The research group made a 3D digital model of “Lucy’s” skeleton. Lucy is an almost complete specimen of Australopithecus afarensis, which was discovered in Ethiopia about 50 years ago, about 3.2 million years old. The researchers used the muscle characteristics of modern apes and measurements of the surface of Lucy’s bones to estimate the muscle mass of this species. Then, with the help of a computer simulator, they moved the digital model of Lucy and compared its performance with the digital model of the modern human.
read more
The simulation results showed that Lucy was able to run on two legs even though she lacked a longer Achilles tendon and shorter muscle fibers. Longer Achilles tendon and shorter muscle fiber seems to be effective in endurance running of modern humans. But speed was not Lucy’s strong point; He walked slowly.
Even when researchers recreated Lucy’s muscles to resemble modern humans, her speed did not exceed five meters per second. In comparison, the modern human model runs at a speed of about eight meters per second. Even when the effect of body size was removed from the model, Lucy was still slower than modern humans. This finding shows that Lucy’s body proportions were the main cause of this limitation. “Even if you strengthened all its muscles, it was still slower than modern humans,” Bates explains.
In the next step, the researchers investigated the effect of different muscles on energy consumption during running. When modern human-like ankle muscles were added to Lucy’s model, her energy expenditure also changed, as did animals of similar size. But when her muscles were replaced with those of monkeys, running became more difficult and more energy-intensive for Lucy. This finding shows that the changes in the Achilles tendon and the muscles around it played an important role in the ability of modern humans to run for a long time.
Next, the researchers plan to investigate how factors such as fatigue and stress on the bones affected Lucy’s ability to run.
