Growing Red-haired Kitten

Harding et al. (2000) proposed that red hair was not the result of positive selection but rather occurs due to a lack of negative selection. In Africa, for example, red hair is selected against because high levels of sun would be harmful to fair skin. However, in Northern Europe this does not happen, so redheads come about through genetic drift.
Estimates on the original occurrence of the currently active gene for red hair vary from 20,000 to 100,000 years ago.
A DNA study has concluded that some Neanderthals also had red hair, although the mutation responsible for this differs from that which causes red hair in modern humans.