According to the latest study on the matter, Earth’s first animal was a sponge that resided in the seas. What is even more extraordinary is that the sponge seems to date before the explosion that created life on our planet, named the Cambrian explosion.
A team of MIT researchers have conducted a study on the matter and have reached the conclusion that sea sponges are the first animals that appeared on the face of Earth because they evolved 640 million years ago.
Released on February 22 in the journal “Proceedings of the National Academy of Sciences”, the study consisted of analyzing ancient fossils preserved in an exceptional state. The paleontologists conducted their research on molecular fossils, which are molecule prints left by decaying animals.
Starting from the Cambrian explosion theory that explains that organisms made from a single cell have evolved in creatures consisting of multiple cells, the study focused on the fact that this evolution took place during a very short period of time.
MIT postdoc David Gold from the Department of Planetary, Earth and Atmospheric Sciences who is also the study’s lead author has stated that scientists are sure that multi-cellular creatures have appeared before the evolutionary explosion.
Gold and his team took a close look at the 24-ipc, otherwise known as 24-isopropylcholestane, a lipid molecule. The 24-ipc is a modified type of cholesterol, discovered in a rock sample back in 2009. The rock dated from 640 million years ago and was a certain sign of the presence of life long before the Cambrian explosion.
The scientists first found out the 24-ipc producing gene, and then traced the organisms that carry this particular gene. In this way they were able to determine how the gene changed and evolved through time. In the present, the molecule is produced by some algae and sea sponges. After analyzing thirty organisms including algae, sea sponges, plants and fungi, they found sterols related to the gene that produces 24-ipc.
In the end, the study proved the gene that generated the sterols was sterol methyltransferase. This pointed towards the fact that sea sponges originally developed the sterol methyltransferase gene 640 million years ago. The fact was demonstrated after scientists compared multiple genetic trees.
While it might not sound very exciting, Earth’s first animal was a sponge. The discovery gives us a new insight on the origins of life on our planet, even if they are not related to the Cambrian explosion.
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