Race: maybe it's agriculture

By Razib Khan | March 2, 2012 3:23 pm

I’m too busy to really blog today, but I thought of putting up a post, the gist of which was actually expressed in Ian’s comment below:

When I was younger, I thought of human races as archetypes, and the variation between them a product of mixing. I blame it on the fact that I read Coon when I was about 14. Still, as a (half)Indian, it’s hard to see reconcile the reality of a billion people in the subcontinent with models that try to classify people into 3-5 races. As I learned more biology, I came to the conclusion that human variation was clinal, and race was really an artefact of where you chose to sample along the continuum…as a plant ecologist, I think about things like that a lot. (I’m also somewhat skeptical of ecozones.)

Thanks to a number of convergent strands (of which Razib’s blogging has been a key element), I have come to a rather different conclusion. Race, in my opinion, is more a feature of agriculture than evolution.

Consider two possible models of race: Model 1, in which sharp distinctions existed before the Neolithic, and have been maintained and enhanced as certain groups adopted agriculture and displaced their hunter-gatherer neighbours; and Model 2, in which variation was clinal prior to the Neolithic, but that the immense demographic expansion of certain groups expanded THEIR specific points on the continuum, and brought them into contact (or nearly into contact) with other expansionist agriculturalists.

To me, the Model 2 seems more plausible than Model 1. Is that an argument against race? No, but it does suggest that races shouldn’t really be seen as “locally adapted optima” and rather, should be seen more as transient phenomena produced by historic contingency. Whether this means that race is “real” or not is, to me, a little beside the point. But I’m not convinced by Coyne’s argument that these differences represent the “accumulation of genetic differences between isolated populations”.


A hybrid?

Isolation-by-distance is a powerful null model. But if Reconstructing Indian History is correct then it is a poor description of the recent history of the Indian subcontinent. Since there are ~1.5 billion South Asians I think that that is a major objection. And I don’t think it is just South Asians. Even 10,000 years ago I suspect that a clinal isolation-by-distance model would be confronted by several clusters of demes which were operationally allopatric (e.g., West Eurasia & North Africa vs. East Eurasia, Austarlasia, the New World, Sub-Saharan Africa, and likely South Asia). This probably had to do with the fact that human occupation is not, and was not, evenly distributed.

Image credit: Wikipedia

CATEGORIZED UNDER: Human Genetics
MORE ABOUT: Race
  • Ezequiel Martin Camara

    My view would be that reality is more complicated that any of these models. A constant difusion mixes everything and builds the clinal landscape. All the while, power-law-scattered events cause regions of the landscape to expand and overtake neighbours. That creates the perception of borders and homogeneity. The fact that the distribution of people is not even, and that people tend to mix with like, adds to the perception. But it is all a transient situation that will continue to evolve. The Neolitic expansion is probably the largest event, but I am sure that there were many before and after, at many different scales.

  • doc

    Civilization is the worst thing to befall man.

    Damn agriculture, damn it all to hell!

  • jb

    It seems to me that, in the limit, Models 1 & 2 are the same. If the demographic expansion of widely separated groups is sufficiently great, then it really doesn’t matter if those groups were genuinely isolated, or if they were originally part of a continuous population that showed clinal variation, because any intermediate populations which did not take part in the expansion end up being totally overwhelmed, and might as well never have existed.

    I do think it’s quite interesting that Coon & co., just by eyeballing it, managed to come up with races that match up reasonably well with modern genetic cluster analysis!

  • http://www.isteve.blogspot Steve Sailer

    Or maybe India is the center of the world and Europe, East Asia, Australia, and sub-Saharan Africa are outlying lobes?

  • http://www.isteve.blogspot Steve Sailer

    The isolation-by-distance model works pretty well if you count oceans, which often get overlooked.

  • http://www.isteve.blogspot Steve Sailer

    In general, I think the species model can be misleading because it encourages people to think of racial groups as archetypes. I don’t think the archetypal system is even hugely true for non-human animals. The species concept is an approximation applied to the confusion of nature.

    When we have more direct information about genealogy, we don’t worry about fitting creatures into categories based on looks as much. For example, consider racehorses. They are seldom categorized by coat color because we know their entire genealogy for over two centuries. To be a thoroughbred, you have to be descended thoroughly from 3 Arabian stallions and 20 English mares. You don’t have to be a particular color. You don’t even have to be terribly fast. (I know, I’ve bet on some.) We say that Seabiscuit is the grandson of Man o’ War and nephew of his own rival War Admiral, because we have their papers.

    Thoroughbreds are an extreme example of an inbred extended family, but human racial groups tend to be more moderately inbred extended families. We are all familiar with extended families, and are not baffled by the conundrums put forward about race when thinking about extended families. For example, how can people belong to more than one extended family? Well, how can they not?

  • http://dispatchesfromturtleisland.blogspot.com ohwilleke

    Sequentially, one would imagine that there was first Model 1, which took pretty great distances and long time periods to be noticeable, and then Model 2 took over and has dominated since except in environments where selective pressures are intense and atypical for the source population (e.g. Tibet).

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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