moominmuppet

Right; I think that's exactly what I'm arguing in my first long reply; in the case of red hair, it's a small percentage of the population that carries it. As they and their descendents spread move evenly across the globe, the odds of them having offspring with that particular double-recessive drop. I think eventually you would get to a point where seeing a natural redhead is a very rare and unusual occurrence. It only build to the frequency it did because of genetic drift among small, isolated populations.