MIT researchers identify chemical fossils called steranes in rocks over 541 million years old, suggesting early animals were ancestors of modern sea sponges.

Building on the 2009 finding of C30 steranes in Oman, the team detects C31 steranes and confirms a biological origin, reinforcing the sponge link.

This broader context includes debates about nonbiological origins and shows the findings strengthen the hypothesis that early animals were sponge ancestors.

The researchers present three lines of evidence—rock chemistry, modern sponge chemistry, and laboratory synthesis—to authenticate the biomarker as life-derived.

Direct biological corroboration comes from modern demosponges that produce C31 sterols, illustrating a plausible connection to ancient sponges.

Future work will expand sampling to other regions to refine the timeline of early animal emergence, supported by funding from MIT Crosby Fund, Simons Foundation, and NASA Exobiology.

Laboratory synthesis of eight C31 sterols and simulated long-term geological transformation yielded only two matches to C31 steranes, strengthening the case for a biological origin.

Steranes are remnants of sterols in cell membranes, linking them to demosponges, a major sponge group.

The study supports the idea that sponge ancestors were among the first animals, predating the Cambrian explosion and likely lacking silica skeletons.

Analyses of Ediacaran rocks from Oman, western India, and Siberia identified both C30 and C31 steranes as sponge-derived biomarkers.