Scientists have discovered the oldest molecular sign of animal life, but it didn’t come from a pile of prehistoric bones. While the vast majority of the ancient animals we know about come from fossils left over from the Cambrian explosion — the period when animal life rapidly diversified for the first time — new research shows there were bizarre animals living long before then, but they didn’t leave behind bones or bits. As the authors of the new Nature Ecology & Evolution study show, the evidence they left behind was chemical.
In the new paper, an international team of scientists report the discovery of a biomarker left behind by members of the Animalia kingdom between 660 and 635 million years ago, making it the oldest evidence ever discovered. The biomarker, detected in ancient rocks and oils from Oman, Siberia, and India, is a steroid compound named 26-methylstigmastane, which today is only known to be synthesized by a species of modern sponges called demosponges.