Why do we grow hair on our heads and eyebrows?

Question: Why do we grow hair on our heads and eyebrows?
- Keywords:
  eyebrow,
  hair
Asked by rebecca.leyland to Huma, Jack, Lucy, Miranda, Peter on 14 Nov 2016.
- Peter Boorman answered on 14 Nov 2016:
  
  I’m not really sure! Great question though – perhaps we grow hair on our eyebrows because our ancestors needed eyebrows to protect their eyes from tough conditions, such as weather?
  
  Peter

Question: Why do we grow hair on our heads and eyebrows?