An interview with Nicholas Wade
Humans are still evolving, says Nicholas Wade, still adapting to their environment. For years, scientists and social scientists have been wary of research on the evolution of modern humans, worrying that it would be used for malign purposes. But Wade, a science writer for the New York Times, argues that despite the threat of pseudoscientific theories about race and human nature, it's important to study how humans have continued to evolve over the past 50,000 years.
In his new book, Before the Dawn: Recovering the Lost History of Our Ancestors (Penguin, 2006), Wade uses recent findings in genetics, archaeology and linguistics to trace the history of Homo sapiens from the small group that took the first steps out of Africa to today's complex societies. He discusses the development of language, the change from nomadic to sedentary societies and other important milestones in our species' history. According to Wade, it only makes sense that humans would have continued to evolve, because they faced different challenges on each continent. American Scientist assistant book review editor Amos Esty spoke with Wade in April 2006.
What interested you in the broad topic of human evolution?
It was in the course of writing up genetics papers, which is what I do at the paper [the New York Times]. Many of them were related to aspects of the human past, and I began to see, firstly, how much of the past other disciplines had managed to cover—more than I was aware of—and, secondly, how genetics seems to be a new thread by which one could make a synthesis of all the information that is out there. That's what I tried to do in the book.
Was it difficult to put all these fields together into one narrative? What did you do when you found conflicting answers in different disciplines?
Well, it was a little difficult to put them all together. But I think in a way that's the most useful thing for a reporter to do, because you'll never know more about a field than the specialists, but you can usually try to cut across fields in a way that the specialists themselves do not usually do. So it seems to be an interesting challenge to try to weave all these seven or eight different fields together and share how much you could extract from the distant human past and show how [modern] humans are a part of the tree of human evolution. I think many people think that there's us and then there's the rest of the world, to which evolution applies. But the new findings make clear how much of our everyday life has its roots in evolutionary processes.
That's one of the main points that you make, that humans didn't stop evolving 50,000 years ago or 10,000 years ago. Why was it accepted for so long that human evolution just sort of stopped thousands of years ago?
That's a very interesting question. I think probably for a number of political reasons. It was just more convenient from many disciplines' point of view to assume that evolution was something they had no need to bother about, so almost all the social sciences—psychology, anthropology—have very little to say about evolution, which is odd if you believe that evolution should be the basic theory of everything to do with human activity.
It wasn't until we sequenced the genome that there was the genetic evidence to force reevaluation of the view that evolution stopped in the distant past. It's only now that you have the actual sequences and can follow the evolution of genes that you can see in one case after another that we have continued to evolve since the dispersal from Africa.
Did you find that in fields such as anthropology and archaeology there is still a lot of resistance to the idea that humans are still evolving?
I think it will begin to fade away, but it's still a bit novel to have incorporated itself into the worldview of these disciplines. For example, it's bizarre, when you think of it, that people who wish to understand psychology in evolutionary terms need to call themselves "evolutionary psychologists." It's as if you have one group of chemists who believe in the table of elements and another that didn't—the first don't have to call themselves Mendeleevian chemists.
A related topic that you talk about is the idea of race and how it is often thought of as just a social construct. You argue against that. Why?
Well, I think the subject of race has been so difficult and so polluted by malign ideas that most people have just left it alone, including geneticists. Geneticists have gone along with the position of the social sciences that race is not a biological concept, which I must say I find very hard to understand.
Geneticists are now beginning to change their minds because there is a good reason to look at the genetics of race, and it comes from medicine. It seems that each race or ethnic group has its own slightly different genetic basis for disease, so you need to know about that to tailor specific drugs for each ethnic group. In the course of looking at such genes and in the course of doing population history, it just becomes very clear that there are genetic differences between races, and particularly in selected genes. Most genetic variation is neutral—it doesn't do anything for or against the phenotype, and evolution ignores it—so most previous attempts to look at race have concluded that there's little difference between races. I think this position is the one on which the social scientists are basing their position.
But those surveys have looked at common variation, which is almost by definition neutral variation. If you look at the genes that do make a difference, selected genes, which are a tiny handful of the whole, you do find a number of differences, not very many, but a number of interesting differences between races as to which genes have been selected. This, of course, makes a lot of sense, because once the human family dispersed from its homeland in Africa, people faced different environments on each continent, different climates, different evolutionary challenges, and each group adapted to its environment in its own way. So it's hardly surprising that some differences would have arisen, and of course we can see the result in the fact that each race looks slightly different from the others.
It seems that the problem might be, as you said, that there is so much historical baggage associated with the term race. Is there a way to get around that? Do we just need a different term than race to talk about these genetic differences?
I'm not sure how that will play out. The geneticists, if you read their papers, have long been using code words. They sort of dropped the term "race" about 1980 or earlier, and instead you see code words like "population" or "population structure." Now that they're able to define race in genetic terms they tend to use other words, like "continental groups" or "continent of origin," which does, indeed, correspond to the everyday conception of race. When I'm writing I prefer to use the word race because that's the word that everyone understands. It's a word with baggage, but it's not necessarily a malign word. It all depends on the context in which it's used, I guess.
You discuss how, even though modern humans were around in Africa by 50,000 years ago, it wasn't until about 15,000 years ago that they began settling down and giving up their nomadic way of life. Why did it take 35,000 years for sedentism to develop?
That's long been one of the paradoxes of archaeology. What I suggest in my book is that a genetic change was required in order to make it possible for people to settle down. Genetic changes take some time to evolve, and just as the earlier big genetic change—the development of language, 50,000 years ago—emerged very recently, I think settling down was the second recent major evolutionary stride. The change, presumably, was to become less aggressive, to be able to settle down in fixed communities, in large enough groups to defend the settlement against other hunters and gatherers.
