Mutants!

Suppose there were a mutation that gave its possessor an extra 5% chance of surviving to reproduce (which is an enormous edge), and suppose that mutation were present in 1% of the gene sites 2000 years ago. Then today that mutation would be present in 33% of gene sites.

Because we have long generations, human evolution happens slowly when compared to historical time. Yet neither Nicholas Wade nor Jonathan Pritchard nor Gregory Cochrane seem capable of doing even the simplest of math. Julius Caesar was only 40 generations ago. The only thing that seems likely to be true in this article is the story of lactose-tolerance:

The Twists and Turns of History, and of DNA - New York Times: By NICHOLAS WADE: 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.

It is easy to imagine that in societies where trust pays off, generation after generation, the more trusting individuals would have more progeny and the oxytocin-promoting genes would become more common in the population. If conditions should then change, and the society be engulfed by strife and civil warfare for generations, oxytocin levels might fall as the paranoid produced more progeny....

Since the agricultural revolution, humans have to a large extent created their own environment. But that does not mean the genome has ceased to evolve. The genome can respond to cultural practices as well as to any other kind of change. Northern Europeans, for instance, are known to have responded genetically to the drinking of cow's milk, a practice that began in the Funnel Beaker Culture which thrived 6,000 to 5,000 years ago. They developed lactose tolerance, the unusual ability to digest lactose in adulthood. The gene, which shows up in Dr. Pritchard's test, is almost universal among people of Holland and Sweden who live in the region of the former Funnel Beaker culture.

The most recent example of a society's possible genetic response to its circumstances is one advanced by Dr. Cochran and Henry Harpending, an anthropologist at the University of Utah. In an article last year they argued that the unusual pattern of genetic diseases found among Ashkenazi Jews (those of Central and Eastern Europe) was a response to the demands for increased intelligence imposed when Jews were largely confined to the intellectually demanding professions of money lending and tax farming. Though this period lasted only from 900 A.D. to about 1700, it was long enough, the two scientists argue, for natural selection to favor any variant gene that enhanced cognitive ability....