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Simulations of hominin Lucy help show how long distance running evolved in modern humans

A team of natural scientists, musculoskeletal specialists, and evolutionary biologists affiliated with several institutions in the U.K., working with a colleague from the Netherlands, has found via simulations, that the famous early hominin Lucy, could run upright, but not nearly as quickly as modern humans.

In their posted on the open-access site Current Biology, the group describes the factors they put into building their simulation and what it showed them once completed.

The hominin Lucy, found back in the 1970s, in Ethiopia, has over time become the most famous of all the ancient hominins, both because of the good condition of her skeleton, and because of what she has come to represent—proof that humans have evolved from less sophisticated creatures.

Over time, evidence from more fossils left by others of her kind, from 2.9 to 3.9 million years ago, have led scientists to label her as a member of Australopithecus afarensis—an extinct species of australopithecine. In this new study, the research team wondered if Lucy could run on two legs, and if so, how fast. Evidence of such running, they noted, could perhaps reveal more about the evolutionary process that led to modern humans being such good long and short distance runners.

To determine if Lucy could have run upright, the research team used a simulator that has been developed over time for analyzing locomotion in humans and other animals. They added Lucy's skeleton and then added muscular features found in modern apes to flesh her out—and then set the simulator in motion.

It showed that Lucy could indeed run upright, despite lacking the long Achilles tendon that has evolved in humans and the shorter muscle fibers in her legs. Prior research has shown that such fibers help with endurance running.

The simulation also showed that Lucy could not run nearly as fast as modern humans, likely reaching top speeds of just 5 meters per second, even after they gave her modern human-type muscles. Modern humans can on average, run at top speeds of 8 meters per second. The researchers also found that adjusting for body size did not change running speed very much.

The researchers also tested energy expenditure by giving Lucy human ankle-type muscles—the simulation showed similarities to other animals of her size. But running would clearly have been more taxing for Lucy, suggesting she likely would have only done it when it was really needed. This, the researchers suggest, indicates that the Achilles adaptation along with muscle fiber evolution likely allowed early humans to run farther as they evolved.