Salsassin Wrote:
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> I don't think the amount of melanin production in
> the skin or hair is a huge mutation.
I don't know why we are spending so much time and effort dealing with a "scientific creationist" troll. Skin color is due to a combination of several genes (4-8) because of this skin color appears as a huge range not an on-off switch as would be indicated for a one gene Mendek=lian trait (there is no either "black" or "white") Thus all this blather about a "mutation" is irrelevant. Further, skin color is adaptive so that what we find is a cline correlated with UV intensity and thus is irrelevant to determining geneticrelatedness (i.e. "race")-- or genetic relatedness between Egyptians and West African sub-Saharan Africans. Here is a recent paper on the topic:

N.G. Jablonski and G. Chaplin. 2000. “The Evolution of Human Skin coloration” Journal of Human Evolution 39: 57-106.

Skin color is one of the most conspicuous ways in which humans vary and has been widely used to define human races. Here we present new evidence indicating that variations in skin color are adaptive, and are related to the regulation of ultraviolet (UV) radiation penetration in the integument and its direct and indirect effects on fitness. Using remotely sensed data on UV radiation levels, hypotheses concerning the distribution of the skin colors of indigenous peoples relative to UV levels were tested quantitatively in this study for the first time.
The major results of this study are: (1) skin reflectance is strongly correlated with absolute latitude and UV radiation levels. The highest correlation between skin reflectance and UV levels was observed at 545 nm, near the absorption maximum for oxyhemoglobin, suggesting that the main role of melanin pigmentation in humans is regulation of the effects of UV radiation on the contents of cutaneous blood vessels located on the dermis. (2) Predicted skin reflectances deviated little from observed values. (3) In all populations for which skin reflectance data were available for males and females, females were found to be lighter skinned than males. (4) The clinal gradation of skin coloration observed among indigenous peoples is correlated with the UV radiation levels and represents a compromise solution to the conflicting physiological requirements of photoprotection and vitamin D synthesis.
The earliest members of the hominid lineage probably had a mostly unpigmented or lightly pigmented integument covered with dark black hair, similar to that of the modern chimpanzee. The evolution of a naked, darkly pigmented integument occurred early in the evolution of the genus Homo. A dark epidermis protected sweat glands from UV-induced injury, thus assuring the integrity of somatic thermoregulation. Of greater significance to individual reproductive success was that highly melanized skin protected against UV-induced photolysis of folate (....), a metabolite essential for normal development of the embryonic neural tube (...) and spermatogenesis (...).
As hominids migrated outside of the tropics, varying degrees of depigmentation evolved in order to permit UVB-induced synthesis of previtamin D3. The lighter color of female skin may be required to permit synthesis of the relatively higher amounts if vitamin D3 necessary during pregnancy and lactation.
Skin coloration in humans is adaptive and labile. Skin pigmentation levels have changed more than once in human evolution. Because of this, skin coloration is of no value in determining phylogenetic relationships among modern human groups.

[Anon.2000. “Selective Power of UV” Science 289: 1461. Group at California Academy of Science has done the first study that confirms this connection [skin color and sunlight exposure] with direct measures of solar radiation. Anthropologists Nina Jablonski and George Chaplin at CAS in San Francisco used data from NASA satellites collected from 1978 t0 1993 to compute average annual exposure to ultraviolet (UV) radiation in different areas of the world. They compared the sunlight map with data on skin reflectance- the higher the reflectance, the lighter the skin-- from ethnic groups in more than 50 countries. Increasingly light skin matches up with decreasing UV levels, the authors report.... One exception to the pattern says Jablonski, is indigenous American populations, which are lighter colored than would be predicted from UV levels. That, she says, is “probably because of the relative recency of their migration” and because they had more clothing and shelter than their ancestors.]


Bernard