Graham hancock’s Lost civilisations was shown on the discovery channel recently. Graham hancock apparently is the proponent of a thoery that, the civilizations thrived around the world during the last ice age. The end of ice age and the resultant rise in the sea level, saw their desctruction. The end of the last ice age is linked to the occurance of flood in all the leading myths around the world.
In the programme he verifies the possibility of a bygone civilisation, now under sea, in the gulf of cambay(off Gujarat coast). Recent discoveries in that area using marine technologies show possible existance of two large prehistoric sites below sea. Some of the materials recovered from the sea, has been dated to around 6500 BC with carbon dating method. But this need to be confirmed conclusively. [link]
With the current archealogical evidence, human civilisation in the indian subcontinent began with the indus valley civilisation. German scholar max muller proposed the theory of aryan invasion, where the nomads orginally from europe invaded the region of Iran and India, pushing the deemed dravidian civilisation of the Indus valley. They are, as per the Aryan invasion theory the beginners of vedic civilisation.
This theory was widely accepted, and is still taught in most of the academia. This theory started to crumble as there was no clear evidence of any massacre or invasion as such of the Indus valley civilisation. This eventually gave way to the Aryan migration theory, where over a period of time the Aryans moved to Indian subcontinent and forced the dravidians south. These still remain thoeries as the evidence to conclusively support them is still missing.
On the other hand recent geological and archealogical discovery has done more to shake the foundation of the Aryan invasion theory as well as the Aryan migration theory. The evidence of existance of a long dried up river through the present day Rajasthan and Gujarat, has given birth to the theory of Saraswati valley civilisation. As per this theory the vedic civilisation thrived on the banks of river saraswati, and the indus valley civilisation is the last link of that civilisation. An interesting debate is brewing between the Aryan invasion theory and the Saraswati valley civilisation theory.
More archealogical discovery needs to be done before conclusively establishing the history of the subcontinent. But its interesting to note that the leftists and the right-ists have already taken sides in this theories conflict. Unfortunately it seems like that the history will be written based on the idealogies rather than based on the scientific evidence.