In the Hindu social system, eight types of marriage are described. These are Brahma, Daiva, Arsha, Prajapatya, Gandharva, Asura, Rakshasa, and Paisacha. The first four types of marriages were socially sanctioned, whereas the latter four were socially disapproved.
Among the last four , the Rakshasa form of marriage was performed by abducting the bride. The question is raised, how did the practice of Rakshasa marriage start in the past? The answer to this has been provided by the British anthropologist Audrey Richards.
Audrey Richards has, on the basis of her research among Africans, pointed out that psychologists and anthropologists have often overrated the role of sex, hunger being, in reality, a more fundamental and compulsive drive than sex in exogamy, i.e., marriage outside the tribe than their own.
In hunting and food-gathering societies, food was difficult to obtain. Women and children were generally a burden in such societies, particularly those which relied more on hunting. This could have led to female infanticide, which in consequence, would lead to female scarcity. This must have led to marriage by capture and, as the next step – since such capture had to be effected from the outside tribe – to exogamy. Thus food scarcity may be, historically speaking, a probable cause of exogamy and marriage by capture.
To conclude, due to the universal fear of the strange, the novel, and the unknown, almost all the Indian tribes are endogamous.