Age of Bed I, Olduvai Gorge, Tanganyika.

Introduction of the potassium-argon dating method to paleoanthropology, showing that lava at the base of the site of Olduvai Gorge was about 1.8 million years old, and proving that fossils, Australopithecus (Zinjanthropus) boisei, found in Olduvai Bed 1 dated from this time. With J.F. Evernden and G.H. Curtis.