Human Evolution: Crash Course Big History #6


In which John Green and Hank Green teach you about how human primates moved out of Africa and turned Earth into a real-life Planet of the Apes. And the apes are people! John and Hank teach you about how humans evolved, and the sort of tricks they picked up along the way like complex tool use, big brains, and fighting. Our ancestors adapted to the grasslands of Africa, and went through several iterations including Australopithecus, Homo Habilis, and Homo Ergaster/Erectus. Our ancestors tamed fire, made pressure flake tools, and eventually smartphones.

Transcript Provided by YouTube:

00:00
Hi, I’m John Green. Welcome to Crash Course Big History Project where today we’re going
00:04
to talk about the Planet of the Apes films. – What’s that? Apparently, those were not documentaries.
00:10
But there was an evolutionary process that saw primates move out of East Africa and transform
00:15
the earth into an actual planet of the apes…but the apes are us.
00:19
And then we made the movie and then some prequels and some sequels and some reboots and now sequels to the reboots.
00:25
Man, I can’t wait until I get to see the 2018 reboot of this episode of Crash Course Big
00:29
History I hear they get James Franco to play me.
00:32
[Theme Music]
00:41
So we’re about halfway through our series and after five episodes involving no humans
00:45
whatsoever today we are finally gonna get some people.
00:48
Mr. Green, Mr. Green! Why are we already at humanity, I mean if we’re covering 13.8 billion
00:53
years shouldn’t humanity come in like, the last two seconds of the last episode? I mean
00:57
humans are totally insignificant compared to the vastness of the universe, like we should
01:01
be checking in on how Jupiter’s doing.
01:03
Fair point, Me From the Past; Jupiter by the way, still giant and gassy.
01:06
There’s two reasons why we focus a little more on humanity in Big History; the selfish
01:10
reason is that we care about humans in Big History because we are humans. We are naturally
01:15
curious to figure out where we belong in the huge sequence of events beginning with the big bang.
01:20
Secondly, humans represent a really weird change in the universe. I mean, so far as we
01:25
know, we are one of the most complex things in the cosmos.
01:29
Whether you measure complexity in terms of biological and cultural building blocks or
01:33
networks or connections, I mean, we’re kind of amazing! Now I realize that many of our
01:39
viewers will be offended by our human-centric bias, but humans are amazing. I mean, we invented
01:44
the internet and we invented animated GIF and we invented Dr. Who and then we invented
01:51
Tumblr, a place where all of these things can come together!
01:53
So 65 million years ago, catastrophe wiped out the dinosaurs and we saw the adaptive
01:58
radiation of a tiny shrew-like ancestor of humans that would look more at home like,
02:04
next to a hamster wheel than in your family album. Let’s set the stage in the Thought Bubble.
02:08
So the slow waltz of plate tectonics continued to pull Eurasia and the Americas apart expanding
02:14
the Atlantic Ocean, primates colonized the Americas, and separated by the vast Atlantic, continued
02:20
their separate evolution into the new world monkeys — which is not a band name, although it should be.
02:25
Then around 45 million years ago, Australia split from Antarctica and while mammals out-competed
02:31
most marsupials in the Americas (except animals like possums), Australia saw an adaptive radiation
02:36
of marsupials. This, of course, meant that later, one-hundred thousand years ago when
02:40
the Americas were having their share of mammoths and saber-tooth tigers, Australia was having
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a spell of gigantic kangaroos, marsupial lions, and wombats the size of hippos.
02:50
Then, somewhere around forty million years ago, India, which had been floating around
02:54
the southern oceans as an island, smashed into the Eurasian continent with such force
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that it created the world’s tallest mountain range, the Himalayas.
03:02
Meanwhile, in Africa, Primates continued to evolve and twenty-five to thirty million years
03:06
ago, the line of the apes diverged from theold-world monkeys and no, neither you, nor a chimp,
03:13
is a monkey, nor did we evolve from the monkeys that are around today – those are like our cousins.
03:18
Moreover, we did not evolve from chimpanzees, the chimpanzee is a cousin as well, not an
03:24
uncle. We are not more highly evolved than they are; Instead, our lines of descent split
03:29
off from a common ancestor with chimpanzees about seven million years ago. Then chimpanzees
03:34
further split into a separate species, the Bonobos. Knowing about this common ancestry
03:39
tells us a lot about our shared traits with other primates.
