Cornelis ('Kase') Klein is Emeritus Professor in the Department of Earth and Planetary Sciences at the University of New Mexico, Albuquerque. He received his BSc and MSc in Geology from McGill University, Canada, and his PhD from Harvard University, also in geology. He has been a member of the Geology faculty at Harvard University, Indiana University, Bloomington and the University of New Mexico: he has taught courses in mineralogy at all these universities. His published books include the Manual of Mineralogy (19th 21st editions, John Wiley and Sons) and the Manual of Mineral Science (22nd 23rd editions, John Wiley and Sons). He has received two awards for excellence in teaching from the University of New Mexico.

J. William Schopf is Professor of Paleobiology and Director of the IGPP Center for the Study of Evolution and the Origin of Life at the University of California, Los Angeles. He is author of "Cradle of Life: The Discovery of Earth's Earliest Fossils "(1999) and "Missing Fossils: Solution to the Mystery of Photosynthesis "(1998), and has edited several other volumes.