Crash Course Big History #6: Human Evolution


Hi, I’m John Green. 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. Now, lots of species used tools. For instance,
chimpanzees use sticks for fishing termites out
of the ground, and they use rock hammers
and leaf sponges and branch levers
and banana leaf umbrellas. A lot of these skills don’t
seem to arise spontaneously just because of the intelligence
of individuals, but, like in the case
of termite fishing, chimpanzees pass the information
on by imitation: primate see, primate do. In a way, this social learning
is sort of cultural, yet succeeding generations
of chimpanzees don’t accumulate information,
tinker with it and improve upon it so
that after a hundred years, chimpanzees are owners
of highly efficient and wealthy termite-fishing
corporations. Similarly, as impressive
asHomo habilis’ stone-working abilities are,
we see very little sign of technological improvement
over the thousands and thousands of years thathabilisexisted. Same goes for
Homo ergaster erectus, who was around 1.9 million years
ago. Homo ergaster erectushad
an even bigger brain, was taller, and they
even seemed intelligent and adaptable enough to move
into different environments across the old world. They may have even begun our
first clumsy attempts at fire, which is vital for cooking meat
and vegetables, opening up opportunities
for more energy and even more brain growth. But still, there’s not much sign
of technological improvement. Their tools got the job done–
if it ain’t broke, don’t fix it. Yet, 1.78 million years ago,
we do seeHomo ergaster creating a wide range of
tear-drop hand axes in Kenya. By 1.5 million years ago, these tear drop axes
had rapidly become common and had improved in quality
and were shaped with a flat edge
into multi-purpose picks, cleavers, and so forth. Archeologists see this as: A faint glimmer
of something new. Why is this important? Well, humans didn’t get
to where we are because we’re super geniuses. It’s not like the Xbox 1
was just invented out of the blue one day,
it was an improvement upon the Xbox 360,
which was an improvement upon earlier consoles,
arcade machines, and computers and backward
onto the dawn of video games. In the same way we didn’t just
invent our modern society by sudden inspiration. It’s the result of 250,000 years
of tinkering and improvement. This is where
accumulation matters. It’s called collective learning: This is what has taken us
in a few thousand years from stone tools to rocket
engines to being able to have theCrash Coursetheme
song as your ringtone. Progress. If there was collective
learning inHomo ergaster, it was very slow
and very slight. This may have been due to
limitations on communication, abstract thought, group size,
or just plain brain power. But over the next two million
years things started to pick up. Homo antecessor,
Homo heidelbergensis, and the Neanderthals
developed the first systematically controlled use
of fire and hearth, the first blade tools,
the earliest wooden spears, the earliest use
of composite tools where stone was
fastened to wood, all beforeHomo sapiens
were every heard of around 250,000 years ago. Neanderthals even moved
into colder climates where they were compelled
to invent clothing. They used complex
tool manufacture to produce sharp points
and scrapers and hand axes and wood handles, and they improved
their craft over time. While evolution
by natural selection is a sort of learning mechanism
that allows a species to adapt generation
after generation with a lot of trial
and error and death, collective allows
for tinkering adaptation and improvement
on a much faster scale with each generation
and across generations without waiting for
your genes to catch up. Anatomically-similarHomo
sapienshave been around for about 250,000 years
and throughout that time, we’ve been expanding our tool
kit from stone tools to shell fishing to trade
and actual fishing, mining, and by 40,000 years ago, we had
art, including cave images, decorative beads, and
other forms of jewelry, and even the world’s oldest
known musical instruments– flutes carved from mammoth
ivory and bird bones. All this stuff came about as a
result of collective learning. As long as you have a population
of potential innovators who can keep dreaming up new
ideas and remembering old ones and an opportunity
for those innovators to pass their ideas on
to others, you’re likely to have some
technological progress. These mechanisms are still
working today. We’ve got over 7 billion
potential innovators on this planet and almost
instantaneous communication, allowing us to do so many
marvelous things, including teach you about
Big History on the internet. So life for early humans
was pretty good. Like, foraging didn’t require
particularly long hours. The average workday
for a forager was about six-and-a-half hours. When you compare that to an
average of nine-and-a-half hours for a peasant farmer in medieval
Europe or the average of nine hours for a typical
