Ancestral facial hair.
Our closest ancestors, the chimpanzee and bonobo, both grow facial hair around the mouth area. What is noteworthy is that this is the case in both males and females of the species.
Female chimpanzee with facial hair:
Dichotomy of facial hair in humans.
Our own species has a notable dichotomy in facial hair between males and females. I'm interested in what broadly speaking are the theories on facial hair. Could it be as simple as sexual selection over tens, or hundreds of millennia?
A previous answer eludes to a sexual selection direction, but my question is primarily why do human females not grow nearly as much facial hair as their male counterparts? Is this just a typical sexual dichotomy? I suppose here I am interested at a molecular level - is beard growth absent, or suppressed in women?
Speaking physiologically androgen is a hormone that drives hair growth and this hormone is more prevalent in males. Although females do have vellus hair coverage on their face, the thicker androgenic hair isn't typically present. A cursory search didn't reveal to me if this is due to less follicles in the first place so androgen would have little effect, or less hormone release.
To answer the question "Why do men grow facial hair" I think three smaller questions are raised:
- What is the point of facial hair? (If there is any beyond sexual selection...)
- What selected thick androgenic facial hair out of human females?
- At a molecular level, have females lost the "facial hair gene", or gained a "facial hair suppressor gene"?