Overview

• An MIT-led team reports C30 and C31 steranes in Ediacaran-age rocks from Oman, western India, and Siberia consistent with demosponge biochemistry.
• The study links the rarer C31 signal to sponge genes, bolstering earlier evidence based on C30 steranes reported in 2009.
• Researchers identified matching C31 sterols in some modern demosponges, aligning living chemistry with ancient rock signatures.
• Laboratory synthesis of eight C31 sterols showed only two yield the fossil forms found in rocks, arguing against nonbiological origins.
• The findings, published in PNAS, prompt targeted searches of additional ancient sediments to refine when the first animal lineages emerged.