The use of biological explanations to justify the privileges of the dominant group is the swiss army knife of ideology in human societies. Whether or not some group distinction is "really" based on genetics is irrelevant; the crucial thing is that people in a given social context are taught that the social differences are due to biological differences, with the dominant groups inevitably possessing the "superior" traits.
--One relevant example we've kicked around on LBO before: the Herrnstein and Murray Bell Curve stuff. "Why are those people poor? They lack the heritable trait that the wealthy cognitive elite possess!"
Miles