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Question about hair and evolution

Okay, I hope this is the right group to ask this in; I've been haranguing my wife about this, and she teaches high school English -- it's not in her wheelhouse.

So if you look at any other primate beyond humans, their hair doesn't grow all that long -- at least not in comparison to humans. Orangutans seem to get the shaggiest, maybe a foot-long at best.

But orangutans don't compare to most of the women in my apartment complex with hair down to their mid-back. I've had two-foot long hair, and my wife has had hair nearly to her butt. I saw a guy from India the other day who had the world's longest beard.

Question: Of what use is having hair that grows indefinitely like that? Was there a time in human evolutionary development where it didn't grow as long, and after we figured out how to sharpen a flint and shave ourselves it started to grow longer? Or does the hair of other primates just break off before it turns into Rapunzel?

Because I get the warmth/protection factor, but it seems like having hair that could trip you while running from danger or after game seems more of a selective disadvantage than advantage. Our woollier ape brethren whose hair only seems to grow to a certain length seem to have a step up on us here.

Or is there some use for five feet of hair hanging down to your knees that I clearly don't get?

I understand that cutting hair will make it grow faster, but that doesn't mean as soon as people started cutting their hair that it started to grow longer -- just look at people who never cut their hair. Did we all just run around in dreads at some point?

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Replies to This Discussion

Permalink Reply by ɟǝןıx dǝʇɹɐɹ on May 16, 2010 at 10:01am

cutting hair will make it grow faster

That's just a myth. There are no receptors in the hair that signal to the hair roots that the hair is cut.

If you don't believe this, I would add that my final paper when I graduate medicine was about the permanent hair loss pathologies. :)

Permalink Reply by mxyzptlk on May 17, 2010 at 1:37pm

Heh -- that's just what my wife tells me. Maybe it just seems like that after losing split ends. Mine's cropped anyway.

But I'm still not sure why we grow hair like vines, and other primates seem to have the sense to have hair that doesn't get in their way.

Permalink Reply by ɟǝןıx dǝʇɹɐɹ on May 20, 2010 at 10:49pm

I guess that women that have very long hair took care of it and cut the split ends. I'm trying to remember any primitive society that has members with very long hair that they step on it. The Africans could have very long hair and still be all compacted on the head.

Maybe if people don't take care of their hair, the hair doesn't have a chance to grow very long and breaks sooner.

Another thing is that you may be right and we evolved with cutting hair like with the fire and other tools. You may be on something...

Permalink Reply by Jared Lardo on August 7, 2010 at 5:31pm

All I can figure is that it, having come about as the result of mutations, was attractive, so that those with the ability to display their health and nutrition as hair allows, were sexually selected-for.

I'm no geneticist; so, I haven't got a clue about the details of the mutations ("Over here, here, and over there in the genome, about so many oodles of years ago."), but overall, since attractive hair is healthy hair which tends to be on a healthy person, that's why we've got that hair thing going on.

Permalink Reply by Taran Meyer on October 19, 2010 at 1:28pm

Very belatedly, I'd agree that this probably evolved as a result of sexual selection and display. Long, ever-growing hair requires looking after of some kind, whether cutting, grooming, plastering with mud, or twisting into dreadlocks, and every single human culture on the planet does SOMETHING with their hair. Why this particular display? Why the peacock's tail? It probably doesn't hurt that full, thick hair can be a sign of health. How one styles/treats ones hair might indicate wealth---you have enough time/leisure/resources to spend time on the hair, and how you style it can also be a form of cultural signalling, which is important in a lot of situations, too. (Clothing and jewelry serve similar functions, of course).

I suspect the evolution of a long mane in domestic horses rose from a similar origin, in that a random mutation for ever-growing hair was selected for because it was deemed attractive (in this case by the horse-owners) by individuals who were able to maintain it with brushing etc. (Makes me wonder about the manes in mustangs... is there selection for shorter manes? do they cause problems for the horses by becoming tangled, dirty, etc? )

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