagash out of mud brick and built irrigation systems so they could grow more crops. They were very religious and had numerous gods. They built special buildings, called 'temples', where they worshipped them. These temples included tall, step-shaped buildings called 'ziggurats'. It seems the Sumerians believed that if they stood on the top of a tall building, they would be closer to their gods.

The temples were run by men called 'priests'. They were responsible for keeping the gods happy by making offerings to them and keeping their temps in good repair. One of the priests acted as the king. Over time, the priests and the king grew rich and powerful and so came to rule over all the others.

As far as we know, the Sumerians were the first people who had writing. They kept their records by using clay tablets. They'd get some clay, flatten it out to make 'tablets' and press their letters onto it using a piece of reed. As the letters were wedge-shaped, it's called 'cuneiform' writing. Thousands of years later, archaeologists found some of their tablets amidst the ruins of their cities.

These tablets preserve details of their history and culture. Remember the story of Noah and the Ark ? A lot of people think that actually happened in Sumer. The Sumerians had a story about a king of Uruk called Gilgamesh. It includes an account of how the gods planned to flood the Tigris and Euphrates, covering all the land between them in water. The gods were supposed to keep this a secret. But one of the Ea, told a man called Utnapishtim. He built a large boat and managed to survive. It seems that whoever wrote the Bible many have heard this story and decided to use it in the Book of Genesis.

Sumerian civilisation lasted for many centuries. When their mud-brick buildings crumbled, the Sumerians simply levelled off the ground and built on top of the old structures. As they rebuilt their homes and temples over the centuries, the ground level slowly rose higher and higher, until their cities were sitting on hills, known as 'tells', that we can still see today.

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The idea of building temples and writing things down spread from Sumer to a new civilisation emerging along the banks of the River Nile in north-east Africa: Egypt.

The famous Greek historian Herodotus said " _Egypt is the gift of the Nile_ ". It begins in the south, near the mountains of Ethiopia. Heavy rains flow from the mountains into a local river, the Blue Nile. As it flows north through Sudan, its waters merge with those of another river, the White Nile, near the city of Khartoum. The Nile flows north until it reaches Cairo. There, it fans out into several smaller rivers which flow out into the Mediterranean Sea. One of these smaller rivers flows past the city of Alexandria, which is where Pappie came from.

Do you remember how we talked about the time Africa was covered with forests and grasslands ? This lasted until about 9000 years ago. Then, the Sahara Desert was savannah country, with lakes and herds of wildlife, such as giraffes. We know this because the people who lived there decorated the caves they lived in with paintings of themselves and the animals they hunted. The Sahara is now a desert, but these paintings are still there.

As the land dried out, the people living there needed to move somewhere with water. So they began to move to the Nile and settled along its banks. This turned out to be a great idea. Each year, the Nile would flood, carrying loads of fertile silt from the south. The Nile deposited this silt on its banks and the Egyptians used to grow their crops. As the silt was so rich, they were able to grow plenty of grain. So that is why we say Egypt was the gift of the Nile.

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For a long time, various different groups lived along the River. The ones who lived in the north, Upper Egypt, were called the 'Papyrus People', after a plant that grew in abundance along the River. The ones in the south, Lower Egypt, did not have a special name. But they had a leader, Narmer.

Narmer wasn't happy just ruling the south. He wanted to rule all of Egypt. By this time, there was a lot of trade between Sumer and the Egyptians. It was quite lucrative and it seems Narmer wanted to control it so he could make more money. So he set out to conquer the lands along the entire length of the Nile.

Narmer defeated the Papyrus People and united Egypt into one kingdom. He had a plaque carved showing him wearing the crown of southern Egypt (also called, confusingly, 'Upper Egypt') on one side and wearing the crown of northern Egypt (also called 'Lower Egypt') on the other. The kingdom Narmer set up would survive for almost three thousand years – a very long time when you think that Australia was only united about 114 years ago.

