Canadian geologist may have discovered the oldest fossil record of animal life on Earth, according to an article published in the journal Wednesday Nature.
About a billion years ago, an area of the Northwest Territories, now formed by rugged mountains, was a prehistoric marine environment, where the remains of ancient sponges can be preserved in mineral sediments, says l ‘article.
Geologist Elizabeth Turner, who works at Laurentian University in Ontario, discovered these rocks in a remote part of the Territories, accessible only by helicopter, where she has been digging since the 1980s. Thin sections of rock contain three-dimensional structures that look like modern sponge skeletons.
“I think these are indeed ancient sponges – only this type of organism has this kind of organic filament network,” said Joachim Reitner, geobiologist and sponge expert at the German University of Göttingen, who did not participate in the Canadian research.
Dating of adjacent rock layers indicates that the samples are around 890 million years old, which would make them around 350 million years older than the oldest sponge fossils found so far.
“What is most astonishing is the age” of the fossils, said Paco Cardenas, a sponge expert at the Swedish University of Uppsala, who was also not involved in the research. “Uncovering sponge fossils from nearly 900 million years ago will dramatically improve our understanding of early animal evolution. “
Many scientists believe that the earliest groups of animals on Earth included soft sponges or sponge-like creatures devoid of muscles and nerves, but which exhibited other characteristics of simple animals, including cells with differentiated functions and sperm.
To be sure, there is very little scientific consensus or certainty around what may be as old as a billion years ago, so other researchers will likely continue to examine and debate M’s findings.me Turner.
“I think she has a pretty solid record. I think it deserved to be published – it makes the evidence available to other people, ”said David Bottjer, a paleobiologist at the University of Southern California, who was not involved in the research.
Difficulty in fossilizing
Scientists believe that life on Earth appeared around 3.7 billion years ago. The first animals appeared much later, but scientists still don’t agree on when.
So far, the oldest undisputed fossil sponges date back to around 540 million years ago, during the Cambrian Period. But scientists using the “molecular clock” estimate that sponges may have emerged much earlier, around a billion years ago – although no physical evidence to support this thesis has yet been found. ‘now.
“This would be the first time that a sponge fossil has been found before the Cambrian, and not just before, but long before – that’s what is most exciting,” Professor Cardenas said, adding that the research seems to confirm the estimates of the molecular clock method.
Fossil evidence is scarce before the Cambrian, when animals first developed hard skeletons, exoskeletons, and shells, which are more likely to be preserved in the ground.
“These types of fossils belong to more complex animals – obviously there has to be a narrative” of simpler animals, like sponges, emerging first on Earth, said article’s author Elizabeth Turner.
The dating to 890 million years ago is significant, because if the identification of the sponge is confirmed, it would show that the first animals evolved before a time when oxygen in the atmosphere and the ocean has reached a level that scientists once thought essential for animal life. Yet recent research shows that some sponges can survive on very little oxygen.
“Everything on Earth has an ancestor. It has always been predicted that the first evidence of animal life would be small and cryptic, a very subtle clue, ”said Roger Summons, a geobiologist at the Massachusetts Institute of Technology, who was also not involved in the research. .
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