1.7-billion-year-old fossils reveal a crucial clue to the rise of complex life

Stored in an open-air warehouse in tropical Darwin, Australia, are dozens of trays containing cylindrical cores of rock. They are from drill holes bored hundreds of metres below the surface by mineral exploration companies decades ago.

Some of these cores at the Northern Territory Geological Survey are mudstone - a type of sedimentary rock formed from hardened seafloor mud. The companies that drilled these cores were largely unaware that within these mudstones were fossils of microscopic organisms buried on the seafloor of an ancient inland sea that covered much of northern Australia over 1.5 billion years ago.

As our new study , published in Nature , shows, these fossils are crucial for addressing a longstanding puzzle about the major evolutionary leap that led to all complex life on Earth: the origin of eukaryotes.