A Cambridge College specialist has carefully reproduced the missing delicate tissue of an early human predecessor, or hominin, interestingly uncovering a capacity to remain as erect as we do today.
Using scans of “Lucy,” Dr. Ashleigh Wiseman has 3D-modeled the leg and pelvic muscles of the hominid Australopithecus afarensis, the well-known fossil example found in Ethiopia during the 1970s.
An early human species known as Australopithecus afarensis lived in East Africa more than three million years ago. It was shorter than we are, had a face similar to that of an ape, had a smaller brain, and could walk on two legs. It was able to live in both trees and the savannah, which helped the species survive for almost a million years.
Lucy, named after the Beatles song “Lucy in the Sky with Diamonds,” is one of the most complete Australopithecus specimens ever found, with 40% of her skeleton recovered.
Wiseman was able to create a digital model of the lower body muscle structure of the Lucy fossil using recently published open-source data. The research was published in the Royal Society Open Science journal.
The study recreated 36 muscles in each leg, the majority of which were significantly larger and took up more space in Lucy’s legs than in modern humans.
A 3D polygonal model, directed by imaging filter information and muscle scarring, recreates the lower appendage muscles of the Australopithecus afarensis fossil AL 288-1, known as ‘Lucy’. Credit: Dr. Ashleigh Wiseman
For example, Lucy’s major muscles in her calves and thighs were more than twice as big as those in modern humans because our fat-to-muscle ratio is much higher. In Lucy’s thigh, muscles made up 74% of the mass, while humans only make up 50%.
Paleoanthropologists agree that Lucy walked on two legs, but they disagree about how she did it. She may have moved in a crouching waddle, similar to how chimpanzees, our common ancestor, walk on two legs, according to some. Some people think that her movement was more like our upright bipedalism.
Wiseman’s research lends further support to the consensus that has begun to emerge in recent research regarding fully erect walking. Lucy’s knee extensor muscles and the influence they would permit affirm a capacity to fix the knee joints however much a solid individual can today.
According to Wiseman, who works at the McDonald Institute for Archaeological Research at Cambridge University, “Lucy’s ability to walk upright can only be known by reconstructing the path and space that a muscle occupies within the body.”
A 3D polygonal model, directed by imaging check information and muscle scarring, remade the lower appendage muscles of the Australopithecus afarensis fossil AL 288-1, known as ‘Lucy’. The muscles in this model have been color-coded. Credit: Dr. Ashleigh Wiseman
“We are presently the only creature that can stand upright with straight knees. Lucy’s muscles indicate that she was equally adept at bipedalism as we are and that she might have also been at home in the trees. According to Wiseman, Lucy probably moved and walked in a way that no other living thing does today.
“About 3 to 4 million years ago, Australopithecus afarensis would have roamed East African grasslands and more dense forests. These muscle reconstructions of Lucy suggest that she would have been able to successfully utilize both habitats.”
Lucy was a young adult who probably weighed around 28 kilograms and stood just over 1 meter tall. Lucy’s cerebrum would have been about 33% the size of our own. Credit: Dr Ashleigh Wiseman.
Wiseman started with some living humans in order to replicate this hominin’s muscles. She was able to map the “muscle paths” and construct a digital musculoskeletal model by utilizing MRI and CT scans of the muscle and bone structures of modern men and women.
After that, Wiseman put Lucy’s skeleton back together by “rearticulating” the joints using existing virtual models. This work recreated the movement of each joint in real life by defining the axis from which they could move and rotate. Credit: Dr Ashleigh Wiseman.
Based on pathways from modern human muscle maps and what little “muscle scarring” was visible (the traces of muscle connection on the fossilized bones), muscles were finally layered on top. Without open access science, this examination could never have been conceivable,” said Wiseman.
Scientists can now gain a better understanding of this ancestor’s walking style by using these reconstructions. According to Wiseman, muscle reconstructions have already been used to measure a T-Rex’s running speeds. We want to show the range of physical movement that drove our evolution, including the abilities we have lost, by applying similar methods to ancient humans.”
More information: Ashleigh Wiseman et al, 3D volumetric muscle reconstruction of the Australopithecus afarensis pelvis and limb, with estimations of limb leverage, Royal Society Open Science (2023). DOI: 10.1098/rsos.230356. royalsocietypublishing.org/doi/10.1098/rsos.230356
