By TINA HESMAN SAEY - WIRED SCIENCE
Added: Thu, 13 May 2010 17:43:28 UTC

Thanks to Richard W. for the link.

Original link

One isn’t such a lonely number. All life on Earth shares a single common ancestor, a new statistical analysis confirms.

The idea that life forms share a common ancestor is “a central pillar of evolutionary theory,” says Douglas Theobald, a biochemist at Brandeis University in Waltham, Massachusetts. “But recently there has been some mumbling, especially from microbiologists, that it may not be so cut-and-dried.”

Because microorganisms of different species often swap genes, some scientists have proposed that multiple primordial life forms could have tossed their genetic material into life’s mix, creating a web, rather than a tree of life.

To determine which hypothesis is more likely correct, Theobald put various evolutionary ancestry models through rigorous statistical tests. The results, published in the May 13 Nature, come down overwhelmingly on the side of a single ancestor.

A universal common ancestor is at least 102,860 times more probable than having multiple ancestors, Theobald calculates.

No one has previously put this aspect of evolution through such a stringent test, says David Penny, a theoretical biologist and Allan Wilson Centre researcher at Massey University in Palmerston North, New Zealand. “In one sense, we are not surprised at the answer, but we are very pleased that the unity of life passed a formal test,” he says. He and Mike Steel of the University of Canterbury in Christchurch, New Zealand, wrote a commentary on the study that appears in the same issue of Nature.

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TAGGED: BIOLOGY, EVOLUTION, GENETICS