03:42
For instance, we all have fairly large brains, relative to our body mass, we have our eyes
03:46
in the front of our heads from the days when we hung out in trees and depth perception
03:50
was an excellent way of telling how far away the next tree branch was so as to prevent
03:54
us from plummeting to our deaths, and we also have grasping hands, to make sure, you know,
03:58
that you could hold onto the branch in question. Primates also have hierarchies, social orders
04:02
whether male or female led, that determine who gets primary access to food, mates, and other benefits.
04:09
Thanks Thought Bubble! So, our closest evolutionary cousins, the chimpanzees, can tell us a thing
04:13
or two about shared behaviors. For one thing, while all primates have a hierarchy of alphas
04:18
and betas, humans and chimps, who share 98.4% of their DNA, are the most prone to team up
04:24
together and launch a revolution against the alpha male. We’re also both prone to ganging
04:29
up, roaming our territory, and beating up unsuspecting foreigners of the same species,
04:33
and not for direct survival reasons.
04:35
Chimpanzees have been observed finding a lone chimp male from another group and kicking,
04:39
hitting, and tearing off bits of his body and then leaving the helpless victim to die
04:44
of his wounds, and humans definitely bear this stamp of our lowly origin, where indeed,
04:49
the imperfect step-by-step process of evolution made us highly intelligent, but still, with
04:54
prefrontal cortex’s too small, and adrenal glands maybe too big.
04:57
Aggression and blood lust are definitely part of our shared heritage, and, looking at more
05:01
recent human history, does that really surprise anyone? Contrast that behavior, for a moment,
05:05
with the more peaceful Bonobos, who are female-led, and when a male in her group gets a bit pushy,
05:09
the females are prone to gang up and teach him a lesson. When it comes to inter-group
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encounters in the wild, the male Bonobos seem tense around strangers at first, until usually,
05:18
the females from each group cross over and just have sex with the newcomers, completely diffusing
05:22
the tension. Talk about make love, not war – Bonobos are hippies.
05:26
While our common ancestor with chimpanzees around seven million years ago was more suited
05:30
to living in forests and seeking refuge from danger by climbing trees, climate change in
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East Africa made things colder and drier, and many forests were replaced by woodlands
05:39
and wide-open savanna. Life in the savanna meant our ancestors needed to run from predators
05:43
rather than climbing trees, so our line shifted away from the bow-legged stance reminiscent
05:47
of chimpanzees, and developed bipedalism, where our locomotion came from legs that were
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straight and forward-facing.
05:53
There’s still some debate about when bipedalism first began, but we know that by the first
05:56
australopithecines around four million years ago, our evolutionary line was bipedal, this
06:01
also freed up our hands.
06:02
Australopithecines were not very tall, standing only just above a meter, or just above 3.5
06:07
feet, and had brains only a little bigger than modern chimpanzees. They were largely
06:11
herbivores with teeth adapted for grinding tough fruits and leaves. Australopithecines
06:15
may have communicated through gestures and primitive sounds, but their higher larynx
06:19
meant that they couldn’t make the range of sounds required for complex language. There
06:22
was probably a lot of pointing and grunting going on. Kinda like me, before 6 am.
06:27
By 2.3 million years ago, homo habilis arrived on the scene. They weren’t much taller than
06:31
australopithecines, but they had significantly larger brains – though still a lot smaller
06:35
than later species. Excitingly, homo habilis is known to have hit flakes off of stones
06:40
to use them for cutting. Now, lots of species use tools, for instance chimpanzees use sticks
06:45
for fishing termites out of the ground, they use rock hammers and leaf sponges and branch
06:49
levers and banana leaf umbrellas. A lot of these skills don’t seem to arise spontaneously,
06:53
just because of the intelligence of individuals, but, like in the case of termite fishing,
06:57
chimpanzees pass the information on by imitation – primate see, primate do.
07:02
In a way, this social learning is sort of cultural, yet, succeeding generations of chimpanzees
07:06
don’t accumulate information, tinker with it, and improve upon it, so that after 100
07:10
years, chimpanzees are owners of highly efficient and wealthy termite fishing corporations.
07:14
Similarly, as impressive as homo habilis stone-working abilities are, we see very little sign of
07:19
technological improvement over the thousands and thousands of years that habilis existed.
07:24
Same goes for homo ergaster erectus, who was around 1.9 million years ago.
