Endogamy and the Control of Marriage and Mating
It was the caste system, through the practice of endogamy – essentially state regulation of people’s romantic choices over the course of centuries – that created and reinforced “races,” by permitting only those with similar physical traits to legally mate. … Endogamy ensures the very differences a caste system relies on to justify inequality.
Isabel Wilkerson, Caste: The Origins of Our Discontents