Some people have straight hair, some people have curly hair, and some people did terrible things to their hair in the 1980s. The kind of hair you're born with is a roll of the genetic dice, but science has learned some interesting things about the subject over the years.
For instance, curly hair is the result of hair follicles on the scalp that are asymmetrical, causing hairs that are not perfectly round in cross section. The reason curly hair tends to frizz more – well, one of the reasons – is that the natural oils secreted by the scalp have trouble moving down all those loop-the-loops. Trace Dominguez has more improbably intriguing details in today's DNews dispatch.
Scientific American: Straight Hair Is Knottier Than Curly Hair
NY Times: East Asian Physical Traits Linked to 35,000-Year-Old Mutation
Time: The Physics of Curly Hair-Because You Deserve to Know