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...
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I think the most interesting part of the article is the bit about the bacterium that converts right-handed amino acids to left-handed ones. This strongly suggests that the bacterium regularly encounters right-handed amino acids, otherwise it wouldn't have maintained those genes. But all known life produces left-handed amino acids, so where are the right-handed ones coming from? They can't just be floating around in the environment. If they were, the conversion genes would be common in other species of bacteria. So it seem like there must be a source of the right-handed amino acids somewhere.
Is that the same Paul Davies who just had a lame-assed op-ed published in the New York Times?