Each year, a small town in Wales holds the Man Versus Horse Marathon. It's a 22-mile race between riders on horseback and runners. And, while horses often win, humans will sometimes prevail.
So what makes humans such endurance running superstars?