Saturday, June 30, 2007

Race returns as ancestry, this time with better brains from China

A few years ago race was on the ropes, but it's back and looking as though it will persist, though possibly with a new name. The base "genetic clusters" (races) are:
  • Africans
  • Australian aborigines
  • East Asians
  • American Indians
  • Caucasians (Europeans, Middle Easterners and people of the Indian subcontinent)
(The "genetic cluster" breakdown in the graphic that accompanies the article is incomplete, the above list was taken from the article)

Not only is race back, but so are race-specific mutations affecting brain development. DAB1 is said to be "Chinese only", but I suspect the researchers are using "Chinese" as a proxy for "east asian". Anyway, the mutation sounds suspiciously like an upgrade:
Humans Have Spread Globally, and Evolved Locally - New York Times

Another puzzle is presented by selected genes involved in brain function, which occur in different populations and could presumably be responses to behavioral challenges encountered since people left the ancestral homeland in Africa.

But some genes have more than one role, and some of these brain-related genes could have been selected for other properties.

Two years ago, Bruce Lahn, a geneticist at the University of Chicago, reported finding signatures of selection in two brain-related genes of a type known as microcephalins, because when mutated, people are born with very small brains. Two of the microcephalins had come under selection in Europeans and one in Chinese, Dr. Lahn reported.

He suggested that the selected forms of the gene had helped improved cognitive capacity and that many other genes, yet to be identified, would turn out to have done the same in these and other populations.

Neither microcephalin gene turned up in Dr. Pritchard’s or Dr. Williamson’s list of selected genes, and other researchers have disputed Dr. Lahn’s claims. Dr. Pritchard found that two other microcephalin genes were under selection, one in Africans and the other in Europeans and East Asians.

Even more strikingly, Dr. Williamson’s group reported that a version of a gene called DAB1 had become universal in Chinese but not in other populations. DAB1 is involved in organizing the layers of cells in the cerebral cortex, the site of higher cognitive functions.

Variants of two genes involved in hearing have become universal, one in Chinese, the other in Europeans...

... A genomic survey of world populations by Dr. Feldman, Noah Rosenberg and colleagues in 2002 showed that people clustered genetically on the basis of small differences in DNA into five groups that correspond to the five continent-based populations: Africans, Australian aborigines, East Asians, American Indians and Caucasians, a group that includes Europeans, Middle Easterners and people of the Indian subcontinent. The clusterings reflect “serial founder effects,” Dr. Feldman said, meaning that as people migrated around the world, each new population carried away just part of the genetic variation in the one it was derived from...

... The concept of race as having a biological basis is controversial, and most geneticists are reluctant to describe it that way. But some say the genetic clustering into continent-based groups does correspond roughly to the popular conception of racial groups....

... David Reich, a population geneticist at the Harvard Medical School, said that the term “race” was scientifically inexact and that he preferred “ancestry"...
Ethnicity reflects your cultural identity, so that word is clear enough. I think "ancestry" is too vague -- Japanese and Koreans may feel they have very different "ancestry" (and in a sense they do), but they're not two "races". I think we're stuck with race for now.

So what year will we start tweaking human brains with the "best" (heh, heh) upgrades? I'm guessing 2040, because it will probably be pretty hard to get right.

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