In 2016 it was announced that the thaw in Greenland had uncovered remains of the oldest known living being. It was not a threatening virus, nor a dangerous alien, but a small collection of conical piles of sand that had been fossilized in the Isua formation, with an age of 3,700 million years. According to its discoverers, they were stromatolites formed by microbes that fed on sediment at the bottom of a shallow ocean. The investigation, published in Nature, opened up endless questions about the origin of life on Earth and other planets, and what other surprises may arise from the ice due to climate change.
Today, the surprising find falters, but not without confrontation. A second team from the US and Denmark has traveled to Greenland to carry out an independent study of the rocks of Isua, northwest of the island, and comes to a very different conclusion. The supposed stromatolites, a few centimeters high, were actually formed by geological phenomena unrelated to living beings, explain in your study, also published in Nature. Thus, the remains of the oldest living beings in the world would continue to be the stromatolites of the Pilbara Craton (Australia), with an antiquity of 3,450 million years. It is no coincidence that this new study is signed by the team responsible for the study of Australian fossils, led by Abigail Allwood, of NASA's Jet Propulsion Laboratory.
The new study provides evidence that the alleged Greenlandic stromatolites do not have internal layers characteristic of these formations. In addition there is evidence that its pyramidal shape is not due to the action of microbes but to the pressure suffered by the rocks to be deformed by the pressure and temperature of geological processes "very later" to the age of the original rock. The work also uses the PIXL x-ray instrument to analyze chemical compounds in the rock, which will be mounted on the exploration vehicle that NASA will send to Mars in 2020. In fact, the authors of the study say, the case of the remains of Greenland is a warning of how difficult and deceptive it can be to find traces of life on Mars.
The authors of the original study do not accept the conclusions of their rivals. Allen Nutman, of the University of Wollongong (Australia), says that his samples do have an internal structure, a flat bottom and an irregular peak that points to the formation of microbes, in addition to carbon isotopes that indicate that the cones were formed in a marine environment. "We remain in our interpretation," he concludes.
At the center of the controversy is the difficulty – if not impossibility – of finding conclusive evidence of life on rocks over which millennia have passed based only on their form, says Mark van Zuilen, geomicrobiólogo of the Diderot University of Paris, in a commentary to the study. In his opinion, Allwood's study presents "strong evidence that the rock has physical deformations and therefore that the structures it contains do not have a biological origin".
"At the moment it is not plausible that these structures have been formed due to the action of life," agrees Juli Peretó expert in Evolutionary Biology at the University of Valencia, although the background reality shown by these studies does not change much. The appearance of life is not an isolated event that could only occur on a fortunate planet – Earth -. "If we accept a quick and deterministic origin of life, there is no reason to doubt that anywhere else in the universe where physical and chemical conditions similar to those of the primitive Earth were given, an emergency has occurred or is taking place right now. life. Another thing is if some day we can have direct evidence of this, "he says.
Iñaki Ruiz-Trillo, a researcher at the Institute of Evolutionary Biology of Barcelona (CSIC-UPF), points out that this new analysis "momentarily advances the date of fossils of older living organisms, but even being around 3.4 billion years ago, it indicates that once there are suitable conditions, it does not seem to be so difficult that life arrives. " "It does not stop being too different from what surprises us, sometimes, finding life on the ice, in places with salinity or extreme temperature. It is clear that a niche like the Earth, once it had adequate conditions, did not take long to populate. We have not detected the fossils, but it does not mean that they are not ", he points out.