Evidence of earliest life on Earth disputed

When Australian scientists presented evidence in 2016 of life on Earth 3.7 billon years ago – pushing the record back 220 million years – it was a big deal, influencing even the search for life on Mars.

But that discovery, based on analysis of primordial rocks in Greenland, has now been challenged, with another team of researchers arguing in a study published Wednesday that the structures presented as proof of microbial activity were, in fact, geologically forged by underground heat and pressure.

The truth hinges on whether the cone-shaped formations in question are genuine stromatolites, layered structures left in the wake of water-dwelling microorganisms.

Previously, the earliest confirmed stromatolites were found in 3.45 billion year old rocks in Australia.

Being able to accurately date the first stirrings of life on our young planet – roughly one billion years old at the time – has important implications for understanding how it evolved.

Writing in the journal Nature, Abigail Allwood of the California Institute of Technology and colleagues concluded that the alleged fossils lacked internal layers, a signature trait of stromatolites. The cone-like shapes were shown to be ridges that typically arise through a natural deforming process called metamorphism.