The recent demonstration by Trautmann and Tyler of a distinction between North and Central Dravidian and South Dravidian kinship terminologies--the former having alternate generation equations, the latter not--left unresolved the problem of deciding which situation was present in Proto-Dravidian. With the help of other data and some recent theory, it is shown that this equivalence is just one expression of a principle of alternation underlying the social organization of most central Indian tribes and of certain similar societies in other parts of the world. It is argued that this principle has mostly disappeared in south India, suggesting that it is North and Central Dravidian that most closely represent Proto-Dravidian in this respect. The article attempts to explain and redress the relative neglect of alternate generation equivalence in recent anthropological theory, despite the fact that it is as significant as the cross-parallel distinction in the kinship of many societies.