Let me begin with a story.
A long time ago,
there was an artist
in the streets of Baghdad.
He was an expert
in making jewelery.
The artisan was famous for
making the most popular pieces
on the market.
Whether it was a
necklace or an earring,
he would always sell
better than everyone else,
and left his rivals
wondering about his secret.
To find out his secret,
let's look at his shop.
Here is how he does it.
He has a collection
of earrings, and say
the one on the top left corner
is currently selling well.
The artisan's
strategy is to make
more copies of the pieces
that sell best and fewer
of the pieces that
sell less successfully.
There are three principles that
the artisan's strategy relies
on.
First, he has a lot
of different designs,
so he can find out the
design that is liked best.
If he had only one
design, he could easily
have gone broke, because if
the design wasn't popular,
he couldn't sell any.
Second, the artisan must be
able to make more pieces.
And third, he must somewhat
conserve the design
so that the customers
still like it.
Of course, he could sometimes
change the bestselling design
a little to create more variety,
as you see in the bottom right.
Remember, the three
properties that were important
here are that there's
a variety of choices,
new copies are made
after each sale,
and the copies inherit
most of their properties
from the original design.
The contents of the
shop change over time,
and we can say that
the jewelery evolves
to fit the customer's taste.
A similar process
was first observed
in nature by Darwin and Wallace
more than 150 years ago.
It is called natural selection.
In nature, however, things
are not bought and sold.
Instead, the currency is what
biologists call fitness--
not quite the fitness
you see at the gym,
but here, the fit
individual is someone
that can have more
surviving children.
Individuals with
greater fitness are
more likely to survive
and have children,
so they are represented more in
the population as time goes by.
To understand this better,
let's look at an example.
This white mouse
lives in the desert,
and is preyed upon by
vultures and eagles.
The white color of its fur makes
it easy to spot by the vulture.
This is controlled by a gene.
But even small although rare
changes in the gene when
they are passed on
to the offspring
can make the fur color change.
In this environment, because
the background is brown,
a brown fur would
protect the mouse
from the eyes of the predator.
In this case, we say that the
brown fur gives the fitness
advantage to the mouse.
Let's look at what happens here.
Starting from a white
father, the brown baby mouse
is much more likely to survive
than his white siblings.
The white mice are more often
preyed upon by the eagle
because they are conspicuous.
After a few generations,
there are many more
surviving brown rice
than white mice,
because natural selection has
caused the mouse population
to adapt to the environment.
Going back to the properties we
learned before, the variation
here is created by
the changes in genes
that create the two colors.
The inheritance means white
mice make mostly white offspring
and brown mice make
mostly brown offspring.
Producing offspring already
satisfies multiplication.
Although predation can
be a drive for selection,
as we saw in the mouse example,
it is not the only cause.
As you may know,
the male peacock
has a very large,
embellished tail
with no apparent use
in its daily life.
Why is this?
Well, the peacock lady
you see on the left
tends to be very, very
picky about the gentlemen
she decides to mate with.
Therefore, male
peacocks must be very
good at convincing her to mate.
This is where the
tail is useful.
The tail makes them
more attractive.
But the tail didn't
appear overnight.
At one point, peacocks
had tails similar to those
of chickens or turkeys, like
the male on the top right.
However, maybe those
peacocks with a slightly more
embellished tail managed
to win over more ladies,
and therefore,
left more children
in the next generation.
Once again, even among
the new generation,
the ladies preferred the males
with even prettier and more
spectacular tails, which means
a larger tail can provide
a better fitness for the guys.
Through natural
selection over thousands
or even millions of years,
the male peacock's tail
became more and more
spectacular just
to attract the picky ladies.
So in conclusion,
natural selection
is one of the most important
forces in evolution.
By this process, the
fitter individuals
are more likely to
survive and reproduce.
Hope you enjoyed
the video, and see
where you can find
natural selection at work.
It's everywhere.
