Genes, Skin Color, Sex, and Europe Only?

Gene That Determines Skin Color Is Discovered, Scientists Report

By NICHOLAS WADE
Published: December 16, 2005
New York Times

A gene that is responsible for the pale skin of Europeans and the dark skin
of Africans has been discovered by scientists at Pennsylvania State
University.

The gene comes in two versions, one of which is found in 99 percent of
Europeans and the other in 93 to 100 percent of Africans, the researchers
report in today's issue of Science.

The gene is unusual because with most human genes, different versions are
generally shared, though one version may be more common in one race than
another. One exception is the Duffy null allele, a version of a gene that
prevents malaria, that is found almost exclusively in one race, sub-Saharan
Africans.

The new gene falls into the same category as the Duffy gene, and it may shed
light on the evolutionary pressures to which Europeans were subjected as
their ancestors, who were presumably dark skinned, moved into the northern
latitudes some 40,000 years ago.

Humans acquired dark skins in Africa about 1.5 million years ago to shield
their newly hairless bodies from the sun. Its ultra-violet rays destroy
folic acid, a shortage of which leads to birth defects.

But when the modern humans who left Africa began to live in northern
latitudes, they needed more sunlight to penetrate the skin, to permit the
chemical reaction that produces vitamin D.

The new gene was first identified not in humans but in a mutant zebra fish,
a small striped fish common in aquariums. The mutant fish are known as
golden, because their stripes, usually black, are much paler and their
bodies more yellow.

Dr. Keith C. Cheng, an author of the report, and his colleagues showed that
the golden version of the fish gene altered production of melanosomes, the
tiny black particles of pigments that give skin its color.

The researchers then found that in humans, who have their own form of the
gene, the version common in Africans allowed larger melanosomes, which tend
to clump together, whereas the version in Europeans produced smaller and
more dispersed melanosomes.

Asians have the same version of the gene as Africans, so they presumably
acquired their light skin through the action of some other gene that affects
skin color, said Dr. Cheng.

Mark D. Shriver, another author of the article, said his laboratory was
trying to assess when the European version of the gene became so common, as
well its geographical origin.

The intense selective pressure that drove the version to become universal in
Europeans may have included sexual selection.

"In Africa people are much darker than they need to be for UV protection, so
to me that screams sexual selection," Dr. Shriver said. Black skin, in other
words, may have been favored by men and women in sexual partners, just as
pale skin may have been preferred in sexual partners among Europeans and
Asians.

------------------------------------------

Holy Cow! Wouldn't it be just as easy to say that "Europe Only" light
skinned genes came from the Neanderthals?

That African skin color is darker than it needs to be sounds pretty wierd.
It isn't as if all Africans have the same depth of color.

No article sited? Not published yet?

Jois


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