[extropy-chat] New Path For Evolutionary Psychology
lcorbin at tsoft.com
Sun Mar 19 02:43:31 UTC 2006
>From innate violent tendencies of the Yanomamo, to *trust*,
to the cognitive ability of Jews, it's a watershed event
when a mainstream publication like the NYT can print notions
that were complete anathema only a mere twenty years ago:
ADAPTATION By NICHOLAS WADE
Published in the New York Times: March 12, 2006
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
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
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
Napoleon Chagnon for many decades studied the Yanomamo, a warlike people who live
in the forests of Brazil and Venezuela. He found that men who had killed in
battle had three times as many children as those who had not. Since personality
is heritable, this would be a mechanism for Yanomamo nature to evolve and become
fiercer than usual.
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.
One theme in their argument is that the variant genes perform related roles,
which is unlikely to happen by chance since mutations hit the genome randomly. A
set of related mutations is often the mark of an evolutionary quick fix against
some sudden threat, like malaria. But the variant genes common among the
Ashkenazi do not protect against any known disease. In the Cochran and Harpending
thesis, the genes were a response to the demanding social niche into which
Ashkenazi Jews were forced and the nimbleness required to be useful to their
No one has yet tested the Cochran-Harpending thesis, which remains just an
interesting though well worked out conjecture. But one of its predictions is that
the same genes should be targets of selection in any other population where there
is a demand for greater cognitive skills. That demand might have well have arisen
among the first settled societies where people had to deal with the quite novel
concepts of surpluses, property, value and quantification. And indeed Dr.
Pritchard's team detected strong selection among East Asians in the region of the
gene that causes Gaucher's disease, one of the variant genes common among
Perhaps the time isn't far off when even in polite society
it will be possible to utter the dread "e-word".
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