Thursday, February 12, 2009

Part Three

Darwin resisted writing about the evolution of man but eventually relented and in 1871 published a book The Decent of Man and Selection in Relation to Sex. He made the right guess by suggesting that man evolved in Africa.Explorers returning from Africa brought back gorillas and chimpanzees which showed that they were more like humans than orangutans were.Darwin was able to show that humans had evolved from apelike ancestors. This was a great leap forward considering that he did not have the evidence that we have available to us now. There were no stone tools or fossils for him to examine

"It's an old-fashioned, even Victorian, sentiment. Who speaks of "racial
stocks" anymore? After all, to do so would be to speak of something
that many scientists and scholars say does not exist. If modern
anthropologists mention the concept of race, it is invariably only to
warn against and dismiss it. Likewise many geneticists. "Race is social
concept, not a scientific one," according to Dr. Craig Venter - and he
should know, since he was first to sequence the human genome. The idea
that human races are only social constructs has been the consensus for
at least 30 years. But now, perhaps, that is about to change. Last
fall, the prestigious journal Nature Genetics devoted a large
supplement to the question of whether human races exist and, if so,
what they mean. The journal did this in part because various American
health agencies are making race an important part of their policies to
best protect the public - often over the protests of scientists. In the
supplement, some two dozen geneticists offered their views. Beneath the
jargon, cautious phrases and academic courtesies, one thing was clear:
the consensus about social constructs was unraveling. Some even argued
that, looked at the right way, genetic data show that races clearly do
exist. The dominance of the social construct theory can be traced to a
1972 article by Dr. Richard Lewontin, a Harvard geneticist, who wrote
that most human genetic variation can be found within any given "race."
If one looked at genes rather than faces, he claimed, the difference
between an African and a European would be scarcely greater than the
difference between any two Europeans. A few years later he wrote that
the continued popularity of race as an idea was an "indication of the
power of socioeconomically based ideology over the supposed objectivity
of knowledge." Most scientists are thoughtful, liberal-minded and
socially aware people. It was just what they wanted to hear. Three
decades later, it seems that Dr. Lewontin's facts were correct, and
have been abundantly confirmed by ever better techniques of detecting
genetic variety. His reasoning, however, was wrong. His error was an
elementary one, but such was the appeal of his argument that it was
only a couple of years ago that a Cambridge University statistician, A.
W. F. Edwards, put his finger on it. The error is easily illustrated.
If one were asked to judge the ancestry of 100 New Yorkers, one could
look at the color of their skin. That would do much to single out the
Europeans, but little to distinguish the Senegalese from the Solomon
Islanders. The same is true for any other feature of our bodies. The
shapes of our eyes, noses and skulls; the color of our eyes and our
hair; the heaviness, height and hairiness of our bodies are all,
individually, poor guides to ancestry. But this is not true when the
features are taken together. Certain skin colors tend to go with
certain kinds of eyes, noses, skulls and bodies. When we glance at a
stranger's face we use those associations to infer what continent, or
even what country, he or his ancestors came from - and we usually get
it right. To put it more abstractly, human physical variation is
correlated; and correlations contain information. Genetic variants that
aren't written on our faces, but that can be detected only in the
genome, show similar correlations. It is these correlations that Dr.
Lewontin seems to have ignored. In essence, he looked at one gene at a
time and failed to see races. But if many - a few hundred - variable
genes are considered simultaneously, then it is very easy to do so.
Indeed, a 2002 study by scientists at the University of Southern
California and Stanford showed that if a sample of people from around
the world are sorted by computer into five groups on the basis of
genetic similarity, the groups that emerge are native to Europe, East
Asia, Africa, America and Australasia - more or less the major races of
traditional anthropology."

New research shows that 'Human races are evolving away from each other.Genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin. We are getting less alike, not merging into a single, mixed humanity. This is happening because humans dispersed from Africa to other regions 40,000 years ago, and there has not been much flow of genes between the regions since then'(Harpending)


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