It seems to be that human variation is more the result of genetic drift than natural selection brought on by the environment.
For example, the migration out of africa by a group of humans 70,000 years ago may have been quite a self-selected group. It may have been a population distinct from the rest with, therefore, different allele frequencies, and thus a population that would be prone to genetic drift. It was once thought that climate change motivated the migration, but people are now linking it with innovation. So maybe it was increases in intelligence that motivated it. It could be it was a group of more intelligent humans, humans with a novel desire to explore, that left. Evidence for this perhaps comes from the fact that there was a greater number of males among them.
Although mitochondrial DNA and Y-chromosomal DNA are particularly useful in deciphering human history, data on the genomes of dozens of population groups have also been studied. In June 2009, an analysis of genome-wide SNP data from the International HapMap Project (Phase II) and CEPH Human Genome Diversity Panel samples was published.[32] Those samples were taken from 1138 unrelated individuals.[32] Before this analysis, population geneticists expected to find dramatic differences among ethnic groups, with derived alleles shared among such groups but uncommon or nonexistent in other groups.[33] Instead the study of 53 populations taken from the HapMap and CEPH data revealed that the population groups studied fell into just three genetic groups: Africans, Eurasians (which includes natives of Europe and the Middle East, and Southwest Asians east to present-day Pakistan), and East Asians, which includes natives of Asia, Japan, Southeast Asia, the Americas, and Oceania.[33] The study determined that most ethnic group differences can be attributed to genetic drift, with modern African populations having greater genetic diversity than the other two genetic groups, and modern Eurasians somewhat more than modern East Asians.[33] The study suggested that natural selection may shape the human genome much more slowly than previously thought, with factors such as migration within and among continents more heavily influencing the distribution of genetic variations.[34]
http://en.wikipedia....enomic_analysisSkin color was geographically influenced though. I read about this awhile ago...lighter skin wasn't a mutation, but the expression of a trait that had always been suppressed in Africa. and then it actually turned out to have benefits in the regions where it could be expressed (more vitamin D absorption being one of them). But so the answer to your question is probably no - black africans would probably turn more into white africans over time, not Caucasian white people
Edited by enfield, 17 April 2011 - 03:54 AM.