“An argument could be made that mixed-race families are maladaptive — both for the parents and the children — and undermine one’s genetic interests. As noted by various commenters, multiracial families often do not possess the harmony, cooperation and purposefulness of same-race families, because mixed-race families lack the focus of genetic investment and returns that same-race families possess.”

SocioBiological Musings: Biological Problems with Mixed-Race Families, Marriages Relationships & Adoptions