Rice and genes and human evolution

Nicholas Wade:

EAST ASIAN and European cultures have long been very different, Richard E. Nisbett argued in his recent book "The Geography of Thought." East Asians tend to be more interdependent than the individualists of the West, which he attributed to the social constraints and central control handed down as part of the rice-farming techniques Asians have practiced for thousands of years.

A separate explanation for such long-lasting character traits may be emerging from the human genome. 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.

Trying to explain cultural traits is, of course, a sensitive issue. The descriptions of national character common in the works of 19th-century historians were based on little more than prejudice. Together with unfounded notions of racial superiority they lent support to disastrous policies.

But like phrenology, a wrong idea that held a basic truth (the brain's functions are indeed localized), the concept of national character could turn out to be not entirely baseless, at least when applied to societies shaped by specific evolutionary 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.

I'm sure this study will get a lot of favorable publicity

Important New York Times think piece on

Migration and evolution

Human Genome Still Evolving

Come out of that cave and see how much things have changed