How Lucy’s Muscles Provide Insight into Early Human Movement

Editors Note: Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news of amazing discoveries, scientific advances and more.

CNN
–

When the remains of an ancient human ancestor were discovered in Ethiopia in 1974, the find provided unprecedented insight into a species that lived millions of years before humans walked the earth.

A rare fossil, representing 40% of the skeleton belonging to a female Australopithecus afarensis, is Her name is “Lucy” from the song The Beatles “Lucy in the sky with diamonds.”

Now, researchers are using the skeletons to work out how these early human relatives moved 3.2 million years ago. The results of the study were published Tuesday in the journal Royal Society for Open Science.

Lucy is shorter than the average human being, about 3.3 feet (1 meter) tall, has an ape-like face and a brain about one-third the size of a human.

Analysis of Lucy’s fossils over the last 20 years shows that she and other species walked upright. But lead study author Dr. Ashley La Wiseman, a research associate at the University of Cambridge in England, wanted to take it a step further and recreate Lucy’s unscratched component: her muscles.

“A particular aspect of what makes us human is the ability to walk on two legs, but understanding how and why this developed has been debated for a long time,” said Weizmann, Leverhulme Trust Fellow and Isaac Newton Trust Fellow. . at the MacDonald Archaeological Research Institute.

“With recent advances in computer modeling, it is now possible to investigate these questions. Of course, in the fossil record we only see bare bones. But muscles move the body – enabling you to walk, run, jump and even dance. So if we want to understand how it powered our ancestors, we first need to rebuild their soft tissue.”

Studying Australopithecus afarensis fossils can provide insight into the evolution of bipedalism, or upright walking, and when it appeared in early human ancestors. Weismann’s reconstruction of Lucy’s muscles can also be used to determine how Lucy moves in other ways.

Weismann and his colleagues developed and initially used a method called polygonal muscle modeling Reconstruction of the missing soft tissue Of the extinct reptiles called archosaurs who lived 247 million years ago.

Then Wiseman applied the same method to Lucy for the first time to understand the shape and size of her muscles and how she used them to move, evaluating whether they were like an upright chimpanzee-like sway or a human posture.

Wiseman used scans of Lucy’s fossils and data from humans to create 3D models of the legs and pelvic muscles of Australopithecus afarensis. After gathering data from MRI and CT scans of musculoskeletal structures in modern humans, researchers digitally created skeletal muscle models.

Next, I used scans of Lucy’s fossils to determine how her joints moved in life. Wiseman layered the 36 muscles in each leg using “muscle maps” from recent human data, along with “muscle scars,” or the obvious traces of muscle connections detectable in fossils.

Lucy’s skeleton differs from humans in that she has shorter legs and a plate-like pelvis (when viewed from top to bottom).

Weismann’s model shows that while the modern human thigh contains about 50% muscle mass, with the rest associated with fat and bone, Lucy’s thigh contains about 75% muscle. In general, Lucy’s leg muscles were much larger and took up more space than modern humans.

Lucy lived 3.2 million years ago on the African savanna. He had to walk on uneven terrain and explore a mixture of forest and open prairie environments,” said Wiseman.

“More muscle mass usually means more muscle strength, and it wasn’t too surprising to find that Lucy’s muscle reconstruction showed she had more muscle mass than humans, allowing her to move freely between these different environments.”

stand up straight

Paleoanthropologists question Lucy’s position because her skeletal structure is different from that of modern humans.

Humans have a stable stance with perfectly straight legs, but when a chimpanzee stands upright, the legs don’t straighten out. They walk in a crouched position due to flexed hips and knees, which is why most chimpanzees walk on all fours.

3D model showing Lucy’s influence Knee extensor muscles Meaning they could stand up straight like modern humans.

“I was very surprised to find that the knee extension muscles (the muscles that produce and keep your knee straight when you stand upright) are comparable to humans,” says Wiseman. “This means Lucy can get up and walk as efficiently as possible.”

Australopiths like Lucy lived in environments that included open grasslands and dense forests, and had bodies adapted to thrive both on the ground and in trees.

“Lucy probably walked and moved in ways we don’t see in living things today,” Wiseman said.

“If Lucy was bipedal like us and only walked on two legs, she should be able to move in about the same way as possible,” said Wiseman.