Professor and Chair
PhD, University of Chicago, 1976
Dr. Susman's research focuses on early hominins and understanding behavioral pathways in human evolution. Two important innovations took place in the early hominin career. Six million years ago evidence of bipedalism appears in the fossil record. Later, around 2.5 mya, durable artifacts appear followed shortly by fossil evidence of tool behavior. To understand these key events we exploit the extensive and growing fossil record of early hominin evolution and we investigate the comparative and functional morphology of apes and humans and the ecology and behavior of African apes.
Studies of Plio-Pleistocene hominids reveal that while bipedalism characterized the earliest hominins the early bipeds retained ape-like, arboreal positional behavior for approximately 4 million years following the advent of bipedalism. The next plateau is characterized by the evolution of tool behavior. The direct fossil evidence for human-like precision grasping in found the hand and appears around 2.0 million year ago. Study of the comparative anatomy of ape and human hands, the archeological record and the fossil evidence of hominin reveals that, contrary to earlier suggestions, some robust australopithecines in addition to the earliest members of the genus Homo hands capable of human-like precision grasping. South African robust australopithecines possessed adaptations in the hand similar to those of early Homo in East Africa. It thus appears that hominids of the "robust" lineage as well as early Homo all living at 2.0 m.y. were all characterized by the acquisition of the capacity for tool behavior. The earliest evidence of stone tools (2.5-2.7 mya) in East Africa is coincident with the earliest robust australopithecine fossils and both occur prior to the appearance of early Homo.