• Question: How does evolution explain that men have beards yet women don't?

    Asked by happylordsteambath to Emma, Jimmy, Janet, Niall, Simon on 12 Mar 2013.
    • Photo: Niall Crawford

      Niall Crawford answered on 12 Mar 2013:

      hmmm good question. There may not be an evolutionary advantage to it, rather that somewhere in human history there was sexual selection by males to choose females with less facial hair, and by females for males with facial hair. Of course, men tend to get more hair in other places too – on the back, the chest, the arms and the legs, so these may have been chosen too. Lots of animals have sexual dimorphism (where the males and females look different in the same species), so maybe this is some form of that.

    • Photo: James Holloway

      James Holloway answered on 12 Mar 2013:

      So I think Niall has got it here.

      I’ll add a bit about why people grow hair:
      Hair that doesn’t grow on the top of your head is triggered by a hormone in your blood called testosterone. Both men and women have it, but men have 7-8 times more.

      Testosterone tends to make people more aggressive, dominant and physically bigger. Maybe in the past men that were bigger and more dominant were chosen more often by women? And the little nicer men were not.

    • Photo: Emma Ashley

      Emma Ashley answered on 12 Mar 2013:

      Yep, and also maybe the women who did have higher levels of testosterone and had beards early in evolution were not as attractive to men and were selected out of the population?

      Even nowadays, if women have hormone imbalances with a higher level of testosterone than normal, facial hair can grow. However, this is often treated (we measure these hormones in the lab!)

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