In 10,000 years, the earth will all be water. Sea levels will have risen to cover the land, and all life will be in the oceans. Humans will have ceased to exist — or, at least, ceased to exist as we know them. They will have returned to the seas, like the whales and dolphins before them. There will still be cities, and will still be culture, and will still be all that we know to be human. But it will be based in the ocean and unlike anything we experience now.