Most apes bodies are completely covered in hair with the exception of their faces; humans being the exception with only very fine hair on their bodies  while adult male humans grow thick facial hair, in particular moustaches.  I imagine heat, clothing, etc may have caused humans to lose their body hair in the course of evolution but I'm intruiged about why we gained a moustache.

Relative to the hair on my head, my beard appears to be rapidly greying. In fact, it's very rare that a grey hair from my head shows up. However, my beard is going to "salt and pepper" quickly. Aside from the fact that there's less hair per square inch of skin on my face than my head, is there a specific reason for this?