Why do some people have curly hair and some have straight?

Question: Why do some people have curly hair and some have straight?
- Keywords:
  hair,
  human
Asked by justinbieber to Colm, Eoin, Joseph, Lauren, Stephen on 15 Nov 2013.
- Joseph Roche answered on 15 Nov 2013:
  
  Genetics. These traits get passed on to you from your parents, so blame them 🙂

Question: Why do some people have curly hair and some have straight?