"If life did happen many times, there could be something like a shadow biosphere that either was, or is, all around us," Arizona State Univeristy astrobiologist Paul Davies said here Sunday at the American Association for the Advancement of Sciences meeting. "It's entirely possible that some fraction of microbial life could turn out to be alien or 'weird' life as we prefer to call it."

Davies' contention challenges the relatively accepted orthodoxy that life arose once on Earth and colonized the entire planet. This weird life would the best possible analog for extraterrestrial life. Finding it, or even creating it in a laboratory, would give researchers clues about both how life began on Earth and how common life is on other planets. If a second sample of life on Earth exists, it would raise the probability for extraterrestrial life and help provide knowledge about other plausible structures for life in the universe.