Oldest Eukaryotes Found in 1.7-Billion-Year Ocean Cores Point to Oxygen-Driven Life
Fossils from 1.75–1.4 billion-year-old mudstone cores in Darwin, Australia, include more than 12,000 microscopic remains of the oldest known eukaryotes. Analysis shows these early complex cells lived in oxygenated bottom waters, suggesting oxygen was functionally necessary for their evolution. The fossils mostly occur in oxic, benthic settings, with fewer in anoxic layers, implying a seafloor lifestyle and a delayed transition to open-water, planktonic life during the Neoproterozoic.