Possible benefit for long head hair on humans?

I was under the impression that things evolved for a reason - that they are of some benefit… or else they’re things that used to be of some benefit (vestigial organs/body parts).

But what about long hair? Why do all humans have it? If it is so useful, why do some hunter gatherers (e.g. many African ones) shave it all off? If it was allowed to just grow I thought an “Afro” and a long beard would be a problem. Maybe it could allow bacteria to breed or something.

Next, why do men have other head hair - beards? And hair on the back of their neck. As far as I know normally only mature males grow hair on the back of their necks.

Then there is pubic hair… and hair under the arm pits and leg hair… does that have or has had any survival benefit?

I wonder when long hair was meant to have evolved. Normally our ancestors are portrayed as being ape-like with no long hair. BTW apes are in hot climates and cold climates and they don’t need long head hair…

Edit: the title isn’t quite accurate - I’m also asking about non-head hair.

Temperature control. For heads, it strikes me that African hair would be good for evaporative cooling.

That is a good question, but I don’t really know the benefits. We assume maybe too much that everything has an evolutionary benefit, sometime perhaps they don’t. What is the purpose of public hair, or under arm hair? So many questions.

I don’t know if long hair today has a purpose. In primitive times it was dangerous because it made hunting more difficult and in a fight your enemy can pull your long hair.

I just don’t know.

I don’t have hair on my neck, though I have hair most elsewhere except the back. Regarding body hair I know we lost it because now we have no use for it, we wear clothes, but early humans needed body. But it still remains to extent.

As far as hunter-gathering Africans go it is common for the men to shave off all of their hair. And some have it long and platted. For athletes they’d normally keep it short… I don’t think an athlete with uncut hair (and beard) would have an advantage.

BTW I was thinking about horses - they often have long hair on their heads too.

I was talking about pubic hair and underarm hair. I lived in a desert for 11 years. Loose shorts and shirts allow circulation around the sweaty hairy bits, cooling the areas by evaporation.

ISTR hearing since that time that sperm is temperature sensitive, and pubic hair regulates the temperature there; but I don’t have a cite for that and I don’t recall hearing about reproductive functions for females.

Sorry I didn’t look at the text you quoted. BTW if underarm hair and pubic hair is so good then I thought people would just be hair all over. Also I thought children would have it too… maybe it is sort of a visual indicator as to whether someone is mature.

“endurance running is only seen in humans” - this is about sweating and less hair that is on humans that allow them to keep running until their prey has to pant and slow down.

BTW about pubic hair again, you said “sperm is temperature sensitive” so I guess it is unnecessary in children.

Actually you did also say “For heads, it strikes me that African hair would be good for evaporative cooling.”

“Although many mammals sweat, few have evolved to use sweating for effective thermoregulation, humans and horses being notable exceptions.”

Horses are mentioned again - I mentioned them earlier when talking about the hair they have on their heads.

Nope, things that don’t prevent life until reproduction age will be happily passed on benefit or not!

CMC fnord!

The Master has spoken:

As crowmanyclouds indicates, traits do not evolve in order to suit a particular purpose. That would actually be how Intelligent Design or straight-up Creationism would work.

Evolution more or less evolves to eliminate traits that hinder reproduction. If it doesn’t keep you from passing on your genes, there is no particular reason for it to go away, even if it does absolutely nothing for you. You may evolve new traits due to mutation, but they may either be of benefit (yay!), detriment (in which case that branch might die off because folks with that trait didn’t reproduce) or Zero-sum (it has no effect on your ability to reproduce, and will probably continue to be evident as long as the branch containing that trait doesn’t get killed off for some other reason).

EDIT: Note, this specifically applies to benefits or detriments to reproduction. If someone evolved a trait that lead to abrupt death in their mid-30s, while that is a definite drawback, it doesn’t necessarily prevent reproduction, and thus might get passed on for many generations. Of course, if folks with said trait don’t want to conceive children that will inherit such a trait, then it does in fact prevent reproduction (for social, rather than biological reasons)

But why do basically ALL humans have long head hair (and beards for mature males)? It thought it being beneficial in some way would be the reason.

Like I was saying earlier, I think the reason horses have long head hair may be similar to the reason why humans have long head hair… and horses don’t tie ribbons in their hair. Though people do (e.g. playing with toy horses/ponies)

About sexual selection - people still mate with bald men and sometimes even bald women… for head hair to be universal baldness should be quite repulsive.

And for some folks it is. And then again, for other folks, it serves to distinguish them from their peers (probably helps if the bald person is awesome for non-hair-related reasons, such as Sir Patrick Stewart).

You’re right, horses and humans do have long head hair for the same reason: It doesn’t prevent them from getting laid. Remember: Evolution selects against negative traits, not for positive ones.