This concept of women marrying up, cited in the Smritis as the Anuloma, was justified as the mechanism to keep the Hindu ideological equivalent of the gene pool from degrading. The opposite of the Anuloma, called the Pratiloma, was not allowed in the ancient Indian society. However, the Mahabharata cites examples where exceptions were allowed, as for instance when Devayani, the daughter of Shukracharya, married the Kshatriya Yayati.