[Editor’s Note: This article first appeared on our sister site, ExplorersWeb.]
If you’ve ever wondered how humans are such proficient and efficient runners, you might want to get to know “Lucy,” the 3.2-million-year-old fossil giving scientists new insight into the origins of running in modern humans.
More than a half-century ago, a couple hundred pieces of bone were excavated from an archaeological site in Ethiopia belonging to a single individual of the species Australopithecus afarensis, an ancestor to humans. The bones amounted to an incredible 40% of the individual’s skeleton, which reportedly got its nickname when the Beatles song “Lucy in the Sky With Diamonds” played at the archaeologists’ camp the night it was found. The discovery was globally lauded, and Lucy became a household name. Over the decades since, the well-preserved fossil has offered archaeologists unique insights into how one human ancestor lived and moved and perhaps how humans eventually came to be.
Now, Lucy is again helping scientists learn about our early evolution — specifically, how we run. Using the shape of Lucy’s bones and data on the muscular structure in apes, researchers recently created a digital model of its leg muscles. They then used this information to simulate our ancient ancestors running in computer models. This research showed that while Lucy could run, the species may not have been well adapted to do so.
A reconstruction of “Lucy,” a 3.2 million-year-old Australopithecus afarensis, whose skeletal remains have helped us to understand our human ancestors. Photo: Shutterstock
Half as Fast as Usain Bolt
These simulations estimate Lucy’s top running speed at 4.97 meters per second, a little over 11 miles per hour. Nowadays, an average runner can hit about 7.9 meters per second, or 17.5 miles per hour, while Usain Bolt ran 10.44 meters per second — over 23 miles per hour — when he set the 100-meter world record. Lucy would also have used up to 2.9 times more energy to run than we do today. Even after corrections for Lucy’s smaller size, the research indicates this species’ running was much slower and less efficient than that of modern humans.
Prior to this recent research, we knew that four million years ago, Australopithecus afarensis could stand and walk. Scientists had believed that the human ability to walk and run efficiently on two legs began roughly two million years ago with the species Homo erectus. What happened between those two points, until now, has been a mystery. Courtesy of this recent work, we understand that, during that time period, an ancestor of humans could run, though maybe not too well just yet.
The shape of Australopithecus afarensis’s body did not lend itself well to running. Photo: Shutterstock
Three Key Adaptations
Dr. Karl Bates, the study’s lead author, told the publication “New Scientist” that humans are “superb and economical runners over almost any distance,” as a species.
Modern humans have a strong, spring-like Achilles tendon, which connects the muscles in our calf and ankle to our heel bone. The elastic nature of the tendon stores and releases energy when we run, making us faster and saving energy. Our calf muscles also play a big role by pushing us forward.
Though Australopithecus afarensis walked upright on two legs, their bodies differed from ours. Lucy stood just one meter tall and had a much smaller frame than us. The fossil has a larger upper body with longer arms and shorter legs. The digital model of Lucy’s leg muscles suggests it had no Achilles tendon and weaker calf muscles, so it would have had to work harder to move quickly. Running would have been slow and inefficient for the individual.
So why has running improved through the evolutionary history of humans and their ancestors? Our ability to run has been crucial to our success as a species. It allowed our ancestors to hunt effectively and widen our range across the planet. “Running speed [helps determine] an animal’s ability to outrun predators and capture prey,” explained Bates in “New Scientist.”
This study indicates that over the two million years between Australopithecus afarensis and Homo erectus, our ancestors evolved longer legs, robust Achilles tendons, and stronger calf muscles. Together, these three key features helped to make us more capable of running well.
For now, we can speculate that Lucy would not win a footrace with the average modern human. And we can wonder what future work in this area will continue to reveal about the origins of running.
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New research shows that modern humans would win a race against Lucy. Photo: iRunFar/Eszter Horanyi
