2023-06-14 02:13:26
Although paleoanthropologists agree that Lucy was bipedal, they disagree on how she walked.
The first digital reconstruction of the muscles of a hominin (primitive human) has shown that 3.2 million years ago, ‘Lucy’, the fossil of Australopithcus afarensis who revolutionized the study of human evolution, was already walking as upright as we are.
The investigation, led by Ashleigh Wiseman, from the University of Cambridge, has modeled in 3D the muscles of the legs and pelvis of the famous Lucy, discovered by Donald Johanson in Ethiopian in 1974.
Named after the Beatles’ hit (“Lucy in the Sky with Diamonds”), it is one of the most complete skeletons of Australopithecus of which 40% of the bones are preserved.
In life, Lucy was 1.10 meters tall, weighed about 27 kilos, and had a skull comparable to that of a chimpanzee and a brain equivalent to a third of ours. It is believed that when she died she was about 20 years old, since she had just gotten her wisdom teeth.
Australopithecus afarensis was an early human species that lived in eastern Africa more than three million years ago and managed to adapt to the forests and savannah, allowing it to survive for almost a million years.
But their main feature is that they could do something that primates cannot do: walk on two legs
However, while paleoanthropologists agree that Lucy was bipedal, disagree on how he walked, and while some believe that it moved crouched down and that, like chimpanzees -our common ancestor- it could walk on two legs, others believe that it moved in a way more similar to our upright bipedalism.
A consensus on fully upright gait has begun to emerge in the last 20 years, and Wiseman’s work bears this out. Details of his research have been published in the journal Royal Society Open Science.
RECONSTRUCCIN DIGITAL
The study was made possible by the open publication of new data on Lucy, which enabled Wiseman’s team to create a digital model of the muscular structure of the hominin lower body.
To recreate Lucy’s muscles, Wiseman used MRI and CT scans of the muscular and bone structures of a modern woman and man to trace “muscle trajectories” and build a digital musculoskeletal model.
Then, he used the virtual models of Lucy’s skeleton to “rearticulate” the joints, that is, recompose the skeleton and recreate its movements in life, and finally compared them with the muscles of modern humans.
The team recreates 36 muscles in each leg, most of them were much larger in Lucy and bulky than those of modern humans.
For example, the major muscles in Lucy’s calves and thighs were more than twice the size of modern humans, since we have a much higher ratio of fat to muscle.
In fact, the muscles they made up 74% of Lucy’s total thigh mass, compared to only 50% in humans.
Lucy’s knee extensor muscles, and the leverage they would allow, confirm the ability to straighten the knee joints as much as a healthy person can today.
“Now we’re the only animal that can stand upright with straight knees, but Lucy’s muscles suggest she was as skilled at bipedalism as we are, though possibly he felt at home in the trees as well. It is likely that he walked and moved in a way that we don’t see in any living species today,” Wiseman summarizes.
These reconstructions will help to study mobility in human beings, and determine “what drove our evolution” and what capabilities “we have lost”, concludes the researcher.
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