One piece of evidence comes from paleoanthropology: the thinning of human skulls that seems to have taken place at about the same time. The earlier human skills are very thick, what archaeologists call robust, and then there's a thinning of the skull and the skeleton that takes place between 50,000 to 15,000 years ago. The skulls become more gracile, as if human beings were being domesticated, and this is exactly the sort of change that takes place in the skulls of animals when they're domesticated.
How would that have worked on the ground? It seems that the first human to evolve a thinner skull would, in a nomadic society, have been at an evolutionary disadvantage.
I think it's very hard for us to say at present. We can see the trajectory of human evolution, and with luck we'll be able to pinpoint when each gene changed, but many of these most essential genes may have been involved in our social behavior. Presumably we used to live in rather small tribes, about 150 members, not more, which split up as members became less related to one another, because the basis of their association was kinship. Modern societies have taken a step beyond kinship. Our contemporary societies are far larger, and we live in a world of strangers whom we trust to an amazing degree in many contexts. I assume that change in behavior has a genetic basis, so something has made us more trusting in each other and therefore able to live in larger societies. If some mutation happened that made early people more trusting of each other and able to live in larger societies, that might have given them an advantage over tribes living in smaller numbers.
Has human culture gotten to the point where it supersedes biology to some point?
I think our culture is so strong and vivid that it has blinded us to the evolutionary underpinnings of society.
So, for example, you write that altruism is difficult to explain in evolutionary terms, but you can certainly find examples of it in human society.
Well, altruism is a basic behavior that is required of any social behavior. Presumably we developed altruistic behavior very early in our evolution, as primates, and if you look at the way chimpanzee societies or bonobo societies are organized, they all seem to be following a definite genetic template. So if you argue that there's a set of genes that shape social behavior that the chimps and the bonobos inherit from their ancestors, then we, too, must have inherited a version of that template, and I see no reason why it should have disappeared in present-day society. It has simply adapted as you would expect any other gene to adapt.
Within that template, in my view, must be embedded genes that shape our behavior, our propensities for aggression, religion, trade, conciliation, altruism—and all these forces must still be acting on our behavior. I think archaeologists have maybe done us a disservice by presenting the past as if it were peaceful and the present as if it were very warlike, because they've feared sending the wrong political message if they suggested that anything about our aggressive behavior today was justifiable. But in doing so they sort of blurred the message that we might have evolved considerably in terms of peaceful tendencies since our earliest ancestors.
Along those lines, you write about the major developments that made human society possible, such as trade, language, religion, the rise of the nuclear family. It sounds like you're saying that, in evolutionary terms, the ideal human society would be religious, capitalist, and monolingual, and would promote nuclear families. Should we be taking evolutionary theory into consideration in making policy decisions?
No, I think it's a fallacy to assume that our moral or political principles should be founded on what happens in nature. Many things happen in nature, such as incest or cannibalism, that we abhor. So we shouldn't draw our principles from what happens in nature. We should base our principles on the type of society we wish to live in. But that said, one shouldn't frame those principles in total divorce from evolutionary reality. You could argue that this is where Marxism went wrong—it assumed there was a perfect man, but by ignoring human nature and the desire for property and other things, it created a society that was impossible for people to live in happily.
How do we know when something really is part of "human nature"? Do we have to find genetic evidence?
Certainly genetic evidence is the best possible evidence for saying something is part of human nature, and this is why the subject is so difficult, because we're only just beginning to identify genes that influence behavior in lower animals, and our own behavior is much more complex. So we shouldn't expect the answer to be easy. Very rarely would we expect to find a single gene influencing a single behavior in humans. There's probably a whole set of genes, and it's very difficult for us to identify them. But I think when we do, that will be the best possible evidence for saying which of human behaviors have a genetic component and which do not.
Evolution, of course, doesn't intend to take us anywhere, but you do talk about the idea of evolutionary progress and say, for example, that even if scientific research casts doubt on the idea of humans having free will, we should continue our research or else it would be a "retreat into darkness." So it does sound like you think we might be advancing toward something.
I think if you look back at the sweep of human history, from 20,000 years ago, say, to today, I think most people would say, well, that's certainly progress. It's far better to live in the kind of society we have right now than to be a hunter and gatherer leading a precarious and harsh existence.
So how can one embed that perception of progress into evolutionary theory? Well, as you say, evolution has no goal, and progress is not part of the vocabulary of evolutionary biology. It seems to me that the escape from this dilemma lies in the fact that, firstly, the human genome responds to its environment—and the most important part of one's environment is the human society in which one lives. So people adapt genetically to the type of society they're living in. The best example of that, though it's not a behavioral change, is the development of lactose tolerance among European societies that depended on cattle.
If people respond genetically to society, then it follows that society feeds back into the genome. So if people choose to live in one kind of society rather than another, if they choose a society where conciliators and traders and intellectuals, say, are able to prosper and have more children than warriors do, then you can see how it might be possible in evolutionary terms for a more peaceful society to evolve. So this could be a way in which human choice has fed into the human genome and created a more desirable society over the course of millennia. And that is why it seems to us that there has been a storyline of progress.
Finally, in all the research you did for your book, is there anything that really surprised you?
I guess what surprised me is that, as far as I know, no one had put all these things together before. Some archaeologists, such as Colin Renfrew, have called for a grand synthesis of archaeology, genetics and historical linguistics, but that's sort of a dream that hasn't come to reality.
The other thing is that the more I dug, the more I found was there. It's amazing how much of these 50,000 years, most of which are entirely sort of blank pages, you can start to fill in a few details on.