Why Human Evolution Matters: Crash Course Big History 204

Why Human Evolution Matters: Crash Course Big History 204

February 8, 2020 100 By Kailee Schamberger


Hi, I’m Emily Graslie, and welcome to Crash
Course Big History, where today we’ll be discussing a tweak in our evolutionary traits
that led us to innovate so rapidly in the last 250,000 years. Natural selection is no slouch at innovating. We’ve moved from a planet populated by single
cell organisms just 700 million years ago to all the wondrous multi-celled giants that
we see around us: mammals, birds, bivalves, insects and invertebrates, reptiles, amphibians,
plants, and it goes on. There have been millions upon millions of
species past and present. Yet natural selection requires death, extinction,
random variation and non-random selection to innovate. It is a process that takes an arduous amount
of time – small changes, generation after generation, and ultimately epoch after epoch. Mistakes and successes mount up over thousands,
millions, and billions of years. Cultural evolution, on the other hand, takes
innovation out of the hands of the more sluggish DNA and evolutionary instincts and into the
marketplace of ideas. Good ideas, bad ideas, can be tinkered with,
exploited, and improved within a single generation at rates that random variations in our DNA
cannot. Racing down the path of adaptation, instead
of a horse and cart on a dirt road, we are soaring ahead in a private jet, and higher
rates of complexity are the result. It’s a rise with no immediate end in sight. The Latin name for our species, Homo sapiens,
means “wise man” which is kind of an arrogant name to give yourself. But it isn’t just being “wise” that
has led to the massive rise of complexity in human societies over the past 250,000 years. In the last season of Crash Course Big History,
we covered “collective learning” — the ability of a species to accumulate more information
with each passing generation than is lost by the next. Eventually these innovations stack up. Homo sapiens went from stone tools to skyscrapers,
rather than living in the same ecosystems and living the same lifestyles as we did a
quarter of a million years ago. The history of rising human complexitIes involves
tinkering with some form of prior knowledge rather than spontaneous genius. Cultural evolution rarely makes leaps. The Rolex watch wasn’t invented overnight
when an early human spilled her dinner on a bear-skin blanket and it just so happened
to resemble the shape of a wristwatch. The Rolex was the result of centuries of tinkering
and slight improvements over generations. The higher the population, the more potential
innovators you have. Which is why things began to snowball after
the invention of agriculture, and even more after the Industrial Revolution in the 18th
and 19th centuries. Instead of small tribes of a few dozen, potential
innovators became groups of thousands, millions, and now billions. Not everybody in a human society thinks up
new ideas: some ideas are forgotten, and some people come up with bad ideas. The self-pedalling shower, for instance, or
hydrogen blimps like the Hindenburg, or mullets… these are all… not great ideas. But on a long enough time scale, every generation
you get a population of skilled inventors with new ideas. The good ideas that stick are remembered by
humans, perhaps set to writing, then adjusted and explored generation after generation,
and improved once again. As a result, you probably aren’t out carving
your own stone tools right now. You are watching me. Why humans evolved the capacity for collective
learning remains a mystery. But like all mysteries in history and evolutionary
biology, this one must be explored on the basis of the evidence. Basically, we wanna know, “What makes humans
different?”, at least in an evolutionary sense. The differences don’t just stem from our
adept use of communication. Plenty of animals communicate with each other. This might be done visually, like a male peacock
displaying its brightly coloured feathers as a courtship gesture. It might be a dog baring its teeth, as a sign
of aggression. It might be audible, like a gopher letting
out a warning squeak that a predator is nearby. It might be a smell, like ants communicating
through pheromones. It might even be something as intricate as
whale songs that carry over large distances. Here you have transmission of information,
but no steady accumulation generation after generation, thus no collective learning. And it’s not just because we’re exceptionally
good teachers. Sperm whales teach their calves the dialects
of their particular language: the specific clicks, moans, and frequencies. Meerkats that feed on scorpions demonstrate
how to carefully handle their venomous prey. Baboons teach each other more efficient ways
to hunt. And chimpanzees educate their young on how
to fish termites out of the ground for an afternoon snack. But still, there’s no tinkering, or improvement,
and no accumulation. Thus, it’s not collective learning. But the seeds of this communication and learning
were there for a long time in the evolutionary tree, since those traits are present in many
other species. At some point between our separation from
our last common ancestor with chimpanzees 5-7 million years ago, and the emergence of
Homo sapiens 250,000 years ago, evolution built up these skills for communication and
learning and allowed it to be stored in the collective memories of human groups. And while our big brains provide use with
very useful hardware, large brain sizes wouldn’t have evolved either, unless there was a very
specific evolutionary pressure for it. Brains need energy to run, and a big brain
needs a lot of energy. Gathering food takes time, effort, and even
increases our chances of risk. So there would have to be an evolutionary
incentive for it that outweighed the potential costs. The original increase in primate brain size
relative to body mass in the ancestors of monkeys and apes, was the need to process
3D visual information from when we were living in trees- mostly so we didn’t tumble down
to our deaths. Let’s go to the Thought Bubble. We also know that in all groups of primates,
brain power is needed to navigate their fairly complex social hierarchies and alliances. These hierarchies often determine access to
food, mates, and ultimately to the continual survival of an individual’s DNA. The higher you are in the hierarchy, the better
your evolutionary opportunities are. And it takes a lot of care to maintain your
place in such a hierarchy…. like in pre-modern aristocracies, modern politics,
celebrity circles, and, unfortunately, sometimes in high school. As such, skills at communication and learning,
