Thus we thought this was an attractive area in which we could apply some molecular tools to further clarify the history of human evolution in India. A fifth varna, the Panchama, was added at a later date. Religious rights, material resources and education, and occupational specialization were, and remain, largely determined by caste status. This hierarchy is maintained by law, ritual and religious philosophy. Each caste represents an endogamous.
Marriages occur primarily between individuals of equal status.
Men from a higher varna may occasionally marry women of a lower varna, and this is an accepted marriage. Marriage of men from a lower varna to women from a higher varna is strictly discouraged. This sets up a specific model of gene flow through the caste system, such that women are much more likely to move from a lower caste to a higher caste, with more gene flow occurring between castes which are adjacent to one another. However, men are relatively fixed within each of their caste levels. This model has been of longstanding study by many social scientists, and given that Hindus comprise approximately 80 percent of the population of India, or nearly one billion people, it was also of interest to population geneticists like ourselves.