Professor Klein researches the archeological and fossil evidence for the evolution of human behavior. He has done fieldwork in Spain and especially in South Africa, where he has excavated ancient sites and analyzed the excavated materials since 1969. He has focused on the behavioral changes that allowed anatomically modern Africans to spread to Eurasia about 50,000 years ago, where they swamped or replaced the Neanderthals and other non-modern Eurasians.

After earning his undergraduate degree from the University of Michigan, Professor Klein went to the University of Chicago to pursue his M.A. and Ph.D. degrees. Following receipt of his doctorate, he taught at the University of Wisconsin-Milwaukee, Northwestern University, the University of Washington, and for 20 years at the University of Chicago. He came to Stanford from Chicago in 1993.

Professor Klein has served on numerous editorial and advisory boards, he has edited The Journal of Archaeological Science since 1981, and he co-chairs the Grants Committee of the L.S.B. Leakey Foundation. He is a member of the American Academy of Arts and Sciences and of the National Academy of Sciences.