Subtitles section Play video Print subtitles This guy made history in 2012 for being the first amputee runner to compete in the Olympic Games. It's Oscar Pistorius, who you might also know for murdering his girlfriend, but this is a video about feet, so let's set that aside. Pistorius had to fight for his right to compete in the Olympics by proving to officials that his blade like prosthetic feet didn't give him an extra advantage over athletes running on regular old flesh feet. There are other blade runners fighting the same fight behind him. The German long jumper, Markus Rehm was barred from competing in the Rio Olympics. The college track athlete Hunter Woodhall had to make the case to the NCAA. And Paralympian Blake Leeper is gearing up for the same fight to compete in the 2020 Olympics. And it all makes you wonder why does the foot designed in a lab looks so different from the biological human foot? It might be because the human foot is kind of a design disaster. Podiatry is a $5 billion industry. A majority of Americans will experience significant foot pain at some point in their lives, and as many as 10% of us will experience inflammation in the band of tissue along our arches, otherwise known as plantar fasciitis. Why though? Weren't humans evolved to walk long distances and isn't walking upright on two legs the trait that for separated us from other primates? So why hasn't natural selection, selected a cooler, better, less injury prone foot for us? Some theories posit that we're so plagued by foot problems because we evolved to walk barefoot out in nature over soft, sweet earth, but now we've thrown off the delicate biomechanical balance of our feet by wearing big mushy, cushiony tennis shoes. Meanwhile, our bones take a beating from walking and standing on super hard surfaces like concrete. But other researchers say it goes back way further than that. Jeremy DeSilva is an anthropologist who studies human evolution and argues that foot problems exist way back in the fossil record. Fossils show evidence of osteoarthritis and compression fractures and flat arches, which means foot pain millions of years ago. DeSilva makes a convincing case that the real source of our foot problems is the janky design. As I mentioned earlier, what we're looking at are our paper clips and duct tape. Our primate ancestors spent most of their time in trees. Our feet then were originally meant for climbing and grasping, but 4 million years ago, and possibly earlier, some apes started dabbling in bipedalism. Experts haven't agreed on why hominids developed this trait. Perhaps it was a more efficient way to travel while scavenging for food, Or maybe it was to enable persistence hunting, tracking prey over such long distances that they became overheated and simply laid down from exhaustion, no weapons required. Whatever the reason, bipedalism is the defining trait of humans. Going bipedal involved some painful anatomical tradeoffs, including everything from where the spine attaches to the skull, to the angle of the femurs, and of course, the shape of our feet. Let's talk mechanics. A foot is a propulsive lever. It needs to be stiff enough that we can push off the ground and propel ourselves forward, but it needs to be elastic enough to store the mechanical energy that's generated each time the foot strikes the ground. That's how designers ended up with this blade shape for athletes. The human foot, on the other hand, has 26 bones, 33 joints and over 100 muscles, tendons and ligaments. That's because it was built for grasping. All those joints let it flex. So it's not inherently rigid enough to give us the propulsive power we need. Here's what had to change. Back when we were climbers, our big toe used to be opposable like our thumbs, but to help make the foot more rigid, it became shorter, stiffer and in line with our other toes. And we developed arches to absorb the force of impact each time our foot hits the ground. Our ligaments got thicker to help hold all these small bones firmly in place. Bipedal Locomotion is a notoriously complex mechanical engineering puzzle that scientists have been working on for decades. And in the case of human feet, you could say natural selection is still in the early design phase. DeSilva uses the ostrich as an example of a foot from the natural world that resembles the prosthetic blades that were perfectly designed for running on two feet. But he also points out birds have a big bipedalism head start. Just look at their ancestors. They've been bipedal for 230 million years, while we've only been bipedal for about five million. And a big takeaway from his talk? Natural selection isn't selecting from an endless menu of options. Rather, it's a constant series of small modifications to the original design. So in our case, it's slowly modified, flexible graspy hands into more rigid propulsive levers, which left us kind of vulnerable to some aches and pains. But considering our feet are modified ape pains, they do a pretty good job. And considering we're the most successful primate, nay mammal nay species(?) on the planet, it's a pretty decent compromise. Thanks for watching. If you're super interested in the scars of human evolution, you can see the whole talk on Boston University's YouTube page. If you liked this video, hit the bell icon so that you can get notified each time Cheddar posts a new video. Thanks again! We will see you next time.