 These fossils have been interpreted as traces of eukaryotes and cyanobacteria, though some scientists argue that these biomarkers must have entered these rocks later and date the fossils to 2.15–1.68 Ga.This later time span agrees with estimates based on molecular clocks which dates the eukaryote last common ancestor at 1866–1679 Ma.If the Pilbara fossils are traces of early eukaryotes, they could represent groups that went extinct before modern groups emerged.