Lucy loved the land, new research suggests. A study in this week’s edition of the journal Science puts forth a foot bone from the early hominid Australopithecus afarensis (Lucy’s kind) as evidence that this species was built for walking—meaning human ancestors could have been striding around on ground level for most of their lives by 3.2 million years ago.
Scientists already knew that A. afarensis could walk on two feet but were unsure whether the creatures climbed and grasped tree branches as well, much like their own ancestor species and modern nonhuman apes. The fourth metatarsal … shows that A. afarensis moved around more like modern humans. “Now that we know Lucy and her relatives had arches in their feet, this affects much of what we know about them, from where they lived to what they ate and how they avoided predators,” said Carol Ward. [The Guardian]
The bone in question comes from Ethiopia, home to many significant hominid finds. And though it is just a small sample, that arched shape in the foot bone suggests Australopithecus had rigid feet, and may not have been much better at climbing trees than you or I.
Arches were an important part of our evolution into humans, because they make climbing trees much harder. The arches on the inside of the foot, nearer to the big toe, serve as a shock absorber when we plant our feet back on the ground. All other living primates have feet made for grasping and bending to hang onto tree branches and their young, more like our hands than our feet. [LiveScience]
Neanderthals: They weren’t really into distance running. According to research by David Raichlen in the Journal of Human Evolution, they were more the power walking type: The shape of a Homo sapiens heel compared to that of a Neanderthal would have allowed our ancestors to be much more efficient runners over long distances.
Raichlen stated with living humans, studying them as they ran on treadmills.
By looking at MRI scans of their ankles, he found that the distance between a point on the heel bone just below the ankle bone, and the back of the heel bone where the Achilles tendon attaches, was proportional to the runner’s efficiency. The shorter this distance, the greater is the force applied to stretch the tendon – and the more energy is stored in it. This means that people with shorter distances are more efficient runners, using less energy to run for longer. [New Scientist]
With this knowledge, Raichlen and colleagues looked at the remains of Neanderthals as well as humans of the same era. The difference, he says, was distinct.
Perhaps the original design is still the best. In this week’s Nature, Harvard’s Daniel Lieberman and his team reported on the impact force of people who are used to running barefoot versus those of us who wear spongy sneakers to protect the bottoms of our feet. Those who ran barefoot (the way humans evolved to run) moved differently, and with far less stress on their feet than the shoe-wearing masses.
The researchers first traveled to Kenya to watch endurance runners who grew up running sans shoes. The study—the first to test lifelong barefoot runners and not simply people trying it out—found that the barefoot runners landed on the front or middle of their feet. By contrast, runners in shoes typically land on their heels. Lieberman says: “This creates an impact; it’s like someone hitting your heel with a hammer with up to three times your body weight” [BBC News]. In follow-up tests in the United States, the team noted that barefoot runners put, on average, only a third of the initial impact force on their feet than their shod counterparts did.