why do girls grow hair on their arms on legs?

Question: why do girls grow hair on their arms on legs?
- Keywords:
  arm,
  body,
  grow,
  hair,
  leg
Asked by pandaandpenguin to Mike, Pip, Tianfu, Tim, Tom on 26 Jun 2012.
- Tom Lister answered on 26 Jun 2012:
  
  Girls grow less hair than men – that’s probably a result of sexual selection. Hair offers some protection from the sun, perhaps a little from the cold. I think it’s just that we haven’t evolved that far from our more hairy ancestry.
- Tim Stephens answered on 26 Jun 2012:
  
  Humans evolved from hairier animals, and we’re closely related to monkeys where both sexes are hairy. I guess it’s a hangover from then, but girls have finer body hair than men, presumably because of some hormone that men have in smaller (or larger) quantities.

Question: why do girls grow hair on their arms on legs?