541-Million-Year-Old Sea Sponge Confirmed As One of Earth’s First Animals
When you think of ancient earth animals, you probably imagine fish, birds and dinosaurs. But a new study published in the Proceedings of the National Academy of Sciences suggests that the first animal on earth was something unexpected: a maritime sponge of 541 million years.
Thanks to the discovery of “chemical fossils”, scientists now have evidence that sea sponges are one of the oldest animals to have ever existed on earth. More specifically, these organizations belong to a class of marine sponges known as demosponges, a group which is still alive today and whose genetics have helped to identify their archaic ancestors.
“We do not know exactly what these organisms look like at the time, but they would have absolutely lived in the ocean, they would have been with a soft body, and we assume that they did not have a silica skeleton,” said Roger Sumons, professor in the MIT’s land department, atmospheric and planetary of planetary sciences, in a press release.
Learn more: Sponges sneeze to eliminate filters
What is a chemical fossil?
Chemical fossils are biomolecules left by a living organism which are then buried, transformed and kept in the sediments. The chemical fossils found in ancient rocks are what helped scientists discover the existence of these sea sponge ancestors.
The chemical fossils identified by this study are known as Steranes, the geologically stable form of sterols, such as cholesterol. Sea sponges produce two specific types of steranes, 30 carbon and 31 carbon. The researchers were able to find an abundance of steranes of 31 carbon particularly rare in samples of rocks of Oman, Western India and Siberia. This observation led them to believe that what they looked at was proof that the sea sponges were present more than 541 million years ago during the Ediacaran period.
“These special steranes have been there from the start. It took by asking the right questions to look for them and to really understand their meaning and where they came from,” Lubna Shawar, Caltech researcher, in the press release said.
Sea sponges: one of the first animals of the earth
The research team discovered for the first time evidence of these old sea sponges in 2009. At that time, preserved sterols of 30 carbon were found in rocks collected in an outcrop in Oman. As mentioned, 30 carbon sterols are a unique type that modern sea sponges still produce.
After identifying these compounds, scientists were certain that the presence of these sterols pointed out that sea sponges were one of the first examples of multicellular life on earth. However, other scientists have challenged this assertion and thought that 30 carbon sterols could have been left by something else, like other non -lively organisms or geological processes.
But with the new discovery of 31 carbon sterols, the original hypothesis has not become stronger. The researchers suggest that the 31-carbon and its creation are unique to the old and modern sea sponges, and that its presence in the precambrian rocks is organic rather than geological.
“This is a combination of what is in the rock, what is in the towel and what you can do in a chemistry laboratory,” Summons said in the press release. “You have three favorable and mutually agreed line lines, pointing that these sponges being among the first animals on earth.”
Future research plans include the search for 30 and 31 carbon sterols in rocks from other places in the world. With more samples, scientists will be able to learn more about the exact dates when these old sea sponges took shape for the first time.
Learn more: Marine creature the size of a palm called the oldest animal in the world
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