They believe that the various groups could have arisen only by evolving separately over tens of thousands of years. However, as we shall see, this does not follow from the biological evidence. Modern genetics show how, following such a break-up of a population, variations in skin color , for example, can develop in only a few generations. There is good evidence that the various people groups we have today have not been separated for huge periods of time. Scripture distinguishes people by tribal or national groupings, not by skin color or physical appearance.
All peoples can interbreed and produce fertile offspring.
In fact, the DNA differences are trivial. The DNA of any two people in the world would typically differ by just 0.2 percent. The variation in DNA between human individuals shows that racial differences are trivial. This genetic unity means, for instance, that white Americans, although ostensibly far removed from black Americans in phenotype, can sometimes be better tissue matches for them than are other black Americans. Within each classification, there may be many different sub-groups.