3.46-billion-year-old 'fossils' were not created by life forms
Brasier et al., PNAS (2015)

3.46-billion-year-old 'fossils' were not created by life forms

What are the oldest fossils on Earth? For a long time, a 3.46-billion-year-old rock from Western Australia seemed to hold the record. A 1993 Science paper suggested that the Apex chert contained tiny, wormy structures (pictured) that could have been fossilized cell walls of some of the world’s first cyanobacteria. But now there is more evidence that these structures have nothing to do with life. The elongated filaments were instead created by minerals forming in hydrothermal systems, researchers report online today in a new study in the Proceedings of the National Academy of Sciences. After the minerals were formed, carbon glommed on to the edges, leaving behind an organic signature that looked suspiciously like cell walls. So that means for now the record will have to go to rocks that are 30 million years younger—the 3.43-billion-year-old Strelley Pool formation, also from Western Australia, which contains stronger evidence of microfossils: hollow, bag-shaped bodies arranged in chains or clusters.