They are only a centimeter in length, but they may be the remnants of the oldest known animal life on earth. Fossil structures, such as sponges, have been found in the northwest Canada. They lived in the oceans 890 million years ago, according to a study released Wednesday. This discovery challenges the long-held theory that animals appeared only after injecting large amounts of oxygen into the atmosphere and oceans.
Sponges are simple animals With the old story. Genetic analysis of modern sponges indicates their origin between one billion and 500 million years ago. But no sponge fossil has been found so far from this period known as the Neoproterozoic Era.
A record 350 million years old
Elizabeth Turner, a professor at Laurentian University in Canada, explored such fossils in rocks 890 million years old, “made” by bacteria that deposited calcium carbonate. The researcher identified small tube structures there in which the rocks contain contemporary calcite crystals, which closely resemble the skeleton found in modern sponges.
If this discovery, then published in the journal Natural, Confirmed, these fossils are over 350 million years old. “The oldest animals that have appeared in an evolution are sponges. It is not surprising to think that sponges in the tree of animals are simple animals,” he explained.
“Very small and sensible”
If the fossils she saw were actually sponges, the latter measured one centimeter. They were “small and obscure, they lived in dark folds and holes under the outer surface of the rocks,” he explains. They would have lived about 90 million years before the Earth’s oxygen level reached the level believed to be essential for the origin of animals. So before the neoproterozoic antioxidant event.
“If my interpretation of the discovered ‘substance’ were correct, the first animals would have appeared before this event and would have tolerated lower oxygen levels compared to current conditions,” said Professor Turner. “Like some current sponges, the first animals may tolerate low levels of antioxidants,” he thinks. But the most complex animal species appear only after the occurrence of neoproterozoic antioxidants.
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