Are there hypotheses or conjectures that postulate any selection pressures or benefits that account for the patterns of non-pubic human hair? Particularly:
- Humans do not grow notable (i.e., non-vellus) body hair until puberty.
- Terminal body hair growth in adults is not only sexually dimorphic but also peculiar in its patterning:
As with any trait: it is quite possible that the evolution of human hair patterns had no selective significance. It could also have been the result of a sexually-selective feedback loop, and therefore are an arbitrary sex trait.
I am looking for hypotheses or conjectures that suggest some objective benefit to terminal body hair. I struggle to imagine one particularly because of the sexual dimorphism in adult hair patterns: E.g., if facial hair provides some benefit to men, why would it not provide the same one to women?
If we stipulate that the pattern is only fully expressed in males then it is still peculiar: For example, I can't see any functional characteristic that would make hair on the front torso beneficial while not conferring a benefit if present on the shoulders or top of the torso.