One of the enduring mysteries in human evolution is the question of how and when humans evolved our unusually large brains. Another mystery is how and why we started moving around on two legs. This episode of Discovering Us explores both of these questions by exploring the human ability to run over long distances.
One of the enduring mysteries in human evolution is the question of how and when humans evolved our unusually large brains. Another mystery is how and why we started moving around on two legs. This episode of Discovering Us explores both of these questions by exploring the human ability to run over long distances.
Further reading
About The Leakey Foundation
The Leakey Foundation is a nonprofit organization dedicated to funding human origins research and sharing discoveries. The Foundation was established in 1968 to fund work at the forefront of fossil and primate studies and provide opportunities for a global community of scientists. Learn more at leakeyfoundation.org.
Discovering Us: 50 Great Discoveries in Human Origins
In 50 lively and up-to-the-minute essays illustrated with full-color photographs, Discovering Us: 50 Great Discoveries in Human Origins presents stories of the most exciting and groundbreaking surprises revealed by human origins research.
Prepared in consultation with leading experts and written by Evan Hadingham, senior science editor for NOVA, Discovering Us features stunning photographs, some taken at the actual moment that groundbreaking discoveries were made. The book presents a highly accessible account of the latest scientific insights into the ultimate question of humanity’s origins. Discovering Us was published by Signature Books.
Find Discovering Us at your local library, bookstore, or amazon.com.
Show Credits:
Discovering Us was made possible by generous support from Camilla and George Smith, the Ann and Gordon Getty Foundation, and the Joan and Arnold Travis Education Fund.
Meredith Johnson:
One of the enduring mysteries in human evolution is the question of how and when humans evolved our unusually large brains. Another mystery is how and why we started moving around on two legs. Today’s installment of Discovering Us explores both of these questions by looking at the human ability to run over long distances.
Here’s Ashley Judd…
Ashley Judd:
Born and Evolved to Run
It began with a pig on a treadmill.
In 1991, Dennis Bramble, an expert in animal locomotion, was visiting a Harvard lab where Daniel Lieberman (lee-burr-min), then a Ph.D. student, was coaxing a pig to trot. As Bramble watched the experiment, he exclaimed, “You know, that pig can’t hold its head still!”
Lieberman says, “This was my ‘eureka!’ moment. I’d observed pigs on treadmills for hundreds of hours and had never thought about this.”
Bramble had a theory for why a pig’s head bobs around at the trot: unlike proficient runners such as horses, dogs, and humans, pigs lack a springy ligament that connects their skulls to their spine, steadying their heads.
Bramble showed Lieberman where the ligament attaches to the base of a human skull; at that spot, there’s a slight but sharp ridge—a bony signature of our ability to run. That raised a couple of big questions: How far back did that signature go in the fossil record? And just how important was running to the evolution of humans?
The questions were of special interest to Lieberman, an avid jogger since his teens and now a Harvard anthropologist.
He and Bramble developed an influential theory that sees the development of running as a pivotal point in human evolution. Regardless of our personal athletic prowess or lack of it, we all share a unique set of adaptations that makes us highly efficient long-distance runners.
Lieberman notes, “We’re loaded top to bottom with all these features, many of which don’t have any role in walking.”
They range from the long, elastic tendons in our legs and the springy arches in our feet to our big knee joints and hefty gluteus maximus, which is crucial for balancing the body during a run: with each forward stride, it contracts, pulling the torso back and preventing us from falling.
Lieberman argues that humans are, in fact, highly tuned running machines to a degree that puts most other species to shame.
While horses, dogs, antelope, and hyenas all gallop much faster than we, only humans can run marathons. Most African animals cannot run at all in midday heat. But humans, with our unique hairless bodies and abundant sweat glands, can keep up a steady jog for hours.
Long-distance running, argue Bramble and Lieberman, enabled our ancestors to leave the safety of the trees and successfully hunt and scavenge in the open savanna.
Before the invention of projectile technology, one key method to bringing down an antelope was to track and pursue it across the landscape until it collapsed from overheating. A modest human running speed is fast enough to drive an antelope from a sustainable trot into a gallop, and at that pace, it can no longer lose heat by panting.
Lieberman says that even he - a middle-aged Harvard professor has run down jackrabbits and horses over long distances. One way to do that -he says - is to make them gallop. As soon as an animal gallops, it cannot pant.
Requiring skilled tracking and cooperation, this technique of endurance hunting is well-documented among recent hunter-gatherers, notably the Tarahumara (tar-uh-hoo-mar-uh) of northern Mexico and the San of the Kalahari Desert.
Groups of San hunters have been observed pursuing antelope in 100° F temperatures, keeping up a steady pace similar to marathon runners for several hours.
They do not need weapons to bring down prey, since heat exhaustion alone will finish the animals off.
Two million years ago, our defenseless ancestors on the open savanna had no projectile weapons, yet they had to compete for meat with fearsome lions, cheetahs, and hyenas.
Around that time, the appearance of Homo erectus—notably the Turkana boy with his long, lanky, and athletic build—marks the arrival of long-distance running adaptations for the first time in the fossil record, including that telltale bump on the skull that helps steady the head.
It was a vital step along the long road of humanity’s emergence. Only endurance running and persistence hunting, Bramble and Lieberman argue, can explain how our ancestors gained regular access to meat sources that were crucial to fueling the expansion of our big brains.
[MUSIC rises and then ducks under closing credits]
Meredith Johnson:
Discovering Us: 50 Great Discoveries in Human Origins was written for The Leakey Foundation by Evan Hadingham. It was published by Signature Books. The stories are read for you by Ashley Judd.
All the episodes of this audio companion are available to listen to right now! Make sure to subscribe and share this series with a friend.
You can buy a copy of Discovering Us at your local bookstore or wherever you buy books. There’s a link in the shownotes.
The Leakey Foundation is a nonprofit organization dedicated to funding human origins research and sharing discoveries. The science you heard about today was made possible by Leakey Foundation supporters. Visit our website to learn how you can get involved. Go to leakeyfoundation.org. That’s l-e-a-k-e-y foundation dot org.
This project was made possible by generous support from Camilla and George Smith, the Joan and Arnold Travis Education Fund, and the Ann and Gordon Getty Foundation.