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Several years ago, a grouping of researchers revealed a new fossil discovery suggesting that life on Earth started even earlier than we thought. The 3.vii billion-twelvemonth-old structures found in Greenland certainly looked like they had a biological origin, but a new study casts dubiousness on the original claims. A different team says the structures identified in Greenland are most probable just rocks. Technically, fossils are rocks, only the question is whether they used to be alive.

The original team uncovered unusual cone-like structures in the Isua supracrustal belt in Greenland, dating to 3.vii billion years in the past. At the time, the researchers concluded that these shapes were about likely "stromatolites," modest clusters of single-cell organisms and biofilms that fossilized. If true, that would push back the earliest evidence for life on World by hundreds of millions of years. The next oldest fossils are from the Strelley Pool Formation in Commonwealth of australia, which date from iii.45 billion years agone.

With fossils this old, there'south not much yous can do to differentiate them from surrounding rock on a chemical level — there's no Deoxyribonucleic acid or protein to confirm without a dubiousness that this structure used to exist alive. However, the morphology of the fossils tin can tell you a lot. The Greenland find does look like newer fossils of single-celled organisms, and the rare-Earth element limerick didn't dominion out life.

The new analysis led by NASA astrobiologist Abigail Allwood looked at the 3D shape of the rock features rather than merely the exposed surface. Allwood was involved with the discovery of the Australian stromatolites that are the currently oldest accepted show of life, and she's unconvinced by the Greenland observe.

Samples identified in the original study as fossils. Via Nature.

On the cease, they do look like biological stromatolites. Notwithstanding, the latest study says that's just a cross section of elongated triangular tubes. In addition, some of the structures were upside downwardly, which doesn't make sense if they were growing upwardly from an ancient seabed, as the previous team had surmised. That is definitely not something nosotros would expect from fossils in of this historic period. Allwood also ran the samples through a prototype instrument called PIXL that will go to Mars on the 2022 rover. This test showed the rocks don't take the distinctive lamination layer pattern y'all'd look from microorganism fossils.

The team puts forward a number of geological explanations for the structures that don't involve living organisms. Substantially, sedimentary rocks could take been warped by extreme pressure to take on a tube shape. The original researchers strenuously object to the new assay of their work, saying the analysis was conducted on the wrong samples. This is science. Someone is either going to confirm the original study or the new one. We'll simply have to look and come across.

At present read: The Oldest Rocks on Globe Could Contain Signs of Life, Oldest Fossils Ever Found Dated to iii.five Billion Years Ago, and Silurian Hypothesis: What If Humans Aren't the First Civilization on Earth?