Some 20,000 years ago, for example, ice sheets locked up much of the world’s water, lowering the oceans and laying bare vast coastal plains—attractive hunting grounds and harbors for maritime people. Today these plains lie beneath almost 400 feet of water, out of reach of all but a handful of underwater archaeologists. “So this shines a spotlight on a huge area of ignorance: what people were doing when sea level was lower than at present,” says Geoff Bailey, a coastal archaeologist at the University of York in England. “And that is especially problematic, given that sea level was low for most of prehistory.”

Source: Did Humans Colonize the World by Boat? | DiscoverMagazine.com