Madrid. An extinction similar to the six great ones documented in Earth’s history, including the current one, occurred 550 million years ago, during the Ediacaran period.
This discovery, which is based on evidence of environmental changes, is documented in a publication in the journal Proceedings of the National Academy of Sciences by researchers at the University of California Riverside (UCR) and Virginia Tech.
Although it is not clear if this represents a true “mass extinction”, the percentage of organisms lost is similar to these other events, including the current one underway.
Researchers believe that environmental changes are to blame for the loss of about 80 percent of all Ediacaran creatures, which were the first complex multicellular life forms on the planet.
“Geological records show that the world’s oceans lost a great deal of oxygen during that time, and the few species that survived had bodies adapted for less-oxygen environments,” Chenyi Tu, a UCR paleoecologist and co-author of the paper, said in a statement. study.
Unlike later events, this first one was more difficult to document because the creatures that perished were soft-bodied and were not well preserved in the fossil record.
“We suspected such an event, but to prove it we had to assemble a massive database of evidence,” said Rachel Surprenant, a UCR paleoecologist and study co-author. The team documented the environment, body size, diet, movement ability, and habits of nearly all known Ediacaran animals.
With this project, the researchers sought to refute the charge that the greatest loss of animal life at the end of the Ediacaran period was more than just extinction. Previously, some believed the event could be explained by incorrect data being collected or by a change in the animals’ behaviour, such as the arrival of predators.
“We can see the spatial distribution of the animals over time, so we know that they didn’t just move to another place or get eaten, they went extinct,” Chenyi said. “We have shown a true decline in the abundance of organisms.”
They also tracked the ratio of the creatures’ surface area to volume, a measurement that suggests declining oxygen levels were the cause of the deaths. “If an organism has a higher ratio, it can get more nutrients, and the bodies of animals that lived in the next era adapted in this way,” said UCR paleoecologist Heather McCandless, a co-author of the study.
Ediacaran creatures would be considered strange by today’s standards. Many of the animals could move, but they were unlike anything now alive. Among them were Obamus coronatus, a disc-shaped creature named for the former president, and Attenborites janeae, a small ovoid resembling a raisin named for English naturalist Sir David Attenborough.
“These animals were the first evolutionary experiment on Earth, but they only lasted about 10 million years. Not long, in evolutionary terms,” Droser said.
Although it is not clear why oxygen levels fell so precipitously at the end of the era, it is clear that environmental change can destabilize and destroy life on Earth at any time. Such changes have fueled all mass extinctions, including the one currently occurring.
“Nothing is immune from extinction. We can see the impact of climate change on ecosystems, and we need to keep the devastating effects in mind as we plan for the future,” said Phillip Boan, a UC Riverside geologist and co-author of the study.
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