As the Indian plate moved up towards the main Eurasian plate, the course of Yamuna got altered in the Himalayas moving more water of Yamuna towards the Ganga river and that of Sutlej got altered to join Indus! This caused a major loss in terms of its water source for the river Saraswati and is thought to have been the cause for its drying up. Now what does Saraswati river have to say about the Aryan Invastion theory of 1500 BC? Well, the geological excavations give a date of about 4000 BC for the drying up of Saraswati river !
Conclusion In a nutshell, the ancient vedic people were settled in India much before 4000 BC and have nothing to do with the myth of 1500 BC invasion theory! There is no separate aryan or dravidian race. There is one single ancient Indian vedic race with roots IN INDIA. Indus valley civilization is NOT the most ancient Indian civilization. It was probably only a remnant civilization of an ancient Civilization that existed till the end of the Mahabaratha war. The most ancient Indian civilization was therefore the Saraswati valley civilization (or a Ganga-Yamuna-Saraswati civilization) of the vedic age.
