Whenever species are subjected to changing, or differing, environmental influences, natural selection will take place. If there are a lot of storms, the bones of birds will grow measurably stronger. If there are few storms, they will grow thinner. Cancer and malnutrition take differential tolls depending on the influence of the Sun. If there is insufficient sunlight, human skin will grow lighter. If there is too much, skin will grow darker. It doesn't take a million years. The soldiers of World War II were descended from parents who survived the Spanish Influenza in 1918. There was no similar epidemic in 1945.
Every dimension of human habitat may well have some sort of effect, not excluding self-generated dimensions. The baby boomers were descended from men who survived World War II -- and those who remained at home. The aspects of young men that may have caused them to be classified as 4-F are probably represented today at a higher frequency than they were before the war. Such things can change in a single generation.
Nicolas Wade has a review of current genetic research in the NY Times claiming that 700 regions of the human genome show the effects of natural selection over the last 5,000 to 15,000 years. Considering that our environment has changed dramatically due to the creation of agriculture and cities, not to mention all the other concomitants of civilization, can this be surprising? The punch of the article comes from the assertion that some of these changes appear to differentiate racial subgroups. Human induced selection of domestic animals has certainly created much greater changes than any apparent or postulated racial differences. Let's not flinch from the truth, whatever it may tell us. The Truthsearch Meme, applied consistently, will engender satisfying expansions of Complexity.
(Link provided by Andrew Sullivan.)
3/9/2006 3:15 PM