(9 of 9)
That's not to say humanity can't become extinct. A 50-mile-wide asteroid crashing down from space would do it. So could a sudden and thorough collapse of earth's ecosystem through pollution, deforestation and the like--unless we establish some colonies in space beforehand. But whatever happens, the long history of multiple hominid species struggling for supremacy on earth is over. After millions of years, evolution by natural selection, operating blindly and randomly, has produced a creature capable of overturning evolution itself. Where we go from here is now up to us.
--With reporting by Martha de la Cal/Lisbon, Peter Hawthorne/Cape Town, Edward Owen/Madrid and Simon Robinson/Addis Ababa