Why humans have so little hair compared to other apes

Originally published at: https://boingboing.net/2018/12/11/why-humans-have-so-little-hair.html


This theory never made any sense to me. Apes don’t usually have much hair on their faces, and bearded humans actually have MORE facial hair than many apes.


You haven’t met me then…


The problem with this is that there are plenty of good evolutionary examples of the former (i.e. hippos), but none of the latter.

I’m sure there are better reasons to prefer one over the other, but I’ve never heard them expressed in laymen’s terms.

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lolwut dog

srsly cat


We aren’t really that hairless.

"Less attention has been paid, though, to the fact that humans are not really hairless at all. Per square centimetre, human skin has as many hair follicles as that of other great apes. The difference is not in the number, but in the fineness of the hair that grows from those follicles. "


Do we know when humans lost our hair human hair became so fine?

There is a suggestion about fire/clothing in there. But if we only became so much less hairy after we developed fire then that goes to another theory I’ve heard bandied about that what we call a human is a product of technology and never existed in a “natural state”.


A more widely accepted theory is that, when human ancestors moved from the cool shady forests into the savannah, they needed better thermoregulation. Losing all that fur made it possible for hominins to hunt during the day in the hot grasslands without overheating.

Ahem: lion, giraffe, zebra, antelope, cheetah, etc. The elephant is hairless, but it seems like more savanna animals are hirsuit than glabrous.


Millar says there are some obvious reasons—for instance, having hair on our palms and wrists would make knapping stone tools or operating machinery rather difficult, and furry foot soles would constantly get sap, acorns and cigarette butts caught in them.

Okay, I’m sorry, but I already dislike this article. That might be vaguely interesting…if we hadn’t just established (and should, of course, already know) that all primates, and pretty much all mammals, share the same trait.

Evolutionary scientist Mark Pagel at the University of Reading has also proposed that going fur-less was a way to control lice and other parasites. Humans kept some patches of hair, like the stuff on our heads to protect from the sun and the stuff on our pubic regions to retain secreted pheromones. But the more hairless we got, Pagel says, the more attractive it became, and a stretch of hairless hide turned into a potent advertisement of a healthy, parasite-free mate.

Yeah, that worked out great. Now humans are special in the animal kingdom for supporting two different species of lice: one for our heads and one for our bodies. And that’s not even going into varieties crotch crickets.

One of the most intriguing theories is that humans lost the hair on their faces and some of the hair around their genitals to help with emotional communication.

As @Brainspore points out above, this is not so much speculative or controversial as just baldly untrue.

But our third cone is unusual—it gives us a little extra power to detect hues right in the middle of the spectrum, allowing humans to pick out a vast range of shades that seem unnecessary for hunting or tracking.

Bdaaagh! Again, total fucking bullshit. We have color discrimination because we share it with all of our hair-covered primate relatives, who need it because they are largely frugivores or transitional herbivores who need red/green distinction to assess the ripeness of fruit and the toxicity of leaves. Was this published on April first, or is this a proud graduate of the Pat Robertson College of Biology?


This is the most convincing argument I have heard about hairlessness and sweat glands. In the absence of teeth and claws, we developed the ability to literally run our prey to death, and to do so in the heat of the day when most other predators are waiting it out in the shade. It makes logical sense, but since behavior does not fossilize, it remains a hypothesis that is pretty difficult to test.


While some have much more than others.

It’s a distribution problem. Typical.


Me, I always thought a bit of column a, a bit of column b made sense. Still sweat as an edge when hunting/harrying prey seems like the biggest reason to me. And yes, I admit I was once swayed by The Science of Discworld where I first read of the aquatic ape theory.


I had this conversation with my SO the other day. Tongue firmly in cheek.

“You ever notice how un-fuckable really hairy guys are? Applies doubly so to women. Well generation after generation the less hairy ones fucked more and here we are mostly hairless.”


Except that hunting dogs and wolves do pretty much the same thing.


Why? Style, baby. Style.


The funny thing is that I don’t think we can entirely rule that out. I recall an experiment done with some kind of bird (peacocks?) where they put different coloured leg bands on the male birds to see how it affected mate selection (females select their mates) and it made a huge difference. Like a previously way-down-the-ladder guy was suddenly top choice if he was wearing the right colour.

We might say that evolution would tend to weed this sort of thing out, but evolution isn’t an omniscient god, it’s just A/B testing. And A/B testing moves you towards local maxima, it doesn’t do what’s best overall. Maybe we really do have fine hair just because that’s what we find more attractive on average, and we find it more attractive on average because of an accidental confluence of systems that were designed to look for other things.


… or still does?

Fuzzy Wuzzy was a bear
Fuzzy Wuzzy had no hair
Fuzzy Wuzzy wasn’t fuzzy – was he?


In savanna conditions a fit human can cover more distance than a dog without pausing for rest, though dogs generally have humans beat over short distances.


Old Man Dingo to the contrary, most predators are sprinters. Fit humans, as it turns out, are marathoners.