Andites migrated into valley of Ganges about 15,000 B.C. during 1,500 years. 
Ancient India acted as a catch basin for the migrating races. The base of the peninsula was formerly somewhat narrower than now, much of the deltas of the Ganges and Indus being the work of the last 50,000 years. 
The Dravidian centers of culture were located in the river valleys, principally of the Indus and Ganges, and in the Deccan along the three great rivers flowing through the Eastern Ghats to the sea. 
On the Gangetic plain Aryan and Dravidian eventually mingled to produce a high culture, and this center was later reinforced by contributions from the northeast, coming from China. 
Marine animals of primitive ages took temporary refuge in three favorable retreats: the present Gulf of Mexico region, the Ganges Bay of India, and the Sicilian Bay of the Mediterranean basin.