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The Egyptians had many gods. They included Nut, the Sky God. The Egyptians believed the Sun rose each morning when Nut gave birth to it and set in the evening when she ate it. You can see Nut with the Sun travelling through her body on the beautiful papyrus painting Mummy brought back from her travels in Egypt. They had many other gods. They included Osiris, who was a famous king, his wife, Isis. Then there was Seth, who killed Osiris and chopped him up into little pieces. Then Isis put him back together again. There was Toth the Ibis god, who was very wise. And there was Horus, the falcon god.

The Egyptians copied the Sumerians and built temples to their gods. It seems they also got the ideas for some of their architecture and artwork from them too - many early Egyptian buildings and artworks feature Sumerian designs.

Today, we usually remember the Egyptians for their funerary rites. They believed people had 'souls' and that when they died, their souls went to the afterlife and live happily forever with the gods and all the other souls. But the Egyptians also believed this only happened if a person's body was preserved after they died. So they developed an elaborate way of preserving them. This involved drying them out with salt, covering them with unguents so they did not smell too much and then wrapping them in layers of linen bandages. We call these wrapped-up bodies 'mummies'. The method worked quite well sometimes. We have found the mummies of some famous pharaohs, which is what the Egyptians called their kings, and can see just what they looked like.

The next step was to store the mummy so that it would be safe forever. The pharaohs and other wealthy Egyptians took great trouble to build large tombs for their mummies. Over time, the tombs got more and more elaborate. Narmer was built in a simply brick-lined pit. Later pharaohs had large, bench-shaped structures called 'mastabas' built to house their mummy ('mastaba' is from the Arabic for mud bench).

When Djoser became pharaoh, he wanted something more impressive. Imhotep, his architect, hit on the idea of building six mastabas one on top of each other - like a pile of boxes, which a large box at the bottom, a smaller on top of that, then a smaller one and so on. Djoser's tomb still stand sat Saqqara: it is called the Step Pyramid, as the sis mastabas piled up on top of each other look a bit like steps.

A bit later, the Pharaoh Snefru decided he wanted a pyramid with smooth sides, instead of step-shaped ones. It took his builders three attempts to get it right. Their first attempt, at Meidum, failed as the sides were too steep and it collapsed. Their second attempt at Dashur, also had problems. This time the sides were also too steep – but they didn't realise until they were more than half finished. So they had to build the rest at a shallower angle, giving the pyramid a bent look. We still call it the Bent Pyramid. Snefru must have been very annoyed with his builders. They were lucky the third time and built him a perfect pyramid, which is also at Dashur and is known as the 'Red Pyramid'.

While you can still see all of Snefru's pyramids today, the most famous of all the pyramids are those at Giza, near Cairo. They were built by the Pharaohs Khufu (also known as 'Cheops'), his son, Khafre ('Chephren') and Menkaure ('Mycerinus'). The pyramid of Khufu is the largest of them all and is known as the Great Pyramid. The Giza pyramids are guarded by an enormous statue of a lion with a man's head and an enigmatic smile. It's called the Sphinx.

Although the Egyptians were obsessed with death, they were usually very happy people who enjoyed having parties. They often decorated their tombs with paintings showing what a good time they were having.

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Nothing lasts forever, not even a civilisation. Eventually both Sumer and Egypt collapsed. In about 2185 BC, the kingdom Narmer established fell apart for a while due to weak rulers and famine. About 35 years later, the Sumerians were conquered by a less-developed people called the Gutians. But while civilisations may not be permanent, many of them have the ability to adapt to changing circumstances and renew themselves.

Before long, a series of strong leaders reunited Egypt and it experienced peace and prosperity again. But the Sumerians were not so lucky. They briefly recovered control of their lands, only to be conquered again by the Amorites and Babylonians. They held Sumer until they, in turn, were conquered by the Hittites in 1595 BC. The Hittites came from Turkey. We'll come back to them shortly.

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In the meantime, a new civilisation had emerged on the Island of Crete in the Aegean Sea. They were the Minoans, although as we can't read their writing we don't know what called themselves. It seems the Minoans came from Anatolia, which is another name for Turkey.

