Caucasians and Mongoloids live in the same latitude. Supposedly environment is the cause of evolutionary drift. Cold is supposed to lead to prominent (European) noses. Why don't the Asians have prominent noses. It snows there too. Their noses are more like African noses, the noses of a hot climate. Another problem I have with genetic (evolutionary) drift is pigmentation. Asians are darker than whites, yet they get about the same amount of sunlight, the supposed cause of melanin which colors the skin. Somehow I think the evolutionary process, genetic drift, and an out of Africa theory needs more work.
The drift between the major races is great. The apparent time span is equally great. The idea that the races were isolated for such a long time troubles me. I would expect that the nomadic life of early man would have led to greater intermingling among the races, especially in Eurasia, and a more blended result.
The drift between the major races is great. The apparent time span is equally great. The idea that the races were isolated for such a long time troubles me. I would expect that the nomadic life of early man would have led to greater intermingling among the races, especially in Eurasia, and a more blended result.
The answer to that is that evolution does not occur in response to a change in environment. Evolutionary changes are random. If a change confers an advantage in a particular environment, organisms with that new trait will have a survival advantage over organisms without it, and they will reproduce faster. If we see a trait that confers an advantage in one population, but not another that lives in a similar environment, we can assume the mutation only happened in one population. There is no reason separate populations would have the exact same mutations.
Early humans might have been nomadic, but they never traveled far from their birthplace. So, even groups a few hundred miles apart might have become genetically quite distinct from each other. With modern travel and intermarriage, some of those genetically distinct groups are disappearing. I read of one population in Japan that only has a couple of dozen members left, because everyone else married outside of the group.