Discover Dialogue: Evolutionary Biologist Mark Pagel

Human cultural groups have behaved as if they were different species

By Kathy A. Svitil|Sunday, May 01, 2005

Mark Pagel, a professor of evolutionary biology at the University of Reading in England, doesn’t consider himself a scientist, just a person thinking about the world. His musings traverse a diverse range of subjects—from baboon sexual displays to human hairlessness to the evolution of language. The common thread is his attempt to understand how natural selection has caused organisms, including humans, to become the way they are. Pagel helped pioneer the integration of mathematics and statistics with evolutionary studies. Recently, he and anthropologist Ruth Mace of University College London proposed the controversial idea that human cultural diversity can be understood by thinking of different cultures as if they were distinct biological species.

Why do you think few scientists have looked at human behavior through the lens of evolution and natural selection?

P: Humans like to think of themselves as unusual. We’ve got big brains that make it possible for us to think, and we think that we have free will and that our behavior can’t be described by some mechanistic set of theorems or ideas. But even in terms of much of our behavior, we really aren’t very different from other animals.

How so?

P: We are a species that has territories. We choose mates on the basis of characteristics that we think will be related to our success in reproducing. We produce offspring and invest in those offspring. We engage in warfare. We forage for food. There are many aspects of our behavior that are very similar to the behavior of animals.

We must be different in some way.

P: Where we depart is in our cultural behavior, which is also inherited but not biologically inherited. We have capabilities for rapidly evolving at a cultural level or developing cultural practices or beliefs or behaviors that other animals aren’t capable of. And in those ways, we depart. We also depart because we are intelligent—probably vastly more intelligent than any other animal on the planet, despite what people say about dolphins and elephants. That gives us a language, and that ability to communicate with each other at a symbolic level means that we can achieve things that other animals just can’t.

Is there anything you’ve learned about human behavior that surprises you?

P: What surprises me most about studying human behavior from an evolutionary perspective is that humans, despite being genetically quite homogeneous, nevertheless achieve a diversity of behaviors and cultural practices and languages that rivals anything on Earth. Human cultural diversity is vast; the range of cultural practices, beliefs, and languages that we speak is vast.

Why did humans diversify so much?

P: What drives the separation of groups of people into subgroups is the desire to control resources. We begin with a single culture, and over time the number of individuals within that culture expands. At some point, some of the individuals will say, “Well, if we banded together, we could garner some territory and we could make a go of it on our own.” Now we have two groups who are competing for the same resources. So they set up territories. In effect, they’re setting up fences and saying, “Don’t cross that.”

So the groups start to become different once the fences between them are up?

P: Those groups are free to diverge in their beliefs and their behavioral practices and so on. So I think the driving force for cultural evolution is this desire for groups to be splitting off and separating and forming subgroups insofar as the environment will allow it. We see great cultural diversity and large numbers of cultures per unit area in regions of the world in which the environment is really rich. In the tropics, for example, there’s a lot of biomass, so there’s a lot to eat and a lot to make shelters from.

That doesn’t seem surprising. An area with more resources can support more people.

P: It seems like a really obvious point, but the key question is: Why don’t the human beings in those areas just form one great big cooperative group? Why do they break into smaller groups? They must be subdividing for some good reason, and the good reason must be that the environment is rich enough for individuals to go it alone, so they don’t have to compromise their aspirations in any way to some other members of the group.

These days we are concerned about cultural homogenization—the loss of unique cultures as separate groups merge.

P: Prior to European contact, North America was probably divided up into at least 500 different cultural groups, and Australia was divided up into at least 500 to 600 distinct cultural groups. Now many of those groups have been lost, and so have groups in other areas too. So the current state is very different from how it was. One of the puzzling and fascinating things about humans is that we have the ability to form enormous groups—the United States, with 290 million people, or Britain, with 60 million people—that are led by very small numbers of individuals.

How does that fit with the idea that human groups subdivide to control resources? It seems like a contradiction.

P: I don’t think we really have an answer, except that in the large groupings that work, like Britain, America, and China, the need to subdivide the environment gets removed by an economy that provides you with the principal foodstuffs you need and a roof over your head. That might be why some nations are able to grow very large without special interest groups saying, “Hey, we’re not getting our share here” and trying to subdivide. With the collapse of the Soviet Union, you instantly saw 15 nation-states immediately arising, which means the Soviet Union wasn’t ever providing those people with what they wanted.

Humans have a need to explore, to search for and to find new territories. Is that a quest for more resources?

P: I think it is. Some animals are very good at leaving where they live and exploring other parts of the world—birds, for example, and rats. Rats are found all over the world. Evolutionary biologists call these species supertramps. The ultimate supertramp species is obviously humans. Just like any other animal that leaves where it lives and goes somewhere else, we’re looking for a better life.

Doesn’t that make the separation between cultures flimsy, with people crossing borders and integrating themselves into new groups as they move around?

P: Yes, but we don’t do it as much as we could. We have the capacity to scramble up all the cultures every generation. We can all interbreed, and we can all eat the same food. So there’s no reason why we should maintain all this separation. Yet we do. What is fascinating about human cultures is that despite every opportunity for us to be swamped by the cultures around us, somehow the cultures are quite strong, as if deflecting the cultures around them.

You’ve said that one implication of cultural separation is that we have an innate wariness of strangers.

P: People have seized on that as a statement of jingoism or bigotry, but we’re trying to understand how you get the patterns of cultural diversity that you really do get. Human cultural groups have behaved as if they were different species that actively exclude each other, and cultures do have a wariness of strangers. I think it may be a deep-seated part of our psychological makeup. It isn’t necessarily something that we want to promote or be proud of, but it is something that we ought to be aware of.

If different culture groups keep to themselves and reinforce barriers, why are humans still so genetically similar?

P: We’re a very young species. We may all descend from a very small number of individuals who lived somewhere between 100,000 and 300,000 years ago. We’re really just getting out of the starting blocks—this may explain why we’re so bad at being what we are—so there hasn’t been enough time for us really to diverge genetically.

Will we?

P: It’s tempting to speculate that we were on the road to evolving into separate species. There’s absolutely no reason to rule it out. We never got that far. Instead, we were so good at developing mass transport and communication and moving around the world that now we are sharing genes at a high enough level that we will homogenize more.

Is this mixing why we’re losing languages?

P: We’re losing languages because there are a few languages that are associated with cultures that are economically and politically dominant, so everybody starts speaking them. But another reason we’re losing languages is that the more people mix, the more they’ve got to agree on how they’re going to talk to each other. That necessarily means some of the languages have got to go.

You’ve said that the loss of languages will lead to the loss of unique ways of thinking.

P: Nobody’s language has forced them to believe that the world is flat or that something like gravity doesn’t exist, but there are much subtler ways in which language, as an expression of culture, may structure the way we think. Japanese infants discriminate the r sound from the l sound, but Japanese adults have trouble making the discrimination. It’s an actual physical alteration to the brain. There will be other discriminations that you and I cannot make that speakers of other languages can make. If that’s the case, if language can structure the brain at those levels, maybe language in its association with culture makes us think about the world in different dimensions. If we lose languages, those ways of thinking will also be lost.

Would that explain how cultural differences might be reinforced?

P: Yes, it may help explain why one is always more comfortable moving through natal language and culture than in an adopted language or culture.

As cultures merge and we homogenize, will we all start to look the same?

P: I would say we probably will.

How long will it take?

P: I don’t think anybody knows. If you mix people up enough, and there is sufficiently limited choice, you’ll get people mating with one another and crossing these kinds of sexually selective bounds. But as long as there is cultural choice and financial choice and economic choice, the change will be slow.

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