Sponge Like Fossils Could Be Oldest Animal Ever Found, or Just Squiggles
A sponge-like structure discovered in exposed 890 million-year-old rock in Canada’s Northwest Territories may be the oldest known fossilized animal body, a study whose findings are likely to add another controversy to the debate long standing on the first animal life on the planet.
In an article published Wednesday in the journal Nature, Elizabeth Turner, a geologist at Laurentian University in Ontario, described the branching tubular structures she observed when examining ultra-thin slices – about as thick as a human hair – of what were once reefs in a prehistoric site. ocean. Dr Turner suggests that the mesh-like structures closely resemble the fiber networks of modern keratosis sponges, also known as horny sponges, which are found around the world today.
But she concedes that what she saw under a microscope may not clarify when animal life first appeared on Earth.
“There may be another explanation. My interpretation is not the last word, ”said Dr Turner. “It is possible that I am wrong.
Some believe it is. “It could just be microbial movements,” said Jonathan Antcliffe, an evolutionary biologist specializing in sponges at the University of Lausanne in Switzerland. The evidence supporting the claim that it is the remains of an ancient sponge, he said, “is very, very thin.”
The putative fossils were extracted from the 890-million-year-old Little Dal Reefs in northwestern Canada, which are now exposed parts of the Mackenzie Mountains. If verified, they would predate the oldest undisputed sponge fossil by around 350 million years – a longer period of time than today and when dinosaurs first evolved.
“We’re talking about inserting hundreds of millions of years without leaving a trace” of fossils, said Graham Budd, a paleobiologist at Uppsala University in Sweden who was not involved in the article. “It would be sensational. It would be like finding a computer chip in a 14th century monastery.
The research highlights the challenges of identifying and making sense of the earliest available fossil records when scientists can’t know exactly what to look for and when there isn’t much to look at. “If we expect the first animals to be tiny and soft,” said Maja Adamska, an evolutionary biologist at Australian National University who was not involved in the new article, “it’s best. which we can expect “.
There have been other controversial claims regarding the timeline of the emergence of life on Earth. Finds of ancient “spongy” fossils have been reported – and later disputed – in Namibia, Russia, Australia, China, Newfoundland and Ukraine. In the early 1990s, scientists at the University of California, Los Angeles claimed to have found the oldest fossils forged by bacteria in the world, which were then discarded as oddly shaped minerals. In 2016, scientists suggested that 3.7 billion-year-old conical structures discovered in Greenland extended the fossil record by 200 million years; two years later, a three-dimensional analysis refuted the fossil claims.
“The further back in time you go, the more difficult it becomes to interpret,” said Gert Wörheide, paleontologist and geobiologist at the Ludwig Maximilians University in Munich. “It’s speculation, and that’s good.”
In the study of the evolution of sponges, horny sponges are notoriously difficult. They lack many of the animal’s most distinct and fossil-friendly features, including mineralized skeletons and skeleton-like spike structures. As a result, there is no scientific consensus on how to distinguish their potential earliest fossils from geological traces of ancient organisms such as fungi or bacteria – or anything else that has since become extinct.
“It is no coincidence that this claim concerns an incredibly misunderstood group,” said Dr Antcliffe. “It’s an inkblot test. They found something and said, “It kind of reminds me of a sponge. “
In the article, Dr Turner argues that the wavy microstructures of reefs are too cohesive and complex to be geological, and do not closely resemble the branching styles of other organisms like fungi or algae.
She adds that the evolution of a life form doesn’t necessarily start with its fossil record (which, for sponges, dates back to 535 million years).
“They did not see the light of day. There must be a history of their evolution, potentially a long evolution, ”said Dr Turner. “We didn’t look enough, part of the reason for the discrepancy.”
On Tuesday, Dr Turner said she was prepared for the document to be criticized, given the field is so full of uncertainties. “I know it’s going to be a binge eating,” she said. “And that’s OK. Bring it on.”
If his hypothesis holds true, the 890-million-year-old sponge fossils raise other difficult questions: How did sponges survive ice ages and dramatic increases in oxygen? How have they managed to escape fossilization or escape the human gaze so far? And when did animal life really start to evolve on Earth?
“We’re really good, way over the edge of what we can be sure of. This article shows you how little we know about it, ”said Dr Adamska. To get conclusive answers, she said: “We need a time machine.”
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