New study argues against some of the oldest evidence for life

Enlarge / The triangular shapes had been described as possible relics of 3.7 billion-year-old microbial life. The rock has been flipped upside down since then, but the red arrow highlights that one of these triangles is not like the others. (credit: Abigail Allwood)

Few things in science seem to be as controversial as claims to the oldest evidence of life on Earth. As researchers strive to push life's origins back further into the history of the early Earth, the evidence they have is never completely unambiguous. (If you were over three billion years old, you wouldn't look so great, either.) Other scientists inevitably question any new evidence, and arguments ensue.

Microbes in Greenland?

Two years ago, a group working in the ancient rocks of Greenland stumbled on some tantalizing cone-shaped distortions of rock layers. Based on several lines of evidence, the researchers concluded that they had found stromatolites, which are layered mounds built by communities of microbes in shallow water. Modern stromatolites are mainly known from Australia's Shark Bay, but they were much more common when microbes ruled the Earth so are therefore one of the most obvious relics of life in the rock record. The Greenland find would push the age of the oldest-known stromatolite from about 3.45 billion years to 3.7 billion years.

But other researchers wanted to see these Greenland rocks for themselves. And in a newly published study led by Abigail Allwood, she and her team explain why they aren't buying it.

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