Geoscience Professor John Valley, left, and research scientist Kouki Kitajima collaborate in the Wisconsin Secondary Ion Mass Spectrometer Lab (WiscSIMS) in Weeks Hall at the University of Wisconsin-Madison on Dec. 15, 2017. Researchers J. William Schopf, professor of paleobiology at UCLA, and John W. Valley, professor of geoscience at UW-Madison, have confirmed that microscopic fossils discovered in a nearly 3.5 billion-year-old piece of rock in Western Australia are the oldest fossils ever found and indeed the earliest direct evidence of life on Earth. (Photo by Jeff Miller / UW-Madison)