Most mammals seem fine with shorter hair (usually denser though). The only other case that comes to mind of very long hair restricted to a specific body area is that of horses manes, which to be fair I’m also not totally sure what purpose it serves. Many equines seem fine with shorter manes and tails that don’t have such long hair, like zebras. They swish flies away all the same.
Some animals have long hair but it covers most of their bodies (like llamas or yaks maybe), it’s not restricted to a small area. Other animals have denser or longer hair in some areas, like lions, but this serves a purpose (protection of the neck and head) and even then the length ratio between these longer hairs and the rest of the fur isn’t as skewed as that of humans.
So, why? I get that hair on the head helps protect it from the elements and sun, but why so long? Some humans can grow hair longer than their own body length, which is remarkable, and without doing any fact check I’d say we are probably among the top 5 species with longest hairs ever. Is it just a showoff feature like a peacock’s tail feathers, an indicator of overall health? Or does it serve another function as well?
I didn’t mean to type this wall of text…, thanks for coming to my TED talk
Something doesn’t have to be an evolutionary advantage to persist in a population. If long hair doesn’t impact fitness then it won’t get selected against.
Long hair could also just be a sign of fitness in the same way colorful feathers are for some birds.
I think many see evolution as a smart process moving towards something or as improvement. That’s correlation, it looks that way from the outside, but evolution is merely what survived long enough to reproduce most, and traits best for that and/or selected by a partner, are what get passed on.
And back to OPs question : maybe long hair was helpful? Either in finding a mate or keeping warm.
I’m bald AF though, and successful on both counts so what do I know?
You aren’t subject to every pressure every hominid ancestor ever was. Bald today still gets you laid, congrats! And you got hats to keep warm and look fabulous. :) I believe long hair must have presented some kind of advantage at some point though, there are some interesting comments here.
Yes, I understand this and it is in my post as part of the question: is it just a showoff feature like peacock’s feathers? I also understand traits that don’t impact fitness won’t be selected against.
But I have the nagging feeling that the body does spend a fair amount of extra resources creating long hair when it could make do with just a fraction. Use it or lose it is a popular trend in the animal kingdom. You can have a very showy coat using a lot less resources, if we’re talking about health markers only.
But, fear not, there are theories that support long hair as having an actual practical function that impacts fitness, and people in the comments have posted some.
What I like about these theories is that they aren’t mutually exclusive. You can have a variety of factors that mildly favor the same trait, it’s not always one single factor exerting clear pressure on things.
I’m not sure it’s the primary reason long hair evolved in humans and I’m not a scientist, but I do know that you can use it kind of like handlebars/reins when you’re hitting it from behind. Only with their full, notarized consent, obviously.
Just more evidence of the Grand Design!
Checkmate, atheists!
Well… More to my point… That means it’s a liability, right ?because that’s all fine and dandy when consensual but over the course of history more people have died as a consequence of getting caught by the hair than the offspring such long hair ever facilitated. I mean most military forces cut their hair for a reason. But I’m neither a scientist or a soldier so, I could be wrong too.
Humans evolved with dense curly hair, which protects you from the heat https://www.psu.edu/news/research/story/life-air-conditioning-curly-hair-kept-early-humans-cool
Oh yeah, and if you have really curly hair, it is effectively shorter
Yes, that’s very interesting, and I also read about similar studies which explain pubic hair texture as having moisture isolating capabilities. However this doesn’t address my question, which is about the apparently excessive length of head hair regardless of texture.
It does. Curling up makes the hair effectively shorter. And keeps it closer to the head.
A built in sun hat.
There are two different things coming into play here.
First of all, hair length evolved before long hair did.
Modern humans originally evolved tightly curled hair. Basically like we still see in many African populations. It’s thought that this was an adaptation to protect against the heat of the sun. Basically like an insulated sun hat. The longer this curly hair grew, the more protection our natural hat provided.
As homo-sapiens populations moved further North, this protection was no longer needed - in fact there was the opposite problem, it was cold and rainy.
Greasy straight hair offers an advantage over curly hair in this kind of environment. It acts like a waterproof blanket, preventing the skin beneath getting wet, and it dries more quickly. Heat is lost through wet skin significantly faster than dry skin, and in situations where energy sources might be hard to come by in winter months, this can be a disadvantage.
We already had hair length sorted, so it was simply a matter of reacquiring the straight hair shape.
Europeans got a leg-up in this regard - Neanderthals appear to have had straight hair, and interbreeding definitely occurred. At this point it’s worth remembering that by the time anatomically modern humans evolved in Africa, earlier hominids were already living all over Africa, Europe and Asia. Neanderthals were very similar to modern humans and shared an extremely close common ancestor.
And this is how, and why, some homo sapiens populations have long straight hair.
Aha, this answer is satisfactory. You introduce the concept of greasy long hair. At first I thought, well why not just greasy fur then? Why only on the head? But then I remember humans and probably early hominids like to wrap themselves with things like other creatures pelts and the head is probably the only place you can actually grow hair from. And if greasy it’s like a sort of raincoat thing.
I can sleep now thanks
Demonstrates health history and general safety over the last potentially many years, which is good for status and attracting mates. The capacity to shear hair once stood as a statement of technological capacity and combat effectiveness: “I have a sharp knife.”
Alright, that’s true with the history since long hairs stay for years, good point. I’m not sure I follow with shearing and technological capacity, mind explaining that a little bit more please?
If you have a shaved face or cropped hair, it means you have access to and are possibly carrying a sharp blade. For a million years, that was high tech. It indicates that not only are you dangerous to fuck with, but you also probably have other advanced technology and culture.
I’m not claiming this is an evolutionary reason, I just think it’s interesting.
That’s an interesting take, agreed. But it doesn’t explain why the length… You can still shave hair that doesn’t grow too long. And look dangerous to fuck with
Yes, that is not an evolutionary pressure. Long manes serve the same function in humans as a peacock’s tail or a baboon’s bright red ass.
Doggy style
We do lose most of our heat from the head, so the original purpose might have been insulation
The notion that we lose most of the heat from our heads comes from a study where people wore warm clothes and no hats…
oh, interesting! Can I have a source please? I love learning new things!!
Why do we get an advantage from hairs longer than 60cm? 20cm already does the job, it even covers your neck.
mate selection, almost entirely. it’s sensitive to body condition to the extent that if a woman sees the same hairdresser consistently enough they can somewhat reliably tell if she’s gotten pregnant. it’s also an easy indicator of social class and stability ie: do they have the time and resources to take care of it?
Funny idea what if its a remnant from the early tool use era where hair was used to make all sorts of stuff and people that had more long hair could do more stuff which increased their survival chance? Pretty sure thats nonsense but it would be funny imo
Heh that’s an interesting consideration. I also wondered about this. It’s not mutually exclusive with other theories, so…
There is the fun aquatic ape hypothesis. It’s a fun one, along with the stoned ape hypothesis. But unfortunately there’s not a lot of actual evidence for either of them.
TLDR I, specifically, look more fabulous