office worker today, foraging seems
downright leisurely. Quick aside– I work 30
minutes a day less than a peasant farmer
in medieval Europe? That’s not progress. Stan, I want more time off! Stan just pointed out
that I have a chair, something that peasant farmers in medieval Europe
did not enjoy, and I want to say that I’m very
grateful for my chair. Thank you for my chair, Stan. Anyway, a forager would go out,
hunt or gather, come home, eat, spend time with the family,
dance, sing, tell stories. And foragers were also
always on the move, which made it less likely that
they’d contaminate their water or sit around waiting
for a plague to develop. And with their constant walking
and their varied diet, foragers were
in many ways healthier than the peasants of
ancient civilizations. They were also in some ways
healthier than us, but we have antibiotics for now,
so we live longer, for now. The classical view of foraging
life is best expressed by Thomas Hobbes who wrote,
“No arts, no letters, “no society, and, which is worst
of all, continual fear “and danger of violent death,
and the life of man, solitary, poor, nasty,
brutish, and short.” Except not really. I mean, life
for the average person in 12th century France
was also a smidge nasty, brutish, and short. And the lack of wealth disparity
in foraging cultures may imply greater equality
between social rankings and even between the genders,
since female gatherers appear to be responsible for the
majority of food collected rather than the hunting males. And from that perspective,
life was kind of ruined by the advent of agriculture
and then, later, with states. As Jean-Jacques Rousseau said,
“The first person who, “having enclosed a plot of land,
took it into his head to say, “‘This is mine’
and found people simple enough “to believe him was the true
founder of civil society. “Do not listen to this imposter. “You are lost if you forget
that the fruits of the earth belong to all
and the earth to no one.” And thus summarizes one
of the great debates in the world
of political science. Man, Big History discusses
everything. Now it’s possible that neither
Rousseau nor Hobbes was completely correct and that,
like, private property and agriculture didn’t create
the glory days or end them. Like, as previously mentioned, all primates have a dominance
hierarchy of some kind. Also, you don’t need
a wealth disparity to drive human beings
to hurt each other. Like, surveys of
excavated remains from the Paleolithic
indicate a murder rate that was possibly
as high as 10%. Now, those statistics
are still disputed, but despite the relatively
short work day, life in the Paleolithic
sounds a lot less appealing when you consider
the high murder rate and also the occasional
infanticide. That’s not even to mention
the older disabled people, who, when they couldn’t
keep up anymore, were abandoned to die
in the wild. I can’t help but feel
that I might not have thrived in the Paleolithic what
with my visual impairment and general lack of
interest in hunting. Anyway, we call this the Hobbes
versus Rousseau debate and it’s still unresolved. I mean, humans may
have been corrupted in many ways by society. On the other hand, it’s possible
a lot of the crimes and follies of human history may just be
symptoms of our coping with the bad wiring left
to us by evolution. You know, humans are a bit
of an obsolete machine. We aren’t particularly
well-suited to the many lifestyle changes
that have happened in the past few
thousand years faster than our genes can
keep pace with. But how you interpret the lives of early human foragers largely
determines your view of history and also the
fundamental nature of the human character. Ask yourself which
side you sit on. Is humanity fundamentally good
and corrupted by technology and modern social orders,
or are we fundamentally flawed and in need of some sort of
structure and authority? Or is there some kind
of both/and way addressing the question? Here atCrash Course,
we don’t have answers, but we are grateful that you’re
pondering these questions with us. In any case, collective
learning was really good for our survival, but then,
74,000 years ago, disaster struck. A super-eruption at Mount Toba
on the island of Sumatra in present-day Indonesia
clouded the skies with ash and cooled the climate. Plants and animals–
a.k.a. food– died off,
and genetic studies show that this reduced
the human population to a few thousand people. So as a result of this,
we aren’t exactly inbred, but there’s more genetic
diversity between two of the major groups
of chimpanzees in Africa than there is in all
of humanity. So this small group heroically
recovered and spread out of Africa 64,000 years ago,
colonizing diverse environments and continuing to innovate. For 13.8 billion years since
the beginning of the universe, complexity had been rising
in a powerful crescendo, but in the space
of a few millennia, collective learning was about
to make things really bonkers. More on that next time.

Posts Tagged with…

Reader Comments

  1. Lauren Noel

    Thank you so much for doing episodes on evolutionary bio! I'm taking the online course for evobio this semester and the professor doesn't post recordings of lectures…which is the best way I retain this kind of information. CC to the rescue! <333

  2. musgrave000

    Wow guys, terrific job! This is the perfect start for people just getting into the history of human evolution. I even learned a few things myself! =)

  3. Ed Gloss

    I think we're the most amazing objects in the universe because we are the remnants of dead stars and have evolved to the point where we figured that out. There could always be beings that exploded those stars for the purpose of creating us which might be more amazing but given that I only know life on our planet with certainty I'll remain biased.

  4. Josh Costanza

    There is a new theory that bipedalism was not an adaptation for a dryer, Serengeti environment.  Instead, like Gould's punctuated equilibrium, small changes in the location of the spine entry in the skull and changes to the pelvis allowed for primates to stand up straight for longer periods, and thus become more attractive sexual partners.  This would certainly be a good explanation for the existence of Sahelanthropus tchadensis or Orrorin tugenensis, both of which existed during a period of lush woodlands and ample water sources.

    Once the climate changed circa 4.4 mya, the bipedal ape species exploded as sexual evolution changed into an adaptation necessary for survival.

  5. KingdomofSmileys

    Evolution starts with the evidence and determines a conclusion from that evidence.
    Creationism starts with a conclusion and desperately tries to find evidence to support it, and if evidence arises that doesn't support it it is thrown out and ignored.

    Which makes more sense to believe?

  6. WH1PP3DCR34M

    I can't find the answer anywhere because I don't really know how to word it, but how long would the Americas and Old World have had to be separated before the people would NOT able to breed and would be completely different species?

  7. Jake Pau

    The fossil records show different results whether you are a creationist or evolutionist. Evolutionist look at a fossils and think millions of years and a Creationist can see the SAME fossil and think thousands of years. We have the same fossils, not two separate piles.

  8. Jillian walker

    Plate tonics is such a big lie. There is no planet in the galaxy that is shaped like a ice cream cone.  One giant island and the rest is water. AToms are thought to be round and combining them together would be like a snowball.

  9. Christina Ho

    So does that mean collective learning stopped with Africans and South Americans? Or at least until Europeans showed up?

  10. DDdastard06

    Humanity is certainly flawed but I don't think appeals to authority is the answer. Or building a social system that exacerbates our flawed aspects and suppresses the good ones.

  11. Kagius23

    Hi Mr. Green.
    Random question. During your teams research, have you come across eating habits of humans or earlier versions of ourselves?

    I only ask because both my niece and nephew can't hold still while eating. Is there any evidence that we used to walk while eating? That's a simplified question, but I suppose another way to state it is… When did we begin sitting at a table like area while eating? Has it always been a social event? Is there any evidence that eating on the go was a norm?

  12. Joh Drinda

    Here's how to claim your share in your evolution process: aim to dismantle your inherited, negative traits and try to develop the positive ones. This will make you a better person and nature's laws are going to reward you (and punish if you fail) for doing so.

  13. My Name

    This is a response to all Christians that have left comments….

    I'm not sure why you get upset at the fact that people believe in evolution. Man has been trying to do things itself since time began. Even in the Old Testament when God was very much interacting "face to face" with people they still worshiped other gods or ignored God all together. This is nothing new. I've learned over the years that people don't want to believe in God simply because they don't want the accountability that comes from being a Christian. That moral tug that says, hey don't do that it's a sin and God doesn't want you to, even though no one is around or no one would say other wise. If people want to believe in no God then that's how it is. It clearly says in the Bible few will enter, Matthew 7:14. My point is no need to get offended or angry. To those that don't believe in God, no reason to get offended or angry at me as you believe I mine as well be telling you a fairytale right?

  14. Anonymous

    4:31 onwards …"beating up unsuspecting foreign loners". This explains why i got bullied all my life. Being an immigrant and a loner.

  15. Zebulon Virginia

    Sorry if I'm double commenting, I can't find my first comment. I said: Ugh, you talk too fast, I had to rewind a million times. I can't believe I'm subscribing… Thank you.

  16. kenan morani

    I was wondering what happened to all the medium generations from say Australopithecus to us human I mean what happened to those generations, have they all evolved into homo sepians and those all evolved to the next to lead all the way to modern humans. Shouldnt there be some other human like/Australopithecus like/Homo sepians like species around. What happened to those? and what is the evidence for their extinctions. ??

  17. Elmer Chica

    Lol. So your ancestor needed to run in the savanna thats why the started to walk. The only problem is that new adaptations dont just appear. It doesnt matter how much they needed to be able to walk.

Write a Comment

Your email address will not be published. Required fields are marked *