Caste, Class and Social Hierarchy

It's a curious fact that agricultural societies, unlike hunter-gathering societies, have nearly always been hierarchical. In Wikipedia's definition,

Caste is a form of social stratification characterized by endogamy, hereditary transmission of a lifestyle which often includes an occupation, status in a hierarchy, customary social interaction, and exclusion.[1][2] Although caste systems exist in various regions, its paradigmatic ethnographic example is the division of Indian society into rigid social groups, with roots in India's ancient history and persisting until today;

Indian society has long been divided into thousands or perhaps tens of thousands of endogamous castes called jati. These are very ancient, with at least some jati having practiced endogamy for 2000 years or more. While India is the most famous example, rather analogous institutions exist or did exist very widely. Certain castes in Ethiopia appear to be twice as old (4000 years) according to genetic studies by David Reich and others. Reich notes that Ashkenazi Jews of Europe constituted a distinct caste for about 500 years. Caste like systems of social exclusion existed widely in the post-Columbian new world. Hundreds of other examples are known. Endogamy is the most crucial element of caste in our definition. The anti-miscegenation laws that were widespread in the US until the Supreme Court ended them were an attempt to develop a caste system here. My question is, what is the point of caste? My tentative answer is that it's the protection of privilege. Sometimes the privilege is socially broad, by the severe discrimination experienced by the Cagots of Spain and France, the Dalits of India, the Baekjeong of Korea, and, of course, Blacks in the US. Sometimes it's a more narrow privilege, like exclusive access to certain occupations. The modern world and social mobility has done a fair amount of violence to traditional caste systems, but new ones keep trying to form. 26% of female Princeton grads marry other Princeton grads, and 71% of college grads marry other college grads.