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Origin Of Light Skin In Africa
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[QUOTE]Originally posted by Elmaestro: [QB] Here's an easy way to digest this, as someone who literally had to write a book on the melanogenic pathway through the lens of genetics, evolutionary and molecular biology. How this works is quite simple, early humans (possibly after becoming hairless) acquired integument pigmentation to no discrimination. The pathway to create adequate melanin (specifically eumelanin) is very frugal, convoluted and capricious. By that nature alone would we expect early Anatomically modern humans with no long term selection pressure to spontaneously develop a variety of shades... It wasn't the Khoisan who forcefully became lightened, it was Africans under harsh selective pressures who became darkened, and not only by UV intensity. Melanin had minor antitoxic, antibiotic and regenerative properties, very much needed in heavily forested, humid and/or moist areas for example. If you wan't to know what early humans probably looked like... Look at the variation among African Americans and pay attention to tanning. Tanning is an adaptive process, referred to as 'Active Melanogenesis' where the intensity or temporal exposure of UV radiation significantly boosts the process of synthesizing melanin polimers and distributing them into the skin and hair via phagocytosis (presumably). Humans have an inherit mechanism to Darken their skin drastically. [b]We didn't start pitch black and gradually lightened[/b] The two popular mutations slc24a5 and slc45a2 primarily disrupt protein transport after the polimer is synthesized, this is why I refer to the melanogenic pathway as capricious, or even fickle. There are many many mutations in different genes that can result in the same thing, it's just that these two where "selected for" in Europeans and is responsible for around 40% of the differences between light and dark populations TODAY. There are many forms of Albinism, though I do like to point out the hypocrisy in "diagnosing" Albanism in primarily dark skinned populations, I don't feel it's appropriate or necessary to refer to our not-so-melanated brothers and sisters as Albinos. But yes mutations in the same genes for the most part that'll be labeled as albinism result in skin eye and hair color variation across the globe. In regards to mixing, Europeans didn't invent light skin, but novel mutations are loyal to no one people or continent. Meaning, if a particular mutation arose primarily in Europeans and that same mutation later on is found in a mixed descendant, than thats how the cookie crumbles, you have an offspring with a European gene for pigmentation and that's it. [/QB][/QUOTE]
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