It is thought to have differentiated into Proto-North Dravidian, Proto-Central Dravidian and Proto-South Dravidian around 500 BC, although some linguists have argued that the degree of differentiation between the sub-families points to an earlier split. The only book which covers all the Dravidian languages which can point to Proto-Dravidian forms is Dravidian Etymological Dictionary still consist only of lists of related words without further explanation; therefore for a talented linguist Proto-Dravidian offers large possibilities.

Differentiation
Historical phonology
Reconstructed language
Homeland