Sunday, March 12, 2006

Still evolving commotion

More from Nicholas Wade of the Times on the evidence that numerous human genes have been under selection pressure during historical (5-10k year) timescales. (See earlier post here.) The results imply that human populations as recently as a few thousand years ago might have had very different allele frequencies than current populations. (For example, a mutation present at the 1% level then might have become commonplace today.) The implications for history and society are fascinating. Note that different sets of genes have been under selection in different regions of the world -- leading to uncomfortable questions concerning group differences.

For the flabbergasted, ill-reasoned, politically-correct reaction, see Brad DeLong.

NYTimes: ...Humans have continued to evolve throughout prehistory and perhaps to the present day, according to a new analysis of the genome reported last week by Jonathan Pritchard, a population geneticist at the University of Chicago. So human nature may have evolved as well.

If so, scientists and historians say, a fresh look at history may be in order. Evolutionary changes in the genome could help explain cultural traits that last over many generations as societies adapted to different local pressures.

...In a study of East Asians, Europeans and Africans, Dr. Pritchard and his colleagues found 700 regions of the genome where genes appear to have been reshaped by natural selection in recent times. In East Asians, the average date of these selection events is 6,600 years ago.

Many of the reshaped genes are involved in taste, smell or digestion, suggesting that East Asians experienced some wrenching change in diet. Since the genetic changes occurred around the time that rice farming took hold, they may mark people's adaptation to a historical event, the beginning of the Neolithic revolution as societies switched from wild to cultivated foods.

Some of the genes are active in the brain and, although their role is not known, may have affected behavior. So perhaps the brain gene changes seen by Dr. Pritchard in East Asians have some connection with the psychological traits described by Dr. Nisbett.

Some geneticists believe the variations they are seeing in the human genome are so recent that they may help explain historical processes. "Since it looks like there has been significant evolutionary change over historical time, we're going to have to rewrite every history book ever written," said Gregory Cochran, a population geneticist at the University of Utah. "The distribution of genes influencing relevant psychological traits must have been different in Rome than it is today," he added. "The past is not just another country but an entirely different kind of people."

John McNeill, a historian at Georgetown University, said that "it should be no surprise to anyone that human nature is not a constant" and that selective pressures have probably been stronger in the last 10,000 years than at any other epoch in human evolution. Genetic information could therefore have a lot to contribute, although only a minority of historians might make use of it, he said.

The political scientist Francis Fukuyama has distinguished between high-trust and low-trust societies, arguing that trust is a basis for prosperity. Since his 1995 book on the subject, researchers have found that oxytocin, a chemical active in the brain, increases the level of trust, at least in psychological experiments. Oxytocin levels are known to be under genetic control in other mammals like voles.

1 comment:

Anonymous said...

Apropos, from the politically correct Steve Levitt:

I wonder what sort of natural selection criterion would lead to stupider asian babies who then become smarter later in life?

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