Hair Color

LOL....and I was about to post on genetics and dominant genes......

But I like Cywr's answer better.........

 Interesting question. The reason for that is that actually the gene for various hair colour exist in even people like the chinese but they usually occur in pair with another dominant gene and therefore their effect are inhibited. In europe however, their is the possibility that the small group of people carrying the inhibited gene for say blonde hair (yep blonde chinese do exist, and I'm not joking but they are rare just like red hair african) might be more adapted to early european environment. For instance they might produce more vitamin D, vitmanin D is very important for the bones . Eventually they survived ,they breed and their gene become more frequent, despite being not dominant their this genes are favoured by the european landscape.  Now imagine this process take thousands of years, therefore a race is change into another without even any mutation, it's just the genes that was previously inhibited in the original population become increasingly more frequent in the new population. Here the environment is essentiall.