![]() ![]() And the combo created the necessary stiffness that enabled us to eventually run marathons and take jumping pictures for social media.Įxperts say the new study is valuable because it’s the first to quantify the stiffness of the transverse arch. The medial longitudinal arch followed-arriving 1.8 million years ago, to be precise. Just as they suspected, the appearance of the transverse arch-which appeared in other hominins more than 3 million years before modern humans walked the earth -was an important element of bipedalism. So Venkadesan’s team developed a mathematical model to reconstruct the history of the human foot by comparing our current arch with fossils from extinct hominin species. The next step was to understand the role of the transverse arch in the context of human evolution. But in the cadaver feet, the researchers were able to remove the elastic tissue in between the long bones-called metatarsals-in order to directly measure the arch’s impact on foot stiffness. In living humans, it’s too difficult to isolate the role of the transverse arch because it works in sync with other foot parts. So they designed a series of experiments in which they conducted bending tests on the feet of two human cadavers. ![]() “We had to come up with a way to test this idea in real feet,” he says. Venkadesan’s team wanted proof that a similar principle- that also explains why folding pizza makes it less floppy-was at work in our feet. Push a finger on the middle of the bill’s arch, and you’ll notice some resistance or stiffness. This creates an arch, running lengthwise down the bill. Lay the money flat and slightly curl its long edges so the middle bends up-as if forming a tube or highway tunnel. It’s easy to comprehend the relationship between an arch’s curve and foot stiffness if you grab a dollar bill. Photograph by Cory Richards, Nat Geo Image Collection Right: A group of senior Singaporeans gather at the Singapore Botanic Gardens for exercise. “There have been major debates on how the shape of the foot relates to stiffness, but they’ve concentrated on the medial longitudinal arch. “We were surprised by what an effect it had,” says Madhusudhan Venkadesan, the study’s lead author and an assistant professor in mechanical engineering and materials science at Yale University. Together, they account for our uniquely human feet’s stiffness, which allows us to push off without falling over and distinguishes us from other primates that need a more flexible foot to grasp tree branches. This upper arch tag teams with the better known example along the bottom side of the foot called the medial longitudinal arch. Unauthorized use is prohibited.Ĭalled the transverse tarsal arch (that’s the horizontal curve across the top of your foot), this previously underappreciated attribute accounts for more than 40 percent of the stiffness of the modern human foot, according to the team of researchers from the United States, Japan and the United Kingdom. ![]()
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