Audio:
How Culture Drove Human Evolution
A Conversation with Joseph Henrich [9.4.12]
Beyond Edge
- Joe Henrich Homepage
- Culture, Cognition, & CoEvolution Lab
- Centre for Human Evolution, Cognition, and Culture
HOW CULTURE DROVE HUMAN EVOLUTION
A Conversation with Joseph Henrich [9.4.12]
Part of my program of research is to convince people that they should stop distinguishing cultural and biological evolution as separate in that way. We want to think of it all as biological evolution.
JOSEPH HENRICH is an anthropologist and Professor of Psychology and Economics. He is the Canada Research Chair in Culture, Cognition and Coevolution at University of British Columbia.
[39:00 minutes]
[ED. NOTE: This conversation with Joe Henrich was conducted in Vancouver for Edge by Jennifer Jacquet.]
HOW CULTURE DROVE HUMAN EVOLUTION [JOSEPH HENRICH:] The main questions I've been asking myself over the last couple years are broadly about how culture drove human evolution. Think back to when humans first got the capacity for cumulative cultural evolution—and by this I mean the ability for ideas to accumulate over generations, to get an increasingly complex tool starting from something simple. One generation adds a few things to it, the next generation adds a few more things, and the next generation, until it's so complex that no one in the first generation could have invented it. This was a really important line in human evolution, and we've begun to pursue this idea called the cultural brain hypothesis—this is the idea that the real driver in the expansion of human brains was this growing cumulative body of cultural information, so that what our brains increasingly got good at was the ability to acquire information, store, process and retransmit this non genetic body of information.
We've begun to pursue this idea called the cultural brain hypothesis—the idea that the real driver in the expansion of human brains was this growing cumulative body of cultural information.
The two systems begin interacting over time, and the most important selection pressures over the course of human evolution are the things that culture creates—like tools. Compared to chimpanzees, we have high levels of manual dexterity. We're good at throwing objects. We can thread a needle. There are aspects of our brain that seem to be consistent with that as being an innate ability, but tools and artifacts (the kinds of things that one finds useful to throw or finds useful to manipulate) are themselves products of cultural evolution.
Another example here is fire and cooking. Richard Wrangham, for example, has argued that fire and cooking have been important selection pressures, but what often gets overlooked in understanding fire and cooking is that they're culturally transmitted—we're terrible at making fires actually. We have no innate fire-making ability. But once you got this idea for cooking and making fires to be culturally transmitted, then it created a whole new selection pressure that made our stomachs smaller, our teeth smaller, our gapes or holdings of our mouth smaller, it altered the length of our intestines. It had a whole bunch of downstream effects. Another area that we've worked on is social status. Early work on human status just took humans to have a kind of status that stems from non-human status. Chimps, other primates, have dominant status. The assumption for a long time was that status in humans was just a kind of human version of this dominant status, but if you apply this gene-culture co-evolutionary thinking, the idea that culture is one of the major selection pressures in human evolution, you come up with this idea that there might be a second kind of status. We call this status prestige.
This is the kind of status you get from being particularly knowledgeable or skilled in an area, and the reason it's a kind of status is because once animals, humans in this case, can learn from each other, they can possess resources. You have information resources that can be tapped, and then you want to isolate the members of your group who are most likely to have a lot of this resources, meaning a lot of the knowledge or information that could be useful to you in the future. This causes you to focus on those individuals, differentially attend to them, preferentially listen to them and give them deference in exchange for knowledge that you get back, for copying opportunities in the future.
From this we've argued that humans have two separate kinds of status, dominance and prestige, and these have quite different ethologies.
From this we've argued that humans have two separate kinds of status, dominance and prestige, and these have quite different ethologies. Dominance [ethology] is about physical posture, of size (large expanded chest the way you'd see in apes). Subordinates in dominance hierarchies are afraid. They back away. They look away, where as prestige hierarchies are quite the opposite. You're attracted to prestigious individuals. You want to be near them. You want to look at them, watch them, listen to them, and interact with them. We've done a bunch of experimental work here at UBC and shown that that pattern is consistent, and it leads to more imitation. There may be even specific hormonal profiles with the two kinds of status.
