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] It is an extreme evolution of a system of legally-entrenched social classes, also endogamous and hereditary, such as that of feudal Europe. 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;[3] it is sometimes used as an analogical basis for the study of caste-like social divisions existing outside India. In biology, the term is applied to role stratification in eusocial animals like ants and termites, though the analogy is imperfect as these also involve extremely stratified reproduction.[4]