The Evolution Will Be Televised

A couple of quick thoughts on Nicholas Wade's fine article about the likelihood that human evolution is an ongoing process.

The article, a report on this paper in PLOS-Biology by Benjamin F. Voight, Sridhar Kudaravalli, Xiaoquan Wen, and Jonathan K. Pritchard, explains how their analysis of genetic variation in four populations found some 700 regions of the human genome that appear to have changed in response to selection pressure within the past 5,000-15,000 years.

My first thought was that this finding is a problem for evolutionary psychology -- at least in its mainstream version, as defined by John Tooby and Leda Cosmides, and popularized by my Matt Ridley and my former Sciences colleague Robert Wright, to name only two of the ablest advocates of this view.

High Church Ev Psych declares that human behavior was shaped by selfish-gene evolutionary pressures. The need to pass on your own genes and to secure good-quality genes in a mate is supposed to explain, for example, why men want younger women for mates, and why males are more prone to jealousy than females.

So why, you might ask, in some 25 percent of US hetero couples, is the woman the older partner? Or why, if the point of it all is to pass on genes, do society's best and brightest have fewer children than poor peasants?

The standard answer is that we did not evolve to live in today's society -- human behavior was shaped by the ``EEA,'' the ``environment of evolutionary adaptation.'' And that environment was the Pleistocene world of hunter-gatherer groups.

Now, if human evolution is an ongoing process, reflecting, as the PLOS-Biology authors say, possible adaptations for living as farmers rather than hunters, then there is no such thing as the environment of evolutionary adaptation. Or rather, we are living in it right now. So if people aren't doing what the ev-psychologist says they are driven to do, there can be no more saying ``well, you have to understand, people didn't evolve to live in modern London.'' It appears to be possible that they did.

Second thought: Wade favors the idea that our notions of race are based on true biological differences. (I don't quarrel with this, by the way. I just argue that there are many differences among human populations, and many ways that we can see ourselves, and therefore it's wrong to say race is more of a biological reality than other categories, like nation or temperament.) Anyway, Wade writes: ``The selected genes turned out to be quite different from one racial group to another. Dr. Pritchard's test identified 206 regions of the genome that are under selection in the Yorubans, 185 regions in East Asians and 188 in Europeans.''

Sounds like good evidence for important racial differences. But hang on a second. Were the Yorubans compared to other black people? Were the ``Europeans'' in the sample compared to another European population? Not that Wade mentions, and I can't find a reference to such a control in the paper itself. So while we've learned of differences between Europeans and Africans, we haven't been told how that compares to differences within each ``race.''

Which left me wondering: Who defined these races? Not the researchers, apparently. They are part of the ``HapMap Project,'' which studies differences in the variant genes of different populations (such genes travel in clusters called haplotypes; hence ``HapMap''). Haplotypes are associated with populations, not with races.

As Wade explains, ``the four populations analyzed in the HapMap project are the Yoruba of Nigeria, Han Chinese from Beijing, Japanese from Tokyo and a French collection of Utah families of European descent. The populations are assumed to be typical of sub-Saharan Africa, East Asia and Europe, but the representation, though presumably good enough for medical studies, may not be exact.'' (Emphasis added.)

In other words, we can be sure of sharp differences in the genes of these groups (and, I gather, of similarity in the Chinese and Japanese genes). But the idea that these particular populations represent vast races is assumed, and may not be exact.