Outbred

I'm not sure I beleive this study's findings - since most kids you ask often confuse family county of origin and race. But it seems like natural selection to me. The people who prioritize their personal financial and social success are busier and thus have less time for children. The people without that particular work ethic have more time on their hands to have and raise children. Eventually the successful are out bred by those who put family and the future first.