Evolving Thoughts

Evolution, culture, philosophy and chocolate! John Wilkins' continuing struggle to come to terms with impermanence... "Humanus sum, nihil humanum a me alienum puto" - Terence

Sunday, April 23, 2006

Some more on race

Razib at Gene Expression has responded to my comments, and the original author Mike McIntosh, has updated his original piece with a few comments in response also. Good for both of them - I am not an expert in this matter, and I need the education. But first, let me deal with a few misunderstandings of what I said brought about by my execrable abuse of the English language (hey, I'm an Australian, and a philosopher. It's a wonder I have any readers at all).

Razib says of my comment:
Within-species groupings are, evolutionarily speaking, ephemeral. Ten thousand years ago, almost none of the non-African races existed. Ten thousand years from now, almost none of the modern races will continue to exist, I warrant.
First, I don't agree that "ten thousand years ago" there weren't any non-African races. Europe was settled for about 40,000 years by anatomically modern humans, Australia for 50,000 years, west and south Asia for somewhat longer, and the New World had just been settled. There has been a lot of time for human variation to evolve.
I was unclear. By this I meant that the categories we now call "races" for non-African populations - Caucasian, Asian, Austronesian, Amerind, and so forth, did not apply to populations outside Africa ten thousand years ago. Of course there were humans of variant kinds outside Africa. But take a case I know a little - the Australian aborigines. Work done by Alan Thorne on the Mungo Man skeleton in Australia and other work suggests that there were three or more migrations into the continent, one of which was more robust than the others. These date back at least 45kya. Given the variation in morphology of these migration waves, it looks pretty clear that "Australian" is a temporary class. More recent introgressive mating, from Javanese fishermen over at least a thousand years, and the rest of the ethnic world in the past 200 years, will leave the class even more changed in ten thousand years. I am claiming that the racial categories of modern use are ephemeral, not that there was no variation outside Africa.

Next, he said of my comment
The human species (convention makes me want to type "human race") is massively interbreeding.
How do you define massively? In Brazil peoples from various geographical "races" (just replace with "subpopulation" or something if you prefer) admix. In China this does not occur. Of course alleles spread, but they spread via selection as much as neutral processes, and that selection is often contingent on local conditions.

I define "massively" here as being continuous between populations on an evolutionary time scale. There are few (I know only of one. the Tasmanians) populations that are [were] not interconnected with others by gene flow. Perhaps there may be some in Papua or the Amazon. Even the !Mbuti, I am told, occasionally interbreed outside their group. In other species, the record is wildly variable, ranging from constant interbreeding and introgression between species, to almost zero if not zero interbreeding between populations of the same species isolated for millions of years. But humans have to be at the upper end of that scale.

There will be structure, of course But that structure will be limited to a local time scale, as they will be large scale tokogenetic networks similar to individual tokogeny. To be races, I would think that you'd need at the least to have long-term cladogenesis of the type found in haplotype groups of geographically isolated populations of other species. And I do not think that the Han group in China is free of interbreeding. Nor even is the caste structure in India so isolated from a biological perspective. Assortative matings don't make a race.

So, what does? It's a good question, and a hard one to answer. Razib notes that this is semantic; partly it is, partly not. There is a biological case as well. Typically, "race" is a well-defined subspecies in traditional taxonomy. We know there are subgroups in humans, so the question is whether there are sufficiently defined subgroups in humans. It's an empirical question. It's not, though, about alleles as such, but ensembles of alleles. There has to be a large number of alleles that are differentiated into clusters for there to be races. And I think the evidence is that there is not, at least, not that matches anything we call in social use "race". On the other hand I can often identify an African as being from the Afar, Yoruba or Maasai groups. The San are particularly identifiable. Perhaps they should be regarded as "races".

Razib says that there are functional allellic matching problems. Sure there are. This is what the whole research program is about. Is it race? Is it a "hillist-mountainist" problem as he says? Well yes. That's the problem with classification of evolutionary groups. One well-marked division is at the species level; that's why most of the time (exceptions of course, this is evolution) species are consensually accepted by biologists. And I fully concur with him that any taxonomic level is of the same "kind" as any other (see Nelson 1989), for all taxa are just lineages grouped by ancestry and division, and species are the same as any other clade, only with no permanent cladogenesis internally. Races, though, are not permanent (if they were, they'd be species in their own right).

So, given that there are genetic and phenotypic substructures, the only really significant dispute between us is whether the "folk taxonomy" categories match up to any biological reality. I think I'll stick with my claim that there isn't. There are clearly populations with differing clusters of features at the genetic and morphological level, and many of these are clearly the result of selection for local conditions. But would a Martian anthropologist identify our "races" as real races? I think not.

Matt's response is interesting. He makes the point that race is an abstractum, a point I made recently myself about other biological categories. And there is nothing wrong about abstracta - they are in fact necessary to scientific work. An abstraction can be a good representation of underlying causal realities. I merely disagree whether race is such an abstraction. By this I stress that I mean the usual categories used in the self-identification study. If you want to agree that the 54 categories of the Rosenberg study are races, then I have no objection. At least that gives us an empirical basis for cross-comparison. Eppur si muove indeed. But what moves here are not the races of the initial study.

Thanks to both Matt and Razib for their criticism.

Nelson, Gareth J. (1989), "Species and taxa: speciation and evolution", in D Otte and J Endler (eds.), Speciation and its consequences, Sunderland, Mass.: Sinauer.