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Study suggests fossils dating back 900 million years may be the oldest traces of animal evolution – 07/28/2021 – The Science

Filaments of biological origin preserved in Canadian rocks, dating back nearly 900 million years, may be the oldest traces of animal evolution in Earth’s seas, according to a study in the scientific journal Nature. The network of skeletons would correspond to the “skeletons” of fallow animals (popularly known as sponges), the most primitive invertebrates we know today.

Prior to the work, the earliest evidence of animal evolution came from rocks over 600 million years old. So if the new research is correct, it strengthens the long-run hypothesis evolutionary process “In the shadows” they are difficult to detect, before the first animals acquire more complex and diverse forms.

“Regions preserved in the limestone as a microscopic wormhole network are identical to materials described by other researchers in modern rocks, which include the bodies of the sponges themselves,” he explained. Leaf Study author Elizabeth Turner of Laurentian University in Canada. “It’s a very typical style of sponge, which is not usually made up of bacteria, algae, or fungi.”

Turner studies rocks that come from northwest Canada, in the so-called Stone Knife Formation. 890 million years ago, at the beginning of the phase of Earth’s geological history known as the Neoproterozoic, the area had large coral reefs formed from medium and shallow water microorganisms – possibly photosynthetic bacteria, like today’s plants.

The reefs were several kilometers in diameter and 500 meters thick. According to the reconstruction proposed by the researcher, the sponge, which is only 1 cm long, was growing on the edges of the bacterial structures, in places with less light or with more turbulent water (two factors that do not favor the growth of microbe layers much).

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Everything indicates that sponges since the beginning of modern life consisted only of organic matter, without “skeletons” of limestone or silica, like those of some of their modern relatives. Instead, its skeleton was made up of a resistant protein called spongiin.

When the sponge died and began to fossilize, the sponge webs were preserved in the form of small tubes filled with crystals of the mineral calcite.

If Turner’s interpretation of matter is correct, how do we explain the long period of animal life “in the shadows” before other ancestors of invertebrates and vertebrates appeared, between 600 million and 500 million years ago?

“It is possible that sponges, perhaps because they are more tolerant of lower oxygen concentrations than more complex animals, appeared 890 million years ago, while other groups of animals appeared only after the great event of oxygenation of the atmosphere and seas in modern times. . . Sponges may have survived.” The likely one you described is silent in ‘Nirvana’ of corals without experiencing evolutionary stresses,” she wonders.

Turner further explains that efforts to try to “connect the dots” between the two stages of animal evolution are inherently complex because, among other things, one has to find rocks of the right age, which are relatively rare, and spend a lot of time analyzing the traces under a microscope until finding the fossils. that help answer these questions.

“Unfortunately, there has to be tolerance for ‘slow science’ which is very rare these days,”