Lucy, Our Famed Ancestor, Was a Poor, Inefficient Runner
Lucy, Our Famed Ancestor, Was a Poor, Inefficient Runner
The famous 3.2 million-year-old relative found in Ethiopia in the 1970s, Lucy, has been the subject of a new study that has shown that our early ancestor could run upright, but not very fast – a mere average of 4.97 meters (16.3 feet) per second. Void of the long Achilles tendon and shorter leg muscle fibers present in modern-day humans, who run an average of 7.9 meters (16.3 feet) per second, Lucy had evolutionary evolved enough to run upright – a landmark development on its own.
- Lucy Stood Just 3.5 feet Tall But Towers Over Our Understanding of Human Origins
- Human Ancestors Were Already Bipeds 7-Million Years Ago
Recreating Lucy: A Digital Marvel
The study, published in Current Biology, utilized digital 3D computer simulations developed in the UK and Netherlands by researchers on the Australopithecus afarensis, who lived between 3.9 and 2.9 million years ago in East Africa. This small, comparatively diminutive hominin, walked upright and was thus the favored pick of the research team trying to understand the evolution of bipedalism in the human lineage.
To recreate one of our most famous ancestral fossil’s body and performance, the researchers inputted ‘maximum running speed, the energetic costs associated with running, and her running endurance’. They added the muscular features of modern apes and the surface area of Lucy’s bones to estimate the ancient hominin’s muscle mass.
Simulating running performance in Au. Afarensis. (A and B) Snapshots of the fastest running gait predicted for Au. afarensis where triceps surae architecture was modeled with (A) human-like and (B) an “extreme” non-human ape (NHA) morphology (Bates, Karl T. et al./Current Biology)
The developed simulator then gauged Lucy’s speed doing a model run, running in comparison versus the digital model of a modern human. For accurately determining energy expenditure, the added human ankles showed that Lucy found it much harder to run than us. Despite the lower stature and diminished top speed, Lucy used up to 1.7 times to 2.9 times more energy than modern humans would at that speed.
Apart from large upper bodies, long arms, and short legs, which were hindrances to long-distance running, but the primary reason was a differently shaped Achilles tendon and triceps surae – calf muscles, reports a press release. Contrastingly, modern humans have a long, springy Achilles tendon, connected calf and ankle muscles to the heel bone, which provides high speed running in modern humans.
"This wider context therefore emphasizes the crucial role of the Achilles tendon and triceps surae architecture in the evolution of hominin running energetics. Key features in the human body plan evolved specifically for improved running performance”, the researchers wrote in the study.
- The Death of Lucy: Has a 3.2 Million-Year-Old Mystery Finally Been Solved?
- Human Ancestor ‘Lucy’ Was Athletic and Walked Fully Upright, Finds New Study
Reconstruction of a male (left) and female (right) A. afarensis at the Natural History Museum, Vienna. Right, Lucy skeleton, Cleveland Natural History Museum. (CC BY-SA 4.0/CC BY-SA 4.0/CC BY SA 2.0)
The Evolution of Bipedalism
Lucy likely could run only through short bursts of energy, rather than long-distance pursuits, probably at a time when climbing and walking were more critical than the ability to run.
Historically, the ability to walk and run on two feet is a hallmark of humane evolution, credited to modern humans and their Homo erectus ancestors, dating back 2 million years. In fact, H. erectus had become an adept runner, compared to earlier Australopithecus afarensis, who were still transitioning.
One of the biggest differences between H. sapiens and Lucy’s ilk was that the former evolved to take long strides, compared to very short strides by the latter – a lumbering gait, in fact.
A Guardian report from earlier this year pointed to Darwin’s seminal work from 1871 - The Descent of Man. Darwin had argued that the three human features – bipedalism, tool-making and large brains – evolved in concert, a development in one stimulating the others to evolve further. Lucy subverted this narrative – her skeleton showed that our ancestors walked on two feet long before the brain got bigger.
The study has been able to effectively display the power of seemingly small anatomical differences, like the length of the Achilles tendon, which has profound effects on mobility and energy efficiency. Moving forward, they aim to build on these finds, and plan to model other aspects of Lucy’s locomotion, including arm swing, torso rotation, fatigue, and even bone strain!
Top image: Left; Australopithecus afarensis model reconstruction at the Natural History Museum, Vienna, Right; Reconstructing locomotor anatomy and running performance in Au. Afarensis. Source: Left; CC BY-SA 4.0, Right; Bates, Karl T. et al./Current Biology
