A ‘lost world’ of early microbes thrived one billion years ago

Scientists have discovered a ‘lost world’ of early microorganisms that once thrived in the world’s oceans. Eukaryotes (the group that includes amoebae, mushrooms, plants and people) were thought by some to have become abundant only around 800 million years ago. That’s when ancient rocks bear the telltale signs of the organisms’ existence in the form of fat-like molecules called sterols. But it turns out that precursor ‘protosterol’ molecules are present in rocks dating back even further, to 1.6 billion years ago. The now-extinct eukaryotes that produced these protosterols lived in watery environments between 800 million and 1.6 billion years ago, but were replaced by modern sterol-producing eukaryotes by the end of that period.