Re: Good mutations

Glenn Morton (
Fri, 28 Nov 1997 20:54:14 -0600

Hi John,

At 09:54 PM 11/27/97 -0600, John P. McKiness wrote:

>Just a quick note on you statements above. I believe we white folk are the
>ones who need to be thankful for the mutations that lead to our light skin
>because dark skin, in all likely hood, is the original condition in our
>species. Higher melanin content is the norm in the tropics and subtropics.
>Light skin pigmentation is the result of beneficial mutations within mid to
>high latitude populations. The need for vitamin D and lower light
>intensity requires less pigment (unless we can get vitamin D somewhere
>else). Less pigment on the other hand would be a harmful mutation in the
>tropical savanna of Africa.

I have seen some controversy about this. Apparently, even with only 3 hours
of sunlight per day even at high latitudes, blacks can produce their maximum
quota of vitamin D. (John H. Relethford, Fundamentals of Biological
Anthropology, (Toronto: Mayfield Publishing Co., 1994), p. 112) The
occurrence of rickets among blacks increased when they moved to the cities
and were no longer spending those 3 hours outside in the sun. There is
another possible selective need for light skin at high latitudes:

"Recently, there has been some evidence that skin colors are linked to
differences in the ability to avoid injury from the cold. Army researchers
found that during the Korean War blacks were more susceptible to frostbite
than were whites. Even among Norwegian soldiers in World War II, brunettes
had a slightly higher incidence of frostbite than did blonds."~Boyce
Rensberger, "Racial Odyssey," in Elvio Angeloni, Editor, Annual Editions
Physical Anthropology 94/95,(Sluicedock,Guilford, Conn.: The Dushkin
Publishing Group, Inc., 1994), p.40-45, p. 42

Blue eyes are also more sensitive to red light and dimmer illuminations than
brown eyes. Ibid. p. 42-43


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