" Areas that are densely populated today, Chicago, New York, Manchester, Amsterdam, Hamburg, Berlin, Moscow -- in fact most of North America and northern Europe -- were absolutely uninhabitable due to the fact that they were covered by ice-caps several kilometers thick. Conversely, many areas that are uninhabitable today -- on account of being on the bottom of the sea, or in the middle of hostile deserts such as the Sahara (which bloomed for about 4000 years at the end of the last Ice Age) -- were once (and relatively recently) desirable places to live that were capable of supporting dense populations.
Geologists calculate that nearly 5 per cent of the earth's surface -- an area of around 25 million square kilometers or 10 million square miles -- has been swallowed by rising sea-levels since the end of the Ice Age. That is roughly the equivalent to the combined areas of the United States and the whole of South America. It is an area almost three times as large as Canada and much larger than China and Europe combined.
What adds greatly to the significance of these lost lands of the last Ice Age is not only their enormous area but also -- because they were coastal and in predominantly warm latitudes -- that they would have been among the very best lands available to humanity anywhere in the world at that time. Moreover, although they represent 5 per cent of the earth's surface today, it is worth reminding ourselves that humanity during the Ice Age was denied useful access to much of northern Europe and North America because of the ice-sheets. So the 25 million square kilometers that were lost to the rising seas add up to a great deal more than 5 per cent of the earth's useful and habitable landspace at that time. "

― Graham Hancock , Underworld: The Mysterious Origins of Civilization