BoatBanter.com - My ass burns

In article ,
Phoon Hencman wrote:

On 2007-09-14 11:59:53 -0400, "Doug Kanter"
said:

and itches. Know of a cure?

Yes, a gunshot to the head.

Take ad libitum.

August 27, 2000 Sunday Press Democrate (N.Y. Times) B5

UV light, skin color linked

Variations due to geography

Associated Press

SAN FRANCISCO - Two San Francisco scientists using data from a NASA
satellite say they have discovered why people come in different colors.

Variations in human skin color are the result of adaptations to the
amount of ultraviolet light from the sun falling on different regions of
Earth, according to Nina Jablonski and George Chaplin, scientists with
the California Academy of Science.

People's bodies change their skin color over time to let in just the
right amount of UV light, which is key to having healthy babies.

UV light affects the skin's production of folate, part of the B vitamin
complex, and vitamin D-3, both of which are essential for having healthy
children.

Folate is necessary for the proper development of the nervous system in
fetuses and for sperm production in adult males. Vitamin D-3 helps build
and maintain strong bones and a healthy immune system.

But too much solar UV light can not only cause skin cancer, it can also
damage those chemicals, thereby hurting a person's chances for
reproductive success.

The scientists' finding may also explain why women tend to be
lighter-skinned than men. Lighter skin lets in more solar UV light,
increasing a woman's vitamin D-3 production, which helps the fetus grow
during pregnancy and helps nourish newborns through breast feeding.

UV light from the sun varies from region to region for reasons including
latitude, humidity and cloudiness.
Jablonski and Chaplin's discovery isn't entirely new. For a long time,
scientists have thought there was a correlation between UV light and
skin color, and they knew the light helped produce vitamin D and that it
could cause cancer.

"But this explanation was considered weak by some scientists because
skin cancer has little or no effect on people's ability to reproduce,
which is really the bottom line of every evolutionary spreadsheet,"
Jablonski said.

Jablonski developed the hypothesis that links UV light to reproduction
in 1991. The scientists analyzed published measurements of human skin
color from around the world and data from NASA's Total Ozone Mapping
Spectrometer satellite, which orbited Earth from 1978 to 1993 and
gathered direct UV measurements for the entire globe to find the
correlation between skin color and UV light.

Jablonski and Chaplin found that dark skin acts as a natural sunscreen
to help prevent UV light from breaking down folate, so it is helpful in
areas with a lot of sun. But in less sunny areas, dark skin screens out
too much sunlight, and can inhibit the production of vitamin D-3, so
lighter skin is helpful for reproductive success.

Skin color is based on the level of melanin, an organic molecule with an
undetermined chemical structure. Those with more melanin have darker
skin, and melanin levels are genetic. But the variations in skin color
are adaptations to solar UV light, not biological differences among
people, according to Jablonski and Chaplin.
"We're all the same under the skin," Jablonski said.

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Billy

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