Comet Enthusiast

"At first, evolution proceeded by natural selection, from random mutations. This Darwinian phase, lasted about three and a half billion years, and produced us, beings who developed language, to exchange information," according to Stephen Hawking, our planet's preeminent physicist.

But what distinguishes us from our cave man ancestors is the knowledge that we have accumulated over the last ten thousand years, and particularly, Hawking points out, over the last three hundred.