Because natural selection doesn't have a huge affect on us anymore. The more advanced we became the more "less suited" individuals could survive. Also we have you notice how an African native looks nothing like a Native American or how they both look dramatically different from a Scandinavian. There has been evolution occurring since the first "humans" evolved. But I can tell you that Hominids have been around a lot longer then 10,000 years. That sounds more like when homosapien (humans and a number of other subspecies whom died out) first appeared.