The discovery confirms that the three known domains of life branched off in different directions 3 billion years ago. That finding broadens the known geographic reach of archaea during that time period, adding proof the ancient organisms existed both in sedimentary environments and in subsurface hydrothermal settings.

The discovery came during chemical examination of shale samples, loaded with oily lipid remains of archaea found in a deep Canadian gold mine near Timmins, Ontario, about 400 miles north of Toronto.

The discovery was made by University of Illinois-Chicago Associate Professor Fabien Kenig; his former doctoral student, Gregory Ventura; Christopher Reddy of the Woods Hole Oceanographic Institution; Glenn Frysinger of the U.S. Coast Guard Academy; and Professor Juergen Schieber of Indiana University.

The project, supported by an exobiology grant from the National Aeronautics and Space Administration, is reported in the early edition of the Proceedings of the National Academy of Sciences.