What was Lucy’s impact on our understanding of bipedality, diet, and encephalization?

Session Date: 
Apr 6, 2024

It is an exciting time in paleoanthropology. The pace of discovery of fossils seems to be increasing every year, leading to an expanding cast of characters on our branch of the primate family tree. New analytic approaches leading to insights into what these fossils tell us about our deep past, and what we know about the biology and behavior of our fossil relatives, is transforming our understanding of how we evolved. Yet despite these innovations, we still depend on Lucy. Her discovery 50 years ago marks the halfway point between the discovery of the first Australopithecus fossil at Taung in South Africa in 1924, and today. Lucy rocked the scientific world being such a complete skeleton as well as the oldest australopith. She, along with the First Family, provide a treasure trove of information about A. afarensis from most anatomical regions, from males, females, the young and the old. To this day, Lucy and company remain the primary reference for what the early members of our branch of the family tree were like, especially as A. afarensis remains the best represented species of early hominin in the fossil record. Bipedal posture and craniodental adaptations for eating tough-to-process foods appeared to be the hallmark of the australopith lineage, and the common explanation has remained that this dietary shift led hominins to stand up and become bipeds to move away from the trees in search of these foods. Today, however, even earlier fossil apes and hominins have shown us that bipedality most likely did not evolve from a chimpanzee-like ancestor standing up from all fours, but a more generalized arboreal upright ape who began moving on the ground, still upright, and eventually losing a grasping big toe and fully committing to terrestrial travel. The discovery of even earlier australopiths has shown us that bipedality was established by 4.2 million years ago, whereas the dietary specialization for eating tough-to-process food emerged more slowly over time, so that effective bipedal travel seems to have facilitated dietary change and specialization rather than the other way around. At least some australopiths even appear to have relying on stone tools to aid in this quest, long before the significant encephalization we see in Homo. We now also know Lucy was not alone, but that her species was part of what appears to have been an adaptive radiation of bipedal apes in the mid-Pliocene trying out what it meant to be an early hominin. All of these new insights were built on the foundation of Lucy’s discovery, and to this day, she remains central to our understanding of how we evolved.