Run, Lucy, run! Human ancestors could jog, but they couldn’t run far or fast.

Run, Lucy, run! Human ancestors could jog, but they couldn’t run far or fast.

Written by Gemma Conroy & Nature Magazine

Ancient human relatives ran on two legs just like modern humans, but at a much slower pace, a 3D computer simulation suggests. Australopithecus afarensis – A tiny hominin who lived over 3 million years ago.

Herman Pontzer, an evolutionary anthropologist at Duke University in Durham, North Carolina, said the analysis provides a detailed snapshot of hominid running speed and muscular adaptations that enabled modern humans to run long distances. states. “This is a very thorough approach,” he says. This week, the survey results Current biologHi.

afarensis Because they walk upright on two legs, their fossils are a favorite of researchers trying to figure out how bipedalism evolved in the human lineage. But few studies have investigated hominin running ability, as it requires more than just studying fossilized footprints and bones, said study co-author Karl Bates, an evolutionary biomechanics researcher at the University of Liverpool in the UK. says.

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slow monkey

Bates and his colleagues created a nearly complete 3D digital model of the 3.2-million-year-old “Lucy” skeleton. afarensis A specimen discovered in Ethiopia half a century ago. They used the muscle characteristics of modern apes and the surface area of ​​Lucy’s bones to estimate the muscle mass of ancient humans. The researchers then used a simulator to “run” the Lucy model and compared its performance to that of a digital model of modern humans.

Simulations showed that Lucy was able to run on two legs, despite lacking the Achilles tendon lengthening and muscle fiber shortening that are thought to be effective for modern humans’ endurance running. However, speed was not Lucy’s strong point. Even after researchers modified her with human muscle, she could only reach speeds of about 5 meters per second at best. In contrast, the human model ran at about 8 meters per second. Even when researchers removed body size from their modeling, Lucy still ran slower than modern humans, suggesting that her physical proportions were the main culprit. “Even though she trained all her muscles, she was still slower,” Bates said.

The researchers then assessed whether specific muscles were involved in energy expenditure during running. When they added human-like ankle muscles to Lucy’s model, the energy costs were similar to those of other animals of the same size. But when the team replaced the human ankle muscles with those of an ape, running became even more taxing for Lucy. This suggests that adaptations of the Achilles tendon and surrounding muscles allow modern humans to run for long periods of time.

Bates and his colleagues now plan to investigate whether fatigue and bone deformities are also affecting Lucy’s running.

This article is reprinted with permission. first published December 19, 2024.