Researchers from the University of Tokyo found deposits of carbon isotopes in sedimentary rocks in Canada's northeast, which turned out to be the product of living organisms.
By analyzing isotopes, researchers can identify whether they are biogenic — namely contain early cells of living systems — or are a result of some geochemical process.
A large number of graphite samples allowed the research team to reveal details of how these organisms looked like and in what conditions they lived.
For instance, low concentration of "heavy" carbon in the deposits indicated that the bacteria were feeding on hydrogen.
At the same time, many scientists doubt this idea, pointing out the absence of many critical elements, such as boron or manganese, in the ocean and their availability on the surface.
Further excavations, Japanese researchers hope, will help them get more detailed information about early organisms.