Life Can Go On for Billions of Years

I believe that life can go on forever. It takes a million years to evolve a new species, ten million for a new genus, one hundred million for a class, a billion for a phylum—and that's usually as far as your imagination goes. In a billion years, it seems, intelligent life might be as different from humans as humans are from insects. But what would happen in another ten billion years? It's utterly impossible to conceive of ourselves changing as drastically as that, over and over again. All y...