If you are a pre-history buff like me, you'd have wondered what explains the sudden appearance of agriculture, brick buildings, stone masonry and indeed, language and culture in the 4000-5000B.C era. How is it, that agriculture started simultaenously around 4000BC in places as far away as Sumer, the Indus-Saraswati valley and Japan? And if you are interested in mythology, you'd wonder about the persistence of an all-consuming mega-flood that is supposed to have ended known civilizations in Hindu, Sumerian, Judeo-Christian myth, as well as in the story of Atlantis. The flood in which India's Manu, Sumer's Zisudra and more popularly, Israel's Noah constructed arks or boats that protected important knowledge and lifeforms during the flood, and released them again to recreate and repopulate the Earth. You'd have heard of theories that extended from the bizarre (alien contact that gave humans technology) to the plausible (sudden inventions that changed lives drastically).
And finally, if you are interested in Indian history, you'd wonder about the Aryan invasion, about Sanskrit's European origins, and the reasons behind the downfall of the Indus-Saraswathi civilization.
Well, after a long while, I finally started reading the book "Underworld" by Graham Hancock, and it makes a very serious attempt to provide some answers. Using inundation maps of the last Ice Age (wiki, video, earth info), Graham examines the truth behind the various myths. For instance, underwater stone blocks have been found off the coast of Gujarat at the location where the mythological Dwaraka was supposed to exist. According to the sea depth, and inundation maps, Graham estimates its date to be around 7000BC, far earlier than the 4000BC when Indian civilization was supposed to have started. Making use of various geological techniques that predict three super-floods at various ages, Graham makes the case for a single or many post-Neolithic civilizations, that built these (now underwater) cities, that were ravaged by floods caused by the Last Global Meltdown. For instance, it is a theory that the Hudson bay in Canada was a freshwater lake during the Ice Age, whose walls broke down to release millions of kilometers of freshwater into the Atlantic, around the same time when Plato said that Atlantis sunk. With critical looks at underwater, overland, mythological, cartographical and scientific evidence, Graham propounds his theory - that the Pyramids of Egypt, the Stone henge of England, the drainage system of the Indus valley, Siva worship in India, the Vedas, all evolved either at a much earlier time than accepted today and/or were preceded by a period of learning that is lost to us today.
A good read. Although at 700+ pages, it is quite long.