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
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.