Lucy is a famous fossilized skeleton of a hominid species known as Australopithecus afarensis, discovered in 1974 in the Afar region of Ethiopia. She is estimated to be about 3.2 million years old and is significant because she provided key insights into human evolution, particularly in understanding bipedalism (walking on two legs). Lucy’s relatively complete skeleton helped scientists better understand the structure and movement of early hominids.
In 1974, on a survey in Hadar in the remote badlands of Ethiopia, U.S. paleoanthropologistDonald Johansonand graduate student Tom Gray found a piece of an elbow jointjutting from the dirt in a gully. It proved to be the first of 47 bones of a single individual – an early human ancestor whom Johanson nicknamed “Lucy.” Her discovery would overturn what scientists thought they knew about the evolution of our own lineage.
Lucy was a member of the speciesAustralopithecus afarensis, an extinct hominin – a group that includes humans and our fossil relatives.Australopithecus afarensislived from 3.8 million years ago to 2.9 million years ago, in the region that is now Ethiopia, Kenya and Tanzania. Dated to 3.2 million years ago, Lucy was the oldest and most complete human ancestor ever found at the time of her discovery.
Two features set humans apart from all other primates: big brains and standing and walking on two legs instead of four. Prior to Lucy’s discovery, scientists thought that our large brains must have evolved first, because all known human fossils at the time already had large brains. But Lucy stood on two feet and had a small brain, not much larger than that of a chimpanzee.
This was immediately clear when scientists reconstructed her skeleton in Cleveland, Ohio. A photographer took a picture of 4-year-old Grace Latimer – who was visiting her father, Bruce Latimer, a member of the research team – standing next to Lucy. The two were roughly the same size, providing a simple illustration of Lucy’s small stature and brain. And Lucy was not a young child: Based on her teeth and bones, scientists estimated thatshe was fully adultwhen she died.
The photo also demonstrated how human Lucy was – especially her posture. Along with the 1978 discovery in Tanzania offossilized footprint trails 3.6 million years old, made by members of her species, Lucy proved unequivocally that standing and walking upright was the first step in becoming human. In fact, large brains did not show up in our lineage untilwell over 1 million years after Lucy lived.
Lucy’s bones show adaptations that allow for upright posture and bipedal locomotion. In particular, her femur, or upper leg bone, is angled; her spine is S-curved; and her pelvis, or hip bone, is short and bowl-shaped.
These features can also be found in modern human skeletons. They allow us, as they enabled Lucy, to stand, walk and run on two legs without falling over – even when balanced on one foot in mid-stride.
In the 50 years since Lucy’s discovery, her impact on scientists’ understanding of human origins has been immeasurable. She hasinspired paleoanthropologiststo survey unexplored areas, pose new hypotheses and develop and use novel techniques and methodologies.
Even as new fossils are discovered, Lucy remains central to modern research on human origins. As ananthropologist and paleoecologist, I know that she isstill the reference pointfor understanding the anatomy of early human ancestors and the evolution of our own bodies. Knowledge of the human fossil record and the evolution of our lineage have exponentially increased, building on the foundation of Lucy’s discovery.
This article is republished fromThe Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by:Denise Su,Arizona State University
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Denise Su does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
