Jablonski on evolution of skin color

[anthrostudies]

I have to say something about the first abstract.
CLICK HERE FOR ABSTRACTS IN ORIGINAL TOPIC
The purest African pygmies have a reddish skin, and Capoids (including East African Capoids) have a yellowish coloured skin. As a result, since these populations were the first human groups to seperate (based on genetic evidence), bracketing suggests that dark skin is probably not present in the first moderns.

[Daryl Habel]

I have to say something about the first abstract.

The purest African pygmies have a reddish skin, and Capoids (including East African Capoids) have a yellowish coloured skin. As a result, since these populations were the first human groups to seperate (based on genetic evidence), bracketing suggests that dark skin is probably not present in the first moderns.

Hi anthrostudies,

Sorry about moving things around, but I did want to reply to your comment, and since Jacques would prefer comment to be placed in a proper context, I've moved your comment above to this board and given it a new title.

I disagree with your conclusion.  You reason the "pygmy/capoid" split were the first human groups to separate (according to genetics)  and since their skin is "reddish" and "yellowish" that suggests dark skin is probably not present in the first moderns.   I would say that it would seem impossible to use this as reasoning on the grounds that, as Jablonski says in the abstract (below), "melanin pigmentation... has been maintained by natural selection" and is evolutionarily labile, therefore "skin color phenotype is useless as a unique marker of genetic identity."

If it is true that "pygmy/capoid" represents the split of the oldest modern humans, following the genetics, then that split was probably about 100,000 years ago.   Plenty of time for lots of evolutionary adaptation in skin color.  Earliest  African "moderns" probably were dark-skinned, but the degree of melanin adaptation would depend on their geographic context (wherever that was), rather than the skin coloration of descendants with 100k years of adaptation.

Dar

That said, I'll now repost the Jablonski abstract:
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Jablonski, Nina G. 2004. The Evolution of Human Skin and Skin Color. Annual Review of Anthropology (see below for publication date).

Abstract:
Humans skin is the most visible aspect of the human phenotype. It is distinguished mainly by its naked appearance, greatly enhanced abilities to dissipate body heat through sweating, and the great range of genetically determined skin colors present within a single species. Many aspects of the evolution of human skin and skin color can be reconstructed using comparative anatomy, physiology, and genomics. Enhancement of thermal sweating was a key innovation in human evolution that allowed maintenance of homeostasis (including constant brain temperature) during sustained physical activity in hot environments. Dark skin evolved pari passu with the loss of body hair and was the original state for the genus Homo. Melanin pigmentation is adaptive and has been maintained by natural selection. Because of its evolutionary lability, skin color phenotype is useless as a unique marker of genetic identity. In recent prehistory, humans became adept at protecting themselves from the environment through clothing and shelter, thus reducing the scope for the action of natural selection on human skin.

[anthrostudies]

Hi anthrostudies,

Sorry about moving things around, but I did want to reply to your comment, and since Jacques would prefer comment to be placed in a proper context, I've moved your comment above to this board and given it a new title.

It's ok, its for the best that it should have been moved.

I disagree with your conclusion.  You reason the "pygmy/capoid" split were the first human groups to separate (according to genetics)  and since their skin is "reddish" and "yellowish" that suggests dark skin is probably not present in the first moderns.   I would say that it would seem impossible to use this as reasoning on the grounds that, as Jablonski says in the abstract (below), "melanin pigmentation... has been maintained by natural selection" and is evolutionarily labile, therefore "skin color phenotype is useless as a unique marker of genetic identity."

I haven't read the paper, so I can't argue against it. I wasn't saying that it is impossible, but when I was inferring wether dark skin was present in the common ancestor, from bracketing, I was using a standard practice. So I have to caution that not all evidence supports dark skin in the common ancestor.

[Daryl Habel]

Beyond the abstract, I haven't read it either, so I could very well be confused about what it specifically says.  But IIRC this is not the first paper that Jablonski has published on this subject.  I'll have to dig for the other reference I've seen.  Much logic depends on the eventual outcome of the OoA/MRE debate, but it seems to me that using genetic data as the foundation for reasoning,  the ancestral African population probably was dark skinned (IF sub-Saharan), unless  these people who "replaced" all other populations were actually from the North African Mediterranean region or some other temperate area well north of the equator.  Problem is I don't think anyone has ever proven where the Africans lived  that spawned the OoA "replacement" (if you believe that) of all other archaic populations.

As always, its best to read first and comment later.  I'll have to see about acquiring the Jablonski paper.

Dar

 

[goswinus]

Furless animals in equatorial regions usually are large-bodied and their skin turned dark grey or brown; the hippopotamus has a red pigment that protects the skin against the sun like tanning oil, which might even heal wounds from infection.

The bare skin in domestic and smaller kind of animals is spotted with patches of greyish tones and random white, white-rosey body parts, so far I know they don't posses a physiological back-up system to protect their exposed skin and one might conclude that when the hominids shed their fur, they risked to jeopardize their future, stranding them in an evolutionary cul-de-sac, unless they knew to find a solution to their predicament before their bodies underwent slow-moving adaptations and while the process took place, some light-skinned(freckled?) groups might have moved out from the savannah to seek out more temperate life zones. Meanwhile who remained behind struggled generation after generation against the blazing sun and acquired a reddish or yellow brown skin, though considering the case of the Central African Pygmees, what adaptive advantage entails a dark skin in a canopious mileu?