Part of the show Sex Chromosomes, Genetics and Food Webs
Stuart via email asked:
I'd like to hear about recessive genes and why they say that blondes and ginger people have more of these genes and will become extinct. Why will the genes only kick in now and not before and have there been genes in the past that have timed out? Is it possible for genes like green hair to start up and replace them?
I'm not sure I can comment on the idea that blonde and ginger people will become extinct, as it's the first time I've heard that. But interestingly, some people have speculated that the Y-chromosome that we were talking about earlier may disappear completely. The Y-chromosome has degenerated during the evolution of the sex chromosomes. Some people have speculated that in 10 million years it will have disappeared altogether. Obviously that is of some concern to males, but suffice to say that natural selection will act against anything that prevented there being males within the population. So for the Y-chromosome to disappear, another gene would have to arise to make a male sex. But I really can't comment on the extinction of blonde and ginger people.