Weird Life: Pass the Arsenic, Please

A couple months ago, I wrote a feature for Discover about the intriguing possibility that life might have originated more than once on Earth--and that maybe those alternative life forms were still alive among us today. Paul Davies, one of the scientists who has explored this idea in recent years, has written an account of it that's the cover story of this month's Scientific American. Check it out. Davies offers some neat possibilities, such as the notion that living things might use arsenic instead of phosphorus to store energy. One creature's poison...