07:28
Homo ergaster erectus had an even bigger brain, was taller, and they even seemed intelligent
07:33
and adaptable enough to move into different environments across the old world. They may
07:37
have even begun our first clumsy attempts at fire, which is vital for cooking meat and
07:41
vegetables, opening up opportunities for more energy and even more brain growth.
07:45
But still, there’s not much sign of technological improvement, their tools got the job done,
07:49
if it ain’t broke, don’t fix it.
07:50
Yet 1.78 million years ago, we do see homo ergaster creating a wide new range of teardrop
07:55
hand axes in Kenya. By one-point-five 1.5 million years ago, these teardrop axes had
08:00
rapidly become common, and had improved in quality and were shaped with a flat edge into
08:04
multi-purpose picks, cleavers, and so forth.
08:07
Archaeologists see this as the first possible sign of tinkering and improvement of technology
08:11
that may have been transmitted by social learning. A faint glimmer of something new. Why is this important?
08:17
Well, humans didn’t get to where we are because we’re super-geniuses. It’s
08:20
not like invented the Xbox One out of the blue one day, it was an improvement upon the
08:24
Xbox 360 which was an improvement upon earlier consoles, arcade machines, computers, and
08:29
backward onto the dawn of video games. In the same way, we didn’t just invent our
08:33
modern society by sudden inspiration, it’s the result of 250,000 years of tinkering and
08:39
improvement. This is where accumulation matters – it’s called collective learning, the ability
08:43
of a species to retain more information with one generation than is lost by the next. This
08:48
is what has taken us, in a few thousand years, from stone tools to rocket engines to being
08:53
able to have the Crash Course theme song as your ringtone. Progress!
08:56
If there was collective learning in homo ergaster, it was very slow and very slight. This may
09:01
have been due to limitations on communication, abstract thought, group size, or just plain
09:05
brain power. But over the next two million years, things started to pick up. Homo antecessor,
09:10
Homo Heidelbergensis and the Neanderthals developed the first systematically controlled
09:14
use of fire in hearths, the first blade tools, the earliest wooden spears, the earliest use
09:19
of composite tools, where stone was fastened to wood, all before homo sapiens were ever
09:25
heard of, around 250,000 years ago.
09:27
Neanderthals even moved into colder climates, where they were compelled to invent clothing,
09:31
they used complex tool-manufacture to produce sharp points and scrapers and hand-axes and
09:36
wood handles, and they improved their craft over time.
09:39
While evolution by natural selection is a sort of learning mechanism that allows a species
09:44
to adapt generation after generation, with a lot of trial and error, and death – collective
09:49
learning allows for tinkering, adaptation, and improvement on a much faster scale with
09:54
each generation and across generations without waiting for your genes to catch up.
09:59
Anatomically similar homo sapiens have been around for about 250,000 years, and throughout
10:03
that time, we’ve been expanding our toolkit from stone tools to shell fishing to trade
10:08
and actual fishing, mining, and by 40,000 years ago we had art, including cave images,
10:13
decorative beads and other forms of jewelry, and even the world’s oldest known musical
10:18
instruments – flutes carved from mammoth ivory and bird bones.
10:21
All this stuff came about as a result of collective learning. As long as you have a population
10:26
of potential innovators, who can keep dreaming up new ideas and remembering old ones and an
10:30
opportunity for those old innovators to pass their ideas onto others, you’re likely to
10:35
have some technological progress.
10:37
These mechanisms are still working today – we’ve got over seven billion potential innovators on
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this planet, and almost instantaneous communication, allowing us to do so many marvelous things
10:47
including teach you about Big History on the internet.
10:50
So life for early humans was pretty good, like foraging didn’t require particularly
10:55
long hours – the average work day for a forager was about 6.5 hours. When you compare that
11:00
to an average of 9.5 hours for a peasant farmer in medieval Europe, or the average of nine
11:04
hours for a typical office worker today, foraging seems downright leisurely.
11:09
Quick aside: I work thirty minutes a day less than a peasant farmer in medieval Europe?
11:14
That’s not progress! Stan, I want more time off!
11:17
Stan just pointed out that I have a chair, something that peasant farmers in medieval
11:20
Europe did not enjoy, and I want to say that I’m very grateful for my chair.
11:23
Thank you for my chair, Stan.
11:24
Anyway, a forager would go out, hunt or gather, come home, eat, spend time with the family,
11:29
dance, sing, tell stories, and foragers were also always on the move, which made it less
11:34
likely that they’d contaminate their water, or sit around waiting for a plague to develop.
