Interesting new research popping up in the news today. Darwin predicted that evolution would be a faster process in large population groups, and current science seems to be confirming those predictions with research that shows about 7% of the human genome has undergone rapid change ("rapid" in evolutionary terms being on the order of 40,000 years) under selection pressure from such civilizing activities as agriculture. For one thing, it appears lactose tolerance is a recent development, with the emergence of the LCD gene; no one, it appears, in the Stone Age could drink milk. Nor did any of them have blue eyes. Also, when people began to cluster in large population groups, thus allowing a venue for new infectious diseases to spread, we began developing genes to increase resistance to them, such as G6PD, which staves off malaria.
Today we see different alleles emerging in different population groups, unique to their continent of origin. Europeans have alleles that express fair skin, for instance, but they're different than the ones that fair-skinned Asians have. Also, it appears Asians are rapidly developing genes that suppress ear wax and body odor! Australian aborigines and African bushmen have a hard time with the grains and other carbs we in the agricultural west seem to digest just fine. This is leading to the conclusion that humans may be growing apart, not closer, as a species. In another 40,000 years, might we actually speciate? Particularly in light of the fact we all seem to be staying fertile until much later in life?
It's all nifty stuff to read (here's another article from National Geographic). And it all just shows why science is such a rewarding pursuit. Always new things to learn, to complement, refute, and/or modify existing knowledge.