Researchers plan to survey additional ancient rock regions to refine the timing of the appearance of these early animals during the Ediacaran period.

The study uses multiple lines of evidence—comparisons to modern sponges and controlled laboratory chemistry—to authenticate biomarkers and exclude non-biological sources.

A new study published in the Proceedings of the National Academy of Sciences presents sponge-specific sterane biomarkers, specifically C30 and C31 sterols, as evidence of early sponge life.

MIT researchers identified chemical fossils in rock samples over 541 million years old that they attribute to the ancestors of today’s demosponges.

The investigation is supported by multiple funders, including the MIT Crosby Fund, the Simons Foundation Collaboration on the Origins of Life, and NASA’s Exobiology Program.

Evidence suggests these ancient organisms inhabited the ocean, were soft-bodied, and likely lacked silica skeletons, indicating sponges as among Earth’s earliest animals.

Building on 2009 findings, the team identified C31 steranes and confirmed their biological origin through analyses of modern demosponges, lab synthesis of C31 sterols, and fossilization simulations.

The presence of C31 sterols alongside C30 sterols, and their alignment with sponge biology, strengthens the case that demosponges’ ancestors left a lasting chemical record in Precambrian rocks.

Samples were collected from Oman, western India, and Siberia to search for sterane signatures in Ediacaran-period rocks dating roughly 541 to 635 million years ago.