Researchers discuss the evidence at the Dresser Formation
Biomarkers: The way forward
Biomarkers are steranes and hopanes; the stuff left over from life. The more ancient the circumstances for life, the harder it is to detect and place with the putative life. At 2.8 billion years biomarkers can be detected in association with fossils of that age. Older than that become problematic, but organic geochemists are working at pushing back the limits of knowledge. Without biomarkers, context, shape and other lines of evidence are used.