Science & Technology, UK (Commonwealth Union) – A scientist from Cambridge University has made a digital reconstruction of the missing soft tissue of an early human ancestor known as hominin, for the 1st time, demonstrating the capability of standing straight as we do today.
Using scans of the renowned fossil specimen ‘Lucy,’ discovered in Ethiopia in the mid-1970s, Dr. Ashleigh Wiseman has successfully employed 3D modeling to reconstruct the leg and pelvis muscles of Australopithecus afarensis, a hominin species that thrived in East Africa over three million years ago.
Australopithecus afarensis, characterized by its smaller stature, ape-like facial features, and relatively smaller brain, exhibited the remarkable ability to walk upright on two legs. This adaptation allowed the species to thrive in both arboreal and savannah environments, enabling its survival for nearly a million years.
Affectionately named after the Beatles classic ‘Lucy in the Sky with Diamonds,’ this fossil specimen stands out as one of the most complete examples ever unearthed belonging to any Australopithecus species, with 40% of her skeletal remains recovered.
Leveraging recently published open-source data on the Lucy fossil, Wiseman successfully generated a digital model depicting the lower-body muscle structure of this 3.2-million-year-old hominin. The findings of this groundbreaking study have been published in the esteemed journal Royal Society Open Science.
The research took place with the reconstruction of 36 muscles in each leg, showing that most of these muscles were significantly larger in Lucy and occupied more space within her legs compared to those of modern humans.
For instance, the major muscles in Lucy’s calves and thighs exhibited a remarkable size that was more than twice that of modern humans. This stark contrast can be attributed to our higher fat-to-muscle ratio. Notably, muscles accounted for a significant 74% of the total mass in Lucy’s thigh, whereas in humans, this proportion stood at only 50%.
While paleoanthropologists unanimously agree on Lucy’s bipedal nature, there is ongoing debate regarding her specific mode of locomotion. Some argue that she moved in a crouched waddle resembling the walking style of chimpanzees, our shared ancestor when they walk on two legs. Conversely, others contend that her movement was close to our own upright bipedalism.
Over the past two decades, research has witnessed the emergence of a growing consensus favoring fully erect walking, and Dr. Wiseman’s work contributes further weight to this perspective. Through her study, the examination of Lucy’s knee extensor muscles and their associated leverage provides evidence of her ability to straighten her knee joints to a degree comparable to that of a healthy individual in the present day.
Lucy who was a young adult, standing at just above 1 meter tall as well as probably weighing roughly 28kg. The brain of Lucy may have been around a third of the size of us.
In her quest to recreate the muscular structure of Australopithecus afarensis, Dr. Wiseman embarked on a process that commenced with the utilization of living humans. By employing MRI and CT scans of a contemporary woman and man, she meticulously examined the muscle and bone structures, enabling the mapping of intricate “muscle paths” and the development of a comprehensive digital musculoskeletal model.
Subsequently, Wiseman employed existing virtual models of Lucy’s skeleton to reconstruct the joints, essentially reassembling the skeletal structure. This crucial step involved determining the axis of movement and rotation for each joint, effectively replicating the dynamic range of motion during Lucy’s lifetime.
To complete the reconstruction, layers of muscles were added on top, drawing from pathways derived from modern human muscle maps. Additionally, Wiseman utilized any discernible evidence of “muscle scarring,” the faint traces of muscle connections observable on the fossilized bones. Wiseman emphasized the vital role of open-access science in facilitating this research, acknowledging that without it, such advancements would not have been attainable.