By about 2700 BC the Minoans had developed a fascinating culture. They built large palaces for their kings at various places, including Knossos and Mallia. They worshipped a Snake Goddess and a Poppy Goddess whose real names we don't know. They had unusual religious rites, which included jumping over bulls. They made beautiful works of art that showed a great love of nature. Their houses, their jewellery, jugs and pots were richly decorated with dolphins, octopuses, nautilus shells, swallows and monkeys. When I first met Mummy at Law School, she was wearing a silver copy of a beautiful Minoan pendant found at the Palace at Mallia. It shows two bees or wasps standing together holding up a piece of honeycomb. Years, later, when we visited Crete, I bought Mummy a gold copy of the pendant as an engagement present, instead of a boring old ring.

The Minoans were great traders. They took their pottery, saffron and tin, which was used to make bronze, to Greece, Egypt, Mesopotamia and Anatolia. There is a famous Egyptian painting in the tomb of Senenmut at Thebes that shows some Minoans carrying their distinctive pots. They had a system of writing, but no-one can read it yet.

The Minoans seem to have been happy people. Women and men were treated equally and both took great care in their appearance. They did not live just on Crete. They also lived on the beautiful island of Santorini nearby. Unfortunately, Santorini has a very large volcano called Thera. In about 1450 BC, Thera exploded, taking a huge chunk out of the middle of Santorini and almost destroying the Minoan society. The crater left by the explosion is still there. You can stay in the village of Oia, which is perched on the edge of the crater, look out across the Aegean and wonder about how fragile civilisations are.

Many of the palaces, including the one at Mallia, were also destroyed. Then, just as the Minoans were getting back on their feet, they were invaded by a less sophisticated people, the Mycenaeans. They were Indo-Europeans who came from Greece sometime between 1420 and 1375 BC.

Mummy and I have been to their famous city, Mycenae, in Greece. But it's quite small and, except for the statues of some lions above the city gates and large tombs, there's not much to see. Knossos is much more impressive. The Mycenaean adopted the Minoan writing system and used clay tablets, like the Sumerians, to keep their records. Their script is the earliest form of Greek, which we call 'Linear B'. Some of their tablets have survived. But they are just inventories of weapons and supplies.

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The Mycenaeans were not happy with just conquering the Minoans. They wanted to control the whole Aegean. They had only one rival – the ancient city of Troy, which lay on the west coast of Anatolia. What happened is this. Hector, son of the Trojan king Priam, somehow ended up with Helen, wife of the king of Sparta, Menelaus. No-one knows how they ended up together. But the Mycenaean kings were very unhappy about the affair and invaded Troy.

After many years of battle, they were unable to take the city. Then Ulysses, one of the Mycenaean kings, had an idea. They would pretend to give up and sail back to Greece – leaving behind a giant horse as a tribute to the Trojans. The giant horse was built and the Mycenaeans pretended to sail home. But hidden inside the horse were some Mycenaeans soldiers.

The Trojans saw the horse and dragged it inside the city walls. When night fell, the Mycenaeans climbed out of the horse, flung open the city gates and let all the other Mycenaeans in. They destroyed Troy and killed most of the Trojans, including Hector and Priam. So that is why we still say beware of Greek bearing gifts !

The story of the Trojan War was so famous that it was preserved by word-of-mouth for many hundreds of years. It was eventually written down and is one of the first surviving works of western literature. We still read it now, almost 3200 years later. You can also visit the site of Troy, although there isn't much to see there now.

Things didn't really work out for the Mycenaeans. In about 1100 BC, their lands were invaded by the Dorians, a culture from northern Greece that ultimately took control of the Aegean. They built a whole new civilisation that, in some ways, is still with us today. But that was in the future. For the next three to four hundred years, there wasn't much happening in Greece. Sometimes, this period is called the 'Dark Age', other times it is called the 'Geometric Period', as during this time the Greeks decorated much of their pottery with geometric patterns. But there was plenty going on elsewhere.

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While the Minoans, Mycenaeans and Greeks came and went in the Aegean, societies had grown up along the Yellow River in China. The Chinese say their first rulers were 'three sovereigns and five emperors' of great wisdom and learning who taught them about making fire, farming, manufacturing silk, medicine, how to arrange their calendar and how to write.

