Dr. David Green, Midwestern University – How Australopithecus Lived

Feb 1, 2013

In today’s Academic Minute, Dr. David Green of Midwestern University explains what a recent find reveals about how Australopithecus lived. 

David J. Green is an Assistant Professor of Anatomy in the Chicago College of Osteopathic Medicine and College of Dental Medicine-Illinois at Midwestern University. His research interests include early hominin evolution and locomotion and comparative primate shoulder functional morphology. Dr. Green obtained his Ph.D. in Hominid Paleobiology from The George Washington University and B.A. in Biological Anthropology and Anatomy from Duke University.

About Dr. Green

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Dr. David Green – How Australopithecus Lived

Bipedal locomotion is one of the most important characteristics of the human species – one that distinguishes us from all other primates. Researchers that study early human evolution endeavor to find evidence for upright walking when trying to determine if a particular fossil belongs to our lineage, which split from that of chimpanzees roughly 6 to 7 million years ago. But how rapid was this transition to bipedalism, and once our ancestors began walking upright, did they completely abandon other forms of locomotion, or did they maintain a diverse locomotor repertoire like most primates do today?

My coauthor and I explored these questions in a recently published study that investigated the shoulder blades of a 3 to 4-million-year-old extinct human species, Australopithecus afarensis, a group known to possess bipedal adaptations. Shoulder morphology is a reliable predictor of locomotor behaviors and a new skeleton from Ethiopia, named “Selam”, preserves both complete shoulder blades. These bones rarely fossilize and Selam was only 3-years-old when she died, providing us with the opportunity to investigate Australopithecus locomotion and development.

Selam’s shoulders were more similar to those of gorillas and chimpanzees than to modern humans, which supported our hypothesis that Australopithecus maintained adaptations to climbing, in addition to walking upright. Selam’s shoulders were also similar to other adult australopiths, a trend we see in modern apes, but not humans. This implies that Australopithecus maintained apelike behavioral and developmental patterns and suggests that the transition to dedicated bipedalism was not rapid. We contend that our ancestors were still climbing trees to find food and evade predators roughly 3 million years after first  taking to the ground on two feet.