[ad_1]
Over two decades ago, Elizabeth Turner embarked on a helicopter journey to the Mackenzie Mountains, a vast range nestled in a remote part of northwestern Canada. The mountains offer a window into the ancient past: they contain the geological remains of an ancient reef system, built by algae.
Turner, now a professor of geology at Laurentian University in Ontario, says she wanted to understand reefs on a microscopic and macroscopic level. “They are as big as modern reefs; miles in diameter and hundreds of yards thick,” she notes.
When she first arrived in the mountains, she said she was “stuck” – there was a lot of limestone, a type of rock formed with calcium, but it was mostly featureless. “The weather is just completely gray and you can’t see what’s inside,” she notes. So Turner collected a bunch of samples, from all over the 890 million year old reef (known as Little Dal) and brought them back to the lab to investigate, cutting the rock into incredibly thin slices and l ‘examining under a microscope. .
Among her samples, she spotted something unexpected.
“Just a handful of samples, literally a handful, contained this surprisingly weird and complicated thing that said, ‘I really don’t belong here,'” she recalls. The “strange and complicated thing” was a series of worm-like microstructures. But they had nothing to do with his doctorate. and so she put the find aside. She thought to herself, “I’ll take care of this later.”
Later came much later, as is often the case in academia. These unusual samples didn’t eat into her, but she knew they were important. She says they didn’t appear to be microbial structures – they were too complicated for that. And they had a familiar texture she had seen in younger rocks. Perhaps, she thought, they were associated with sponges: porous, “basic” animals, without organs or nervous systems, who are among the oldest animal residents on Earth.
On Wednesday, in a study published in the journal Nature, Turner sets out his case for this hypothesis, suggesting that the microstructures discovered in the ancient reefs of Little Dal are indeed microfossils of sponges, making them nearly 350 million. years older than the oldest current animal ever described. .
It’s an important claim – and one that will certainly be debated – but Fritz Neuweiler, a geologist at Laval University in Quebec City who was not affiliated with the study, called the work a “good step forward,” noting that the document is “well-founded, courageous and provocative.”
Over 890 million years ago, Earth was a very different place. There was only one supercontinent, known as Rodinia. North America was at the center of this immense land mass, with all the other continents huddled around its edges. The Little Dal Reef System was nestled inland, submerged under shallow ocean waters.
The reef was full of life at the time, mostly occupied by microbes like cyanobacteria or algae, which use the sun for energy just like plants. Stromatolites, mats of bacteria up to three feet high, were also present. Turner says she would have loved to dive into it.
“It would be like this beautiful meadow of stromatolites, it would have been colored blue-green because of the cyanobacteria and it would have been very slimy,” she says.
Elizabeth Turner at work in the field on Baffin Island, Nunavut.
C. Gilbert.
You wouldn’t be able to see these sponges, they were tiny. Today’s sponges come in a wide variety of colors, shapes and sizes, but they are mostly made up of “demosponges,” who are true survivors, living through every major extinction event.
In the days of Little Dal Reef, sponges could not compete for surfaces exposed to the sun, so they likely existed in the spaces in between; between rocks and cracks, between cavities and perhaps also on the sides of the reef.
Living near cyanobacteria, says Turner, would have been very beneficial for the sponges. The cyanobacteria would produce oxygen, which the sponges can use, and “they would probably also have provided a source of food, because the cyanobacteria produce polysaccharides,” she says. Sponges do not have a mouth or organs as such, but allow food to drift in the water, in and out of their body. Living next to algae was like living next to a buffet and an oxygen plant at the same time. Turner calls it “nirvana” for sponges.
As the world changed, the reefs disappeared, but not the potential signs of the sponges. During the life of sponges, they incorporated crystals of the mineral calcite – calcium carbonate – into their skeletons. The reefs were buried over time, but the calcite remained, leaving fossils in the rock for Turner to examine 890 million years ago.
If Turner’s findings are confirmed, they could literally rewrite history.
Turner cites a lot of previous research done by other groups over the past 10 years examining Phanerozoic sponge body fossils. The Phanerozoic Era began around 541 million years ago, just around the Cambrian Explosion, when animals began to appear throughout the fossil record. The most definitive fossil evidence for sponges comes from this time, and a lot of work has been done to explore how signs of creatures can survive to the present day. “In recent years, promising work has been done on how sponges are preserved,” she says.
Turner calls it slow science. She was able to build her hypothesis from clear evidence in the younger sponge literature and thinks her interpretation makes sense. However, she does not put an end to it. “It would be foolish to be overconfident,” says Turner. “I want to recognize that what I’m doing is making an informed suggestion.”
Left: the microstructures found in the rock of the ancient Little Dal Reef.
Right: fragment of the skeleton of a modern keratosis sponge.
CE turner
And the truth is, scientists have come here with sponges and youth before.
Some evidence suggests that sponges may have appeared 800 million years ago, but physical evidence is lacking. A 2016 study claimed to have discovered molecules indicating sponges in a rock that is 650 million years old. Further analysis of these molecules by another group of scientists, including Australian National University geobiologist Jochen Brocks, suggested that these molecules were likely formed by algae and geological forces, and not by sponges.
This means that Brocks is no stranger to overturning claims of “the oldest animal of all time.”
But Brocks doesn’t try to pour cold water on Turner’s ideas, quite the contrary. “I wish these things were sponges because that would be very exciting,” he says. However, he does mention the case of Namapoikia, an organism known from microstructures in limestone that was originally considered known animal life before later evidence shows that it may in fact be formed by bacteria. This case study shows that science works flawlessly, and it’s a good reminder to keep an open mind when it comes to the first animals of all time.
“Especially in carbonate, the most wonderful and beautiful things that are biologically looking can develop just by rearranging and pushing the crystals away,” he notes.
Unfortunately, the Little Dal reef system is quite unique, making it difficult to find similar microstructures from other formations around the world. “There are no other examples of this type of reef at this particular age of the rock,” Turner said. Finding other examples of these microstructures and confirming that they are body fossils of ancient sponges will then take time.
But after two decades of thinking about what those structures might be, Turner has a habit of going slow. It may well be that these structures weren’t formed by sponges at all, but something even more exotic that we haven’t even considered yet.
“We are facing this this depth of time here,” she said. “Maybe there was another type of organism that was doing a three-dimensional anastomosed mesh, right? We don’t really know.
[ad_2]
Source link