After them came the Xia Dynasty, which ruled from 2100 to 1600 BC. They were concerned about the Yellow River's regular floods, which destroyed their crops. So they organised the people to build canals to re-direct the flood waters.

In about 1600BC, the Xia were overthrown by the Shang Dynasty. They ruled from 1600 to 1046 BC and were followed by the Zhou. By the time the Zhou took over, the Chinese had developed a complex, highly ordered culture. Once the Yellow River was under control, they were able to grow large crops of rice. Unless there was a natural disaster, such as a flood or drought, they usually had enough to eat.

They also had a very stable government. It was headed by the Emperor, who was believed to be semi-divine and so called the 'Son of Heaven'. He was assisted by a class of civil servants who were required to pass exams to get their jobs. This meant only the most able men were allowed to join the government.

All able-bodied men had to help keep public works, such as the canals, in good repair. So everyone had their part to play in maintaining order in society. The Chinese were very inventive. They developed gun-powder, fireworks and had a standardised currency partly based on banknotes. They also invented the printing press, which meant that scholars could publish useful books, such as manuals about farming, and local histories. It seems they invented pasta, although the Italians claim they were first. It was not until about 1500 AD that many of these things reached Europe.

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Another civilisation developed further east along the Indus River, in India and Pakistan. We know very little about its early history. The first people to live there were the Dravidians. As the ruins of their cities at Harappa and Moehnjo-daro show, they were a wealthy, cultured people. They were literate, but no-one has managed to read the script they used.

It seems, like the Minoans, they were over-run by invaders. They were the 'Aryans'. No-one is sure where the Aryans came from. They brought an entirely new culture to the Indus Valley and imposed it on the Dravidians. Its main feature was social hierarchy based on groups known as 'castes.' The most powerful class were the priests, who were called 'Brahmins'. Next were the soldiers, then the merchants and workers. Last of all were the 'Untouchables', who were excluded from society altogether.

The caste system was often very rigid. You usually had to stay into the caste you were born into. No matter how hard you worked, you could not move up to a higher caste. You could only marry another member of our own caste. So if you were a soldier and fell in love with a Brahmin girl, you could not get married.

The Aryans also brought their own language with them, Sanskrit. It has a very similar structure to the early Greek spoken by the Dorians. This indicates the Dorians may have been related to the Aryans or come from the same place as them. Historians think the Aryans may have also been Indo-Europeans.

The Aryans preserved details of their history and religious rites in a series of epics known as the 'Vedas'. The earliest and most famous is the Rig-Veda, which tells how the Aryans came to the Indus Valley and conquered a people called the 'Dasa'. It seems 'Dasa' may have been another name for the Dravidians, but this is not certain.

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Another group of Indo-Europeans called the 'Hitties' occupied Turkey, the land which joins Europe and Asia. The Hitties, like the Ayrans, were literate. But no-one has been able to read their elaborate script. They established their capital at Hattusa, which is not far from modern Ankara. We visited Hattusa's ruins while we were in Turkey in 2007. It is a very impressive site. There are the remains of large stone temples and fortifications. There is also an open air temple that was built inside an enclosure of natural rock into which the Hittites had carved pictures of their gods and kings.

The Hittites tried to expand further west in the 1270s BC, only to come into conflict with the Egyptians. Ultimately both the Egyptian and Hittite civilisations collapsed in about 1177 BC. It seems they, and a few other states, were invaded by a mysterious group called the 'Sea Peoples'. We don't know who they were or where they came from. More importantly, we don't know how they managed to topple such powerful states. Maybe they disrupted important trade routes: no-one knows.

We call this time the 'late Bronze Age', as it was getting towards the end of the time when many societies were using it to make their tools, pots and pans and weapons. This period brings us to the end of the first part of our survey. By this time, people had also settled many other parts of the Earth, including south-east Asia, Australia, northern Europe and the Americas. We'll pick up what happened there, along with the rest of the world up to now, in part II.

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