I've also been trying to think broadly, and some of the big questions are, exactly when did this body of cumulative cultural evolution get started? Lately I've been pursuing the idea that it may have started early: at the origins of the genus, 1.8 million years ago when Homo habilis or Homo erectus first begins to emerge in Africa. Typically, people thinking about human evolution have approached this as a two-part puzzle, as if there was a long period of genetic evolution until either 10,000 years ago or 40,000 years ago, depending on who you're reading, and then only after that did culture matter, and often little or no consideration given to a long period of interaction between genes and culture.
Of course, the evidence available in the Paleolithic record is pretty sparse, so another possibility is that it emerged about 800,000 years ago. One theoretical reason to think that that might be an important time to emerge is that there's theoretical models that show that culture, our ability to learn from others, is an adaptation to fluctuating environments. If you look at the paleo-climatic record, you can see that the environment starts to fluctuate a lot starting about 900,000 years ago and going to about six or five hundred thousand years ago.
This would have created a selection pressure for lots of cultural learning for lots of focusing on other members of your group, and taking advantage of that cumulative body of non-genetic knowledge.
If you look at the paleo-climatic record, you can see that the environment starts to fluctuate a lot starting about 900,000 years ago and going to about six or five hundred thousand years ago. This would have created a selection pressure for lots of cultural learning.
Another signature of cultural learning is regional differentiation and material culture, and you see that by about 400,000 years ago. So, you could have a kind of late emergence at 400,000 years ago. A middle guess would be 800,000 years ago based on the climate, and then the early guess would be, say, the origin of genus, 1.8 million years ago. Along these same lines, I've been trying to figure out what the ancestral ape would have looked like. We know that humans share a common ancestry with chimpanzees about five or six million years ago with chimpanzees and bonobos, and the question is, what kind of ape was that?
One possibility, and the typical assumption, is that the ape was more like a chimpanzee or a bonobo. But there's another possibility that it was a different kind of ape that we don't have in the modern world: a communal breeding ape that lives in family units rather than the kind of fission fusion you might see in chimpanzees, and that actually chimpanzees and bonobos took a separate turn, and that lineage eventually went to humans spurred off a whole bunch of different kinds of apes. In the Pliocene, we see lots of different kinds of apes in terms of different species of Australopithecus.
I'm just beginning to get into that, and I haven't gotten very far, but I do have this strong sense that we now have evidence to suggest that humans were communal breeders, so that we lived in family groups maybe somewhat similar to the way gorillas live in family groups, and that this is a much better environment for the evolution of capacities for culture than typical in the chimpanzee model, because for cultural learning to really take off, you need more than one model. You want a number of individuals in your social environment to be trying out different techniques—say different techniques for getting nuts or for finding food or for tracking animals. Then you need to pay attention to them so you can take advantage of the variation between them. If there's one member of your group who's doing it a little bit better, you preferentially learn from them, and then the next generation gets the best technique from the previous generation.
Other things I've been thinking about along these lines are just trying to think through all the different adaptations that would have resulted from this gene culture interaction. One thing that's been noted by a number of people is that humans are strangely good at long distance running. We seem to have long distance running adaptations. Our feet have a particular anatomy. We have sweat glands and we can run really far. Hunter-gatherers can chase down game by just running the antelope down until it collapses. We run marathons. We seem generally attracted to running, and the question is, how did we become such long distance runners?
We don't see this in other kinds of animals. We think if it was an obvious adaptation, we'd see it recurring through nature, but only humans have it. The secret is that humans who don't know how to track animals, can't run them down, so you need to have a large body of tracking knowledge that allows you to interpret spores and identify individual animals and track animals over long distances when you can't see the animal, and without that body of knowledge, we're not very good at running game down.
Read the whole lengthy article.There's an interaction between genes and culture. First you have to get the culturally transmitted knowledge about animal behavior and tracking and spore knowledge and the ability to identify individuals, which is something you need to practice, and only after that can you begin to take advantage of long distance running techniques and being able to run animals down. That's a potential source for figuring out the origins of capacities for culture, because to the degree that we have information about the anatomy of feet, we can use that to figure out when it started. The same idea follows from cooking and fire. Since we know that those are culturally transmitted now, when we begin to see evidence that that affected our anatomy, that gives us clues to the origins of our capacities for culture.
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