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And with their constant walking and their varied diet, foragers were in many ways healthier
11:44
than the peasants of ancient civilizations. There were also, in some ways, healthier than
11:47
us, but we have antibiotics for now, so we live longer, for now.
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The classic view of foraging life is best described by Thomas Hobbes, who wrote:
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“No arts, no letters, no society, and which is worst of all continual fear and danger
12:02
of violent death and the life of man, solitary, poor, nasty, brutish, and short.”
12:09
Except, not really. I mean, life for the average person in twelfth century France was also
12:13
a smidge nasty, brutish, and short, and the lack of wealth disparity in foraging cultures
12:18
may imply greater equality between social rankings and even between the genders since
12:22
female gatherers appear to be responsible for the majority of food collected, rather
12:26
than the hunting males. And from that perspective, life was kind of ruined by the advent of agriculture
12:32
and then, later, with states, as Jean-Jacques Rousseau said,
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“The first person, who having enclosed a plot of land, took it into his head to say, ‘this
12:40
is mine’ and found people simple enough to believe him, was the true founder of civil
12:45
society. What crimes, wars, murders, what miseries and horrors would the human race
12:50
have spared, had someone pulled up the stakes or filled in the ditch and cried out to his
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fellow men: ‘do not listen to this imposter, you are lost if you forget that the fruits of the
13:00
Earth belong to all, and the Earth to no one’”
13:03
and thus summarizes one of the great debates in the world of political science. Man, Big
13:06
History discusses everything! Now, it’s possible that neither Rousseau nor Hobbes was completely
13:11
correct, and that, like, private property and agriculture didn’t create the glory days or end them.
13:17
Like, as previous mentioned, all primates have a dominance hierarchy of some kind. Also,
13:22
you don’t need a wealth disparity to drive human beings to hurt each other – like, surveys
13:26
of excavated remains from the paleolithic indicate a murder rate that was possibly as
13:30
high as ten percent. Now, those statistics are still disputed, but despite the relatively
13:34
short work day, life in the paleolithic sounds a lot less appealing when you consider the
13:38
high murder rate, and also, the occasional infanticide. That’s not even to mention the
13:42
old or disabled people who, when they couldn’t keep up anymore, were abandoned to die in
13:46
the wild. I can’t help but feel that I might not have thrived in the paleolithic what with
13:49
my visual impairment and general lack of interest in hunting.
13:53
Anyway, we call this the Hobbes vs. Rousseau debate, and it’s still unresolved. I mean,
13:57
humans may have been corrupted in many ways by society, on the other hand, it’s possible
14:02
a lot of the crimes and follies of human history may just be symptoms of our coping with the
14:07
bad wiring left to us by evolution.
14:10
You know, humans are a bit of an obsolete machine, we aren’t particularly well-suited
14:14
to the many lifestyle changes that have happened in the past few thousand years – faster than
14:18
our genes can keep pace with. But how you interpret the lives of early human foragers
14:22
largely determines your view of history and also the fundamental nature of the human character.
14:27
Ask yourself which side you sit on: Is humanity fundamentally good and corrupted by technology
14:34
and modern social orders, or are we fundamentally flawed and in need of some sort of structure
14:38
and authority? Or is there some kind of both/and way of addressing the question? Here at Crash Course,
14:43
we don’t have answers, but we are grateful that you’re pondering these questions with us.
14:48
In any case, collective learning was really good for our survival, but then, 74,000 years
14:53
ago, disaster struck. A super-eruption at Mt. Toba on the island of Sumatra in present-day
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Indonesia clouded the skies with ash and cooled the climate. Plants and animals, a.k.a. food, died
15:04
off and genetics studies showed that this reduced the human population to a few thousand
15:09
people. So as a result of this, we aren’t exactly inbred, but there’s more genetic diversity
15:14
between two of the major groups of chimpanzees in Africa than there is in all of humanity.
15:19
So this small group heroically recovered and spread out of Africa 64,000 years ago, colonizing
15:25
diverse environments and continuing to innovate. For 13.8 billion years since the beginning
15:30
of the universe, complexity had been rising in a powerful crescendo, but in the space
15:34
of a few millennia, collective learning was about to make things really bonkers.
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More on that next time.


This post was previously published on YouTube.

Photo credit: Screenshot from video.

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