I think the easiest example (in favor of biology instead of sociology) would to compare a country like China vs a country like United States. Chinese athletes all look the same (not trying to be racist here), they all come from the same genetic heritage. But United States has people from all different backgrounds and ethnicity. So why is it that the US' track athletes are all black? It is not because white athletes were never given the chance to run, or that they looked for higher forms of sport. If you do think that there is a social explanation, then white athletes in track would have received more sponsors or opportunities. But it still stands that US' most successful athletes are black. So it's not the country's social standing or problems that create the skewed results.