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Evolution of "Afro hair"

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I would assume that afro hair developed as a way of protecting against UV radiation. My question is, why didn't any other mammals develop a similar style of hair? It seems odd that only humans developed this trait.

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According to Molnar's "Human Variation";

 

"The adaptive signifiance of hair form is not understood, but it is likely that certain forms, woolly or spiral, allow for an air space between the scalp and the outer edges that insulates the head from the intensity of the sun's heat in the tropics"

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The assumption is probably invalid. After all, humans have so little hair that having it kinky is not going to provide enough protection from UV. UV breaks down folate (a B vitamin) and the result of too little folate is neural tube defects during embryogenesis -- babies are born with seriously impaired CNS.

 

We don't know the adaptive advantage (if there is one) of kinky hair. Since humans went thru a severe bottleneck in population about 150,000 years ago, this may simply be a result of genetic drift and a feature getting fixed by accident in a small population.

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I read somewhere that some racial features. ex - hair thickness, nose width, eye shape... were probably sexually selected traits.

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Im not very sure of the properties of "Afro hair", but me thinks it may be selective via a way of trapping moisture like a sponge to aid in cooling.

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Could it be because animals don't need it?

 

The hair could be a fluke or it could be a barrier to UV radiation, protecting the head, which makes sense since it's the most exposed to the sun and contains the brain.

I read the Wikipedia article it's pretty good.

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I would assume that afro hair developed as a way of protecting against UV radiation. My question is, why didn't any other mammals develop a similar style of hair? It seems odd that only humans developed this trait.

 

Umm...how exactly is wool not a similar trait? (FYI, I was unable to open the link you provided, so if there is an explaination there, I would appreciate if you could summarize here).

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Im not very sure of the properties of "Afro hair", but me thinks it may be selective via a way of trapping moisture like a sponge to aid in cooling.

 

Wow I feel like a retard and smart at the same time... I clicked the link and it was the first discription of selective possibilitys..... damn... retard

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Just out of curiosity...................what would the advantage of having thin strait hair be?

 

Since i was so keen the first time.. Ill guess. Afro hair cant grow down the shoulders.. it may help in heat retention... I would guess it has to do alot with sexual selection though.. Cuacasions people dont tend to be attracted to afro hair that much... and maybe a Afrikaner can chime in, but they probably still love strait hair.

 

Perhaps this can be seen sociologically with the 1920's ish style where black people would straigten there hair? aka sugar ray robinson (and many more, those that watch tv/movies should get this)

Edited by blazarwolf
I concluded Cauc's and Afrikaner are the most logical discriptors

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On 9/18/2008 at 4:23 AM, blazarwolf said:

Im not very sure of the properties of "Afro hair", but me thinks it may be selective via a way of trapping moisture like a sponge to aid in cooling.

If that were the case, then wouldn't other primates have had this same/similar hair texture? Not convinced, not convinced at all...

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On 10/8/2019 at 9:45 PM, EastNamibianSpaceMiningCo said:

If that were the case, then wouldn't other primates have had this same/similar hair texture? Not convinced, not convinced at all...

We do. The hair around my groin is much more Afro than the hair on my head. It's also thicker. So much so, that we humans have evolved two different types of lice. Head lice, or nits, adapted to head hair, and pubic lice, or crabs, for the groin. Pubic lice need hair of a greater diameter to cling to, so you find them mainly on the pubes, but sometimes on the eyebrows and (I think) armpits. But they can't live on head hair, it's too thin. And it's pretty much vice-versa for the nits. 

DNA studies indicate that the nits colonised humans first, and that the crabs are descended later from Gorilla lice, which found a home on the thicker hair around human pubes. 

Like you, I'm not convinced by the sponge idea above. Trapping moisture would inhibit cooling, by preventing evaporation. Instead of cooling, the sweat is more likely to run off as a liquid. Bare skin would lose the most heat from the body. Moisture that evaporates off a hair takes more heat from the ambient air rather than the blood, whereas moisture evaporating off bare skin cools the blood. 

There are lots of ideas why hair grows this way or that, but nobody knows for sure. I think it's probably down to sexual selection. There is a tendency to select what you grew up with as being most attractive. But there's another tendency to be attracted to the "exotic". And having said that, sex is so strong an instinct that easily overrides such tendencies and can make them pretty irrelevant. 

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Quote

Clarence (2012) suggests that afro-textured hair may have initially evolved because of an adaptive need amongst humans' early hominid ancestors for protection against the intense UV radiation of the sun in Africa.[11] With regard to the hypothesized recent African origin of modern humans, the author argues that afro-textured hair was the original hair texture of all modern humans prior to the "Out-of-Africa" migration that populated the rest of the globe.[11]

According to Clarence (2012), afro-textured hair may have been adaptive for the earliest modern humans in Africa because the relatively sparse density of such hair, combined with its elastic helix shape, results in an airy effect. The resulting increased circulation of cool air onto the scalp may have thus served to facilitate the body-temperature-regulation system of hominids while they lived on the open savannah.[11] Afro-hair requires more moisture than straight hair and tends to shrink when dry. Instead of sticking to the neck and scalp when damp (as do straighter textures), unless completely drenched it tends to retain its basic springiness. The trait may have been retained and/or preferred among many anatomically modern populations in equatorial areas, such as Polynesians, Micronesians, Melanesians, Australoids and the Negrito, because of its contribution to enhanced comfort levels under tropical climate conditions.[11]

https://en.wikipedia.org/wiki/Afro-textured_hair

 

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