Because of its age, the Isua Greenbelt has long been the focus of studies seeking to identify signs of early terrestrial life. In 1996, geologist Steve Mojzsis and colleagues hypothesized that isotopically light carbon in the structure's carbon-rich layers was suggestive of biological activity having occurred there. "Unless some unknown abiotic process exists which is able both to create such isotopically light carbon and then selectively incorporate it into apatite grains, our results provide evidence for the emergence of life on Earth by at least 3,800 Myr before present."