A vestige,certainly, but perhaps not entirely without function.
But it's hard to say. Your own post say perhaps this and perhaps that. And then again, perhaps not.
Perhaps it serves some minor function. How would we find out? We could forcibly shave off all the body hair of a million men, and compare them to ... what WOULD be the control group? Double-blind testing is right out.
It should be pointed out that there are some ethnic groups of Africans who don't have any body hair at all, not even the fine fuzz that most people have (that is, they have the normal concentrations of hair on the head, armpits, and pubic area, but none on their arms, legs, etc). I write this from memory, so I can't give a reference. I've also seen it for myself.
I read recently (I think in a book on supernormal stimuli) that the places where we do get hair are also the places where chimps get it first.
So the distribution of hair in humans could be the side effect of a (hormonal?) adaptation towards neoteny that had nothing to do with hair as such but was favored for its effect on something else, such as brain plasticity. It would be what Gould called a spandrel.
Another point to notice is that generally humans grow hair where apes do not. the face and chest are prime examples, since apes are hairless there, or sparse, but humans (especially males) grow hair in these areas.
Well I'm not sure that this is particularly sparse as compared to a human.
Sparse compared to the rest of the chimpanzee, perhaps. But to suggest that we "grow hair where apes do not" seems unjustified.
Re: Anyone disagree that body hair has sensory function?
Dr Adequate, when you brush something across your body hairs -without touching the skin - can't you feel it? I know that I can.
Yes, but I can't say that I've ever found this particularly useful.
For the purpose of alerting us to the presence of insects and ecto-parasites a whole body covering looks useful. To feel air movements and shift in breeze, likewise.
Bare skin would do just as well.
To an animal with thick fur, doubtless it is useful that hair follicles are innervated. But in us this too could be a vestige.
The sensory input from hairs may merge in our perception with what we feel from direct skin contact but I'm astonished that, even after participation in this discussion, you could think it doesn't exist. Actually I find it surprising that anyone could think that a form of sensory input that's so universal and fundamental and that they've lived with their whole lives doesn't exist.
But no-one has said that the sensory input doesn't exist. Just that it's not particularly functional.