According to what I remember from some random wikisurfing way back when, it was sort of a backwards-mutation. Basically, we all started out white (most animals are), but lost our fur, meaning we were exposed to nasty, nasty, kill-us-with-cancer UV, which was kind of bad. First humans developed Black hair, to protect our heads, since we stood upright and our heads were the most exposed to direct sunlight, and as a way to block some of the sun's rays (light doesn't travel well through spirals, after all). After that, humans developed black skin. Then we started migrating, and humans moved to places with less sun, where black skin was a detriment because women weren't getting enough vitamins from sunlight (I think vitamin D or A, but I'm blanking and too lazy to look up; it's a vitamin we synthesize from sunlight and women need for healthy pregnancies). So their skin lightened and their hair straightened, because straight hair carried sunlight better, kind of like an fiber optic tube. And darker-skinned people from other parts of the world have straight hair because they redevelopped dark skin after they developed straight hair, and having darker skin meant they didn't need Black hair to protect their heads, so there was no real reason to revert back to it, so their hair stayed straight.
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 insuring the integrity of somatic thermoregulation. Of greater significance to individual reproductive success was that highly melanized skin protected against UV-induced photolysis of folate (Branda & Eaton, 1978, Science201, 625-626; Jablonski, 1992, Proc. Australas. Soc. Hum. Biol.5, 455-462, 1999, Med. Hypotheses52, 581-582), a metabolite essential for normal development of the embryonic neural tube (Bower & Stanley, 1989, The Medical Journal of Australia150, 613-619; Medical Research Council Vitamin Research Group, 1991, The Lancet338, 31-37) and spermatogenesis (Cosentino et al., 1990, Proc. Natn. Acad. Sci. U.S.A.87, 1431-1435; Mathur et al., 1977, Fertility Sterility28, 1356-1360).
When they refer to early hominids with 'light pigmentation', they're not referring to the homo linage but their preceders, who are not human by any definition. They conclude that the genus homo was darkly pigmented... and the genus homo (starting with homo habilis) is about 3 billion years old, presuming by they time we arrived in the modern human era (1 billion-500 million years ago onward) and the Out-of-Africa migration waves, people were quite pigmented.
"the genus homo (starting with homo habilis) is about 3 billion years old, presuming by they time we arrived in the modern human era (1 billion-500 million years ago onward) and the Out-of-Africa migration waves, people were quite pigmented."
Cool, thanks. I was pretty much going off memories I read of stuff off wiki from, oh, well over a year ago, so while I remember the order of it all, my memory of when in the timeline all this stuff exactly happened is muddy.
Oddly, my daughter and I were talking about this yesterday in reference to her complaint that she burns so easily in summer.
It's ironic that the one marker - skin color - that is most used by racists to distinguish human populations is actually an adaptation that occurs over a relatively short period and has few implications that can't be compensated for by sunscreen and vitamin pills.
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Yeah, my mom has straight, black hair and can be a real hot-head, here in the desert. My curly browns keep me a lot cooler.
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The evolution of human skin coloration (Journal of Human Evolution, 2000)
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 insuring the integrity of somatic thermoregulation. Of greater significance to individual reproductive success was that highly melanized skin protected against UV-induced photolysis of folate (Branda & Eaton, 1978, Science201, 625-626; Jablonski, 1992, Proc. Australas. Soc. Hum. Biol.5, 455-462, 1999, Med. Hypotheses52, 581-582), a metabolite essential for normal development of the embryonic neural tube (Bower & Stanley, 1989, The Medical Journal of Australia150, 613-619; Medical Research Council Vitamin Research Group, 1991, The Lancet338, 31-37) and spermatogenesis (Cosentino et al., 1990, Proc. Natn. Acad. Sci. U.S.A.87, 1431-1435; Mathur et al., 1977, Fertility Sterility28, 1356-1360).
When they refer to early hominids with 'light pigmentation', they're not referring to the homo linage but their preceders, who are not human by any definition. They conclude that the genus homo was darkly pigmented... and the genus homo (starting with homo habilis) is about 3 billion years old, presuming by they time we arrived in the modern human era (1 billion-500 million years ago onward) and the Out-of-Africa migration waves, people were quite pigmented.
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not billion, million
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Ahmadinejad affairs have eaten my brain.
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It's ironic that the one marker - skin color - that is most used by racists to distinguish human populations is actually an adaptation that occurs over a relatively short period and has few implications that can't be compensated for by sunscreen and vitamin pills.
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