 In the 1860s there were claims of the discovery of pre-Cambrian fossils, but these would later be shown not to have an organic origin.In the late 19th century Charles Doolittle Walcott would discover stromatolites and other fossil evidence of pre-Cambrian life, but at the time the organic origin of those fossils was also disputed.This would start to change in the 1950s with the discovery of more stromatolites along with microfossils of the bacteria that built them, and the publication of a series of papers by the Soviet scientist Boris Vasil'evich Timofeev announcing the discovery of microscopic fossil spores in pre-Cambrian sediments.