Ok, go to the window. Or better yet, step
outside. A squirrel darts past. Trees and
weeds surge up towards the sky. Birds tickle
the air. Get down on the ground and there’s
more—worms wriggling, mushrooms sprouting,
beetles crawling. There’s stuff you can’t
even see, like bacteria. And everywhere you
go on this planet—on land, underground,
in the air, and in the water—there’s more
life to be found.
And all of it—even you—is shaped by the
most incredible of forces. Evolution.
Evolution essentially multiplies majesty by
majesty by majesty.
And our understanding of all that majesty—it
goes back to the mid-1800s, when an English
20-something, a guy named Charles Darwin,
got an invitation he couldn’t refuse.
To travel ’round the world. It was 5 years.
And that voyage made him into a thinker.
He was just a great naturalist—he saw things
out in nature, and he asked: “Why?”
As in, why is there such a stunning diversity
of life? Why are similar looking species sometimes
located on opposite sides of the planet?
It was Darwin and Alfred Russel Wallace who
independently puzzled out a mechanism behind
evolution.
Which was natural selection.
Natural selection just means that nature—the
natural environment—is what’s selecting
which organisms survive long enough to reproduce.
And it depends on two key ingredients.
The first is some way of getting features,
or traits, to be inherited from one generation
to the next, which usually means reproduction.
The second is variation. If organisms were
to make exact duplicates of themselves every
time they reproduced, nothing would change.
There’d be no elephants, no pine trees,
no humans – we’d still just be single-celled
proto-organisms.
Now, the environment can’t support every
individual that’s born. Maybe it’s too
dry or too wet for some of them, maybe all
the food’s up in tall trees, maybe there’s
not enough food, or maybe it’s just really
cold. Whatever it is, organisms compete for
resources. And this is where selection comes
in.
For instance, scientists believe that a few
hundred thousand years ago, before there were
polar bears, some brown bears got stranded
in the Arctic. The few that survived likely
had fur coats that were a bit thicker, and
lighter in color than the others. That would’ve
kept them warmer, and helped them blend in
with the snow to sneak up on prey more easily.
The point is—not all variations make it.
And the things that survive go on to reproduce.
In other words, survival of the fittest. Which
doesn’t necessarily mean the biggest or
the strongest.
Fittest in an evolutionary sense is whoever
has the most descendants.
In the Arctic, the bears with thicker and
whiter coats survived more often and had more
offspring—offspring that inherited the thicker
and whiter fur. And gradually, other changes
accumulated too. Until this population became
a separate species from the brown bears.
However, if we were to swap out the snow for
a forest, having polar bear-like fur would
likely be a bad thing.
In other words, evolution doesn’t progress
in one fixed direction—but it’s not entirely
random either. With so many environments selecting
for all kinds of traits, evolution has resulted
in the countless species that have lived on
Earth.
Now, Darwin wrote these ideas down.
He was not a visual man.
So when he did bother to draw something, people
took notice. Like this image he sketched in
one of his notebooks.
It’s a tree.
And it tells us how things are related. That
is, they all can be traced back to a common
ancestor.
That ancestor—the first living organism
on our planet – is at the base of the tree
trunk. Here’s another view of this so-called
phylogenetic tree. As life’s evolved over
the last 3.8 billion years, new species have
branched off, leading to entire lineages of
different organisms.
Every branching point in that tree is a story.
Stories of global domination, of extinction.
Stories of beauty, and of remarkable adaptation
to an ever-changing world.
I mean, the goal of the tree of life is: try
to understand how every species is related
to each other. The breadth of this—that
is amazing.
And that’s where you come in. In NOVA’s
Evolution Lab, you’ll be climbing around
the tree of life to build out portions of
that tree. To see how evolution really works,
and understand why it matters to you. Like:
did you eat a dinosaur last night for dinner?
Can you save someone from a venomous snakebite?
Or do you have a Neanderthal ancestor?
Play this Lab, build the tree of life—which
is your family tree, and discover just how
connected you are to everything that’s alive
and everything that’s ever lived.
