Welcome to Crash Course Big History

where today we're going to talk

about the Planet of the Apes films.

What's that?

Apparently those were not documentaries.

But there was an evolutionary process

that saw primates move out of East Africa

and transform the Earth into an actual planet of the apes.

But the apes are us.

And then we made the movie, and then some prequels

and some sequels and some reboots,

and now sequels to the reboots.

Man, I can't wait until I get to see the 2018 reboot

of this episode of Crash Course Big History.

I hear they get James Franco to play me.

So we're about halfway through our series,

and after five episodes involving no humans whatsoever,

today we are finally going to get some people!

Mr. Green, Mr. Green!

Why are we already at humanity?

I mean, if we're covering 13.8 billion years,

shouldn't humanity come in the last, like, two seconds

of the last episode?

I mean, humans are totally insignificant compared

to the vastness of the universe.

Like, we should be checking in on how Jupiter's doing.

Fair point, me from the past.

Jupiter, by the way, still giant and gassy.

There's two reasons why we focus a little more

on humanity in Big History.

The selfish reason is that we care about humans

in Big History because we are humans.

We are naturally curious to figure out where we belong

in the huge sequence of events beginning with the Big Bang.

Secondly, humans represent a really weird change

in the universe.

I mean, so far as we know, we are one

of the most complex things in the cosmos.

Whether you measure complexity in terms of biological

and cultural building blocks, or networks or connections,

I mean, we're kind of amazing.

Now, I realize that many of our viewers will be offended

by our human-centric bias, but humans are amazing.

I mean, we invented the Internet and we invented the animated GIF

and we inventedDr. Who, and then we invented Tumblr,

a place where all of these things can come together.

So 65 million years ago,

catastrophe wiped out the dinosaurs

and we saw the adaptive radiation

of a tiny shrew-like ancestor of humans

that would look more at home, like, next to a hamster wheel

than in your family album.

Let's set the stage in the Thought Bubble.

So, the slow waltz of plate tectonics continued

to pull Eurasia and the Americas apart,

expanding the Atlantic ocean.

Primate colonized the Americas and,

separated by the vast Atlantic,

continued their separate evolution

into the New World monkeys, which is not a band name,

although it should be.

Then around 45 million years ago,

Australia split from Antarctica and,

while mammals out-competed most marsupials in the Americas--

except animals like possums--

Australia saw an adaptive radiation of marsupials.

This of course meant that later, about 100,000 years ago,

when the Americas were having their share of mammoths

and saber-tooth tigers, Australia was having a spell

of gigantic kangaroos, marsupial lions,

and wombats the size of hippos.

Then somewhere around 40 million years ago,

India, which had been floating around the southern oceans

as an island, smashed into the Eurasian continent

with such force that it created

the world's tallest mountain range, the Himalayas.

Meanwhile in Africa, primates continued to evolve,

and 25 million to 30 million years ago,

the line of the apes diverged from the Old World monkeys

and, no, neither you nor a chimp is a monkey,

nor did we evolve from the monkeys that are around today.

Those are like our cousins.

Moreover, we did not evolve from chimpanzees.

The chimpanzee is a cousin, as well, not an uncle.

We are not more highly evolved than they are.

Instead, our lines of descent split off

from a common ancestor with chimpanzees

about 7 million years ago.

Then chimpanzees further split

into a separate species, the bonobos.

Knowing about this common ancestry tells us a lot

about our shared traits with other primates.

For instance, we all have fairly large brains relative

to our body mass.

We have our eyes in the front of our heads--

from the days when we hung out in trees

and depth perception was an excellent way

of telling how far away the next tree branch was

so as to prevent us from plummeting to our deaths--

and we also have grasping hands to make sure, you know,

that you could hold on to the branch in question.

Primates also have hierarchies-- social orders,

whether male or female led-- that determine

who gets primary access to food, mates, and other benefits.

Thanks, Thought Bubble.

So our closest evolutionary cousins, the chimpanzees,

can tell us a thing or two about shared behaviors.

For one thing, while all primates have a hierarchy

of alphas and betas, humans and chimps,

who share 98.4% of their DNA, are the most prone

to team up together and launch a revolution

against the alpha male.

We're also both prone to ganging up, roaming our territory,

and beating up unsuspecting foreigners of the same species,

and not for direct survival reasons.

Chimpanzees have been observed finding a lone chimp male

from another group and kicking, hitting,

and tearing off bits of his body

and then leaving the helpless victim to die of his wounds,

and humans definitely bear this stamp of our lowly origin where,

indeed, the imperfect step-by-step process

of evolution made us highly intelligent

but still with prefrontal cortexes too small

and adrenal glands maybe too big.

Aggression and bloodlust are definitely part

of our shared heritage,

and looking at more recent human history,

does that really surprise anyone?

Contrast that behavior for a moment

with the more peaceful bonobos, who are female-led and,

when a male in a group gets a bit pushy,

the females are prone to gang up and teach him a lesson.

When it comes to intergroup encounters in the wild,

the male bonobos seem tense around strangers at first

until, usually, the females from each group cross over

and just have sex with the newcomers,

completely diffusing the tension.

Talk about make love not war.

Bonobos are hippies.

While our common ancestor with the chimpanzees

around 7 million years ago was more suited to living in forests

and seeking refuge from danger by climbing trees,

climate change in East Africa made things colder and drier

and many forests were replaced by woodlands

in wide-open savannah.

Life in the savannah meant our ancestors needed to run

from predators rather than climbing trees,

so our lines shifted away from the bow-legged stance

reminiscent of chimpanzees and developed bipedalism,

where our locomotion came from legs

that were straight and forward-facing.

There's still some debate about when bipedalism first began,

but we know that by the first australopithecines

around 4 million years ago, our evolutionary line was bipedal.

This also freed up our hands.

Australopithecines were not very tall,

standing only just above a meter,

or just over three and a half feet,

and had brains only a little bigger than modern chimpanzees.

They were largely herbivores with teeth adapted

for grinding tough fruits and leaves.

Australopithecines may have communicated

through gestures and primitive sounds,

but their higher larynx meant

that they couldn't make the range of sounds required

for complex language.

There was probably a lot of pointing and grunting going on,

kind of like me before 6:00 a.m.

By 2.3 million years ago,Homo habilisarrived on the scene.

They weren't much taller than australopithecines,

but they had significantly larger brains,

though still a lot smaller than later species.

Excitingly,Homo habilisis known to have hit flakes off

of stones to use them for cutting.