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On structure, variation, and race

I noticed yesterday that Andrew Sullivan, Ta-Nehisi Coates, and a cast of others were having a roiling debate on race and I.Q. My name came up in several comment threads on various issues. I’m aware of this because I have Google Alerts set for my name. I don’t have the time or energy to get immersed in this particular debate at this moment, but I did review some older material in the course of following links placed elsewhere. In particular, I encourage all of my newer readers to check out my friend Armand M. Leroi’s article in The New York Times from 2005, A Family Tree in Every Gene. Though dated in a few particulars (e.g., we know the locus responsible for most variation in blue eyes now, and it seems likely that Andaman Islanders and Malaysian Negritos are not the original settlers of their domains) I think the general outline has held up rather well. Compare it to the numerous vociferous responses over at SSRN. One wonders at the motivation for what seems like massive retaliation! Here are a few critical paragraphs from Armand’s piece:

The identification of racial origins is not a search for purity. The human species is irredeemably promiscuous. We have always seduced or coerced our neighbors even when they have a foreign look about them and we don’t understand a word. If Hispanics, for example, are composed of a recent and evolving blend of European, American Indian and African genes, then the Uighurs of Central Asia can be seen as a 3,000-year-old mix of West European and East Asian genes. Even homogenous groups like native Swedes bear the genetic imprint of successive nameless migrations.

Some critics believe that these ambiguities render the very notion of race worthless. I disagree. The physical topography of our world cannot be accurately described in words. To navigate it, you need a map with elevations, contour lines and reference grids. But it is hard to talk in numbers, and so we give the world’s more prominent features – the mountain ranges and plateaus and plains – names. We do so despite the inherent ambiguity of words. The Pennines of northern England are about one-tenth as high and long as the Himalayas, yet both are intelligibly described as mountain ranges.

So, too, it is with the genetic topography of our species. The billion or so of the world’s people of largely European descent have a set of genetic variants in common that are collectively rare in everyone else; they are a race. At a smaller scale, three million Basques do as well; so they are a race as well. Race is merely a shorthand that enables us to speak sensibly, though with no great precision, about genetic rather than cultural or political differences.

But it is a shorthand that seems to be needed. One of the more painful spectacles of modern science is that of human geneticists piously disavowing the existence of races even as they investigate the genetic relationships between “ethnic groups.” Given the problematic, even vicious, history of the word “race,” the use of euphemisms is understandable. But it hardly aids understanding, for the term “ethnic group” conflates all the possible ways in which people differ from each other.

The problem here is the word “race.” It has a whole lot of baggage. So many biologists prudently shift to “population” or “ethnic group.” I don’t much care either way. Let’s just put the semantic sugar to the side. I contend that:

1) Human populations can be easily separated into plausible clusters using a random set of genetic markers

2) The differences between human populations are not trivial

You can say that both positions apply to human races. Or, you can say that race does not exist as a biological concept, and that both positions apply to human populations. Call it what you will, style is secondary to substance. Just as half-siblings and full-siblings are clearly genetically distinct, and those distinctions matter in terms of their traits, so French and Chinese are genetically distinct, and those distinctions matter in terms of their traits.

In the mid-2000s Armand, and at the time myself as well, put a great deal of weight on the importance of the elucidation of population structure for biomedical purposes. How else is one going to get funded by the N.I.H.? At this point I’m not sure that that’s going to be the low hanging fruit in the near term. Rather, I think an understanding of the phylogeny of the human race is a grand story. Population structure in the present is a shadow of histories past. And with the possibility of admixture with archaic lineages and recent adaptations that story has a lot of novel plot elements to keep your attention.

COMMENTS NOTE: Any comment which misrepresents the material in this post will result in banning without warning. So you should probably stick to direct quotes in lieu of reformulations of what you perceive to be my intent in your own words. For example, if you start a sentence with “so what you’re trying to say….”, you’re probably going to get banned. I said what I tried or wanted to say in the post. Period.

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