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Author Topic:   Skin colors and latitude
Randy
Member (Idle past 5086 days)
Posts: 420
From: Cincinnati OH USA
Joined: 07-19-2002


Message 38 of 65 (160792)
11-17-2004 10:43 PM
Reply to: Message 37 by Parsimonious_Razor
11-17-2004 9:18 PM


quote:
One of the effects of strong estroginization is a lightening of the skin and hair. Men prefer lighter skin and hair tones with in the normal range of their culture. So men living in environments with darker skinned people will have a preference for a darker skinned women then in say, Norway, but the preference will be for the lighter skin with in his subset. This is the only evidence that I know of in regards to sexual selection for skin tones.

So that's why the girls I knew when I was a teenager spent so much time working on their tans and why women go to tanning booths and buy sunless tanning products. Or is it the other way around?

There is a preference for lighter skin tones in Asia and skin lightening products are big there but IMO these differences are primarily cultural.

IMO the aforementioned paper by Jablonski and Chaplin makes a good case for the protection argument basing it more on protection of sweat glands and prevention of folic acid breakdown than on protection from sunburn. I have just obtained the paper on antimicrobial affects of melanin and haven't had time to read it yet.

I am not sure if it has been discussed on this thread but I think that I have previously posted that skin color variations are primarily controlled by the interaction of two hormones Apha melanocyte stimulating hormone and agouti signalling protein with the Melanocortin 1 (MC1R) receptor. This interaction controls the amount of the dark eumelanin containing pigment granules (eumelanosomes) and reddish pheomelanin containing pigment granules (pheomelanosomes) that are produced and transferred from the melanocytes to the keratinocytes. MC1R is highly polymorphic in humans with at least 65 known alleles with nonsynonomous changes at last count (Reese, Am J Hum Genet. 2004 Nov;75(5):739-51 ) and many of the varients are associated with differences in skin and hair color and sun sensitivity. A less well known factor in skin color is the tendancy of the melanosomes in dark skin to be indvidually distributed and bound in clusters in lighter skin. Our work indicates that this is controlled by the keratinocyts and not the melanocytes (Minwalla et al. J Invest Dermatol. 2001 Aug;117(2):341-7) so MC1R polymorphism is probably not the only genetic variable affecting skin color even though it is a major one.

Randy
PS Anyone interested in how sunless tanners work can see my little FAQ answer in the August issue of Scientific American. (or you can read it online http://www.sciam.com/askexpert_question.cfm?articleID=0009B2C1-E30D-106D-9D7E83414B7F0000

This message has been edited by Randy, 11-17-2004 11:00 PM


This message is a reply to:
 Message 37 by Parsimonious_Razor, posted 11-17-2004 9:18 PM Parsimonious_Razor has responded

Replies to this message:
 Message 42 by MangyTiger, posted 11-18-2004 3:56 PM Randy has not yet responded
 Message 43 by Parsimonious_Razor, posted 11-18-2004 4:25 PM Randy has not yet responded

  
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