along with the brain power to keep up with those social pressures, were useful neurological
traits to evolve. Chimpanzees, for instance, are able to communicate
a wide range of information and can even be taught to recognize quite a few symbols, on
par with a human toddler. But, their larynxes only allow them to vocalise
a limited range of sounds. This seems to have remained the case in the
early hominids Australopithecines and Homo habilis. There is even some debate whether even the
Neanderthals had more limitations on sound than humans. That said, much of primate communication is
done, like with many other animals, through gesticulation. And even today, gesture is a large part of
day-to-day human communication to convey information. Everything from moving your hands while you
talk, to a cheerful thumbs up, to more offensive hand gestures communicate meaning. There’s also your facial expressions and
your body posture, which aid in expression. Still, without language, our hominid ancestors
were able to communicate information, adapt to new environments, use tools, and travel
across the world. Thanks, Thought Bubble. Humans do communicate successfully with gestures-
but there’s a huge capacity for complex language and abstract thought as well. And at some point in our evolutionary history,
this went into overdrive. In order to solve this mystery, scientists
have assembled a gaggle of hypotheses that to this day are being evaluated by careful
scrutiny of the evidence. Perhaps complex human language evolved because
better communication between mothers and their offspring favoured the survival of infant
primates. So, maybe 3.5 million years ago when Australopithecus
became bipedal, mothers stopped carrying infants on their backs as often, like chimpanzees
do. Instead mothers would need another way to
look after their young when looking for food – like, talking in order to exchange information. “Are you in danger? Behave yourself! Stop throwing things at your brother.” Perhaps somewhere between the evolution of
Homo habilis 2.8 million years ago and Homo erectus 1.9 million years ago, groups got
bigger thanks to the use of their tools. And bigger groups meant the old ways of forming
alliances in most primates became more difficult. Namely, grooming. You can’t give everyone a haircut. Instead, another way of forming bonds emerged. There was gossip and banter- perhaps first
as sounds, then later evolving into more precise exchanges of information. This progression of complex ideas may come
down to our increasing consumption of meat. In some parts of East Africa for the past
few million years, vegetation may have at times been scarce. Our ancestors started scavenging more and
more meat from corpses. Meat packs more energy per bite than vegetables,
and this boost to our metabolisms might have increased brain size. Or maybe it’s as simple as when Homo habilis
and its descendants started using tools with their hands more frequently. They had to evolve stronger vocalizations
in order to communicate effectively hands-free. Yet another option is that advanced communication
may have evolved as a form of sexual selection. It is possible that hominine females preferred
mates that were capable of two things: either expressing themselves in a range of ways,
such that the male essentially “talked” their way into a relationship, and that females
may have preferred males that were able to both transmit and receive pertinent information
so they increased their chances of survival and their ability to provide for their young. But all of these hypotheses presume some sort
of environmental change that endangered the survival chances of our ancestors, making
these evolutionary traits grow stronger more rapidly. And indeed we know that the climate of Africa
was fluctuating very rapidly over the past 4 million years, meaning our ancestors had
to adapt faster in order to survive. Something must have made the benefits of operating
a larger and more flexible brain outweigh the costs of stocking up on food and keeping
it humming with energy. Afterall, natural selection doesn’t do anything
for free. When it comes to testing these theories, only
a limited amount of evidence can be yielded from fossils and discoveries of ancient toolkits. Those research endeavours in Africa have only
just scratched the surface. Another way of testing those theories is to
look at our evolutionary cousins today, particularly the great apes, in order to understand the
dominant and useful traits that may have been shared by our ancestors. It could be that all of the hypotheses we
covered are valid and were working under evolutionary pressures simultaneously. Or perhaps it’s something we haven’t considered
yet. The big question is, when did our capacity
for learning and communication begin to resemble collective learning? There’s evidence that Homo erectus, which
existed 1.9 million years ago, made small improvements to early tools, but that happened
over several hundred thousand years. There is significantly more evidence that
the species in between us and Homo erectus improved their technologies much more quickly. There’s very little doubt that the newcomer,
Homo sapiens, was really good at collective learning. But we aren’t even completely sure where
we fit with all these other species on the evolutionary tree. Were our immediate predecessors also very
gifted at collective learning? We won’t know until more digs are performed
and more discoveries are made. And it pushes back the genesis of collective
learning to a very special set of conditions and traits that existed 2 to 3 million years
ago. Like any history book, the pages of the grand
narrative are filled with blank spots that require more research, fact-finding, and interpretation. It would be very convenient if we had an existing
species or an extinct species in the fossil record with a similar degree of collective
learning to compare to humans. But it is possible that if such a species
had existed on Earth previously – dinosaurs building skyscrapers and sharing pictures
on Instagram – that there may not have been room for our species to enter the same evolutionary
niche. In the past 3.8 billion years of Earth’s
history, this sort of behaviour is unprecedented. We humans seem to have stumbled into it by
some mysterious quirk of natural selection. And until we’re able to observe our evolutionary
cousins a little more, the blank pages of human evolution will stay blank, awaiting
the day when another potential innovator tinkers, improves, and adds their own piece of collective
learning upon them. Thanks for watching, see you next time.