Newly discovered biomarker signatures point to a whole range of previously unknown organisms that dominated complex life on Earth about a billion years ago. They differed from complex eukaryotic life as we know it, such as animals, plants and algae in their cell structure and likely metabolism, which was adapted to a world that had far less oxygen in the atmosphere than today. Benjamin Nettersheim from the MARUM – Center for Marine Environmental Sciences, University of Bremen and Faculty of Geosciences at the University of Bremen and an international team of researchers now report on this breakthrough for the field of evolutionary geobiology in the journal Nature.