From a discussion thread at plastic.com:

I’m pretty sure we came when God’s alcoholism got the best of him, and he needed some money, so he invited the devil over to gamble. He said, “Here, lets take a group of these little monkeys, make em stand on two legs, and we’ll give this one a club” (a la 2001 A space odyssey.) “Lets make a bet; if they can go for 7 million years without killing themselves off, then you call off my bar tab.”

Further down the thread, there’s a Tom Waits quote: “There ain’t no devil…just God when he’s drunk.”