Dravidian languages
Many linguists, however, tend to favor the theory that speakers of Dravidian languages spread southwards and eastwards through the Indian subcontinent, based on the fact that the southern Dravidian languages show some signs of contact with linguistic groups which the northern Dravidian languages do not. Proto-Dravidian is thought to have differentiated into Proto-North Dravidian, Proto-Central Dravidian and Proto-South Dravidian around 1500 BCE, although some linguists have argued that the degree of differentiation between the sub-families points to an earlier split.