A new study by MIT geochemists has revealed first-of-its-kind evidence of the first animals that appeared on Earth.

The first animals on Earth were likely ancient ancestors of modern sea sponges. The findings, published recently in the Proceedings of the National Academy of Sciences, identify "chemical fossils" in rocks over 541 million years old that point to early demosponge life existing during the Ediacaran Period.

Chemical fossils are remnants of biomolecules from organisms long extinct but preserved in sediment over hundreds of millions of years.

The research team detected special steranes, geologically stable forms of sterols, essential molecules in cell membranes, specifically linked to demosponges, a diverse class of soft-bodied sea sponges alive today. This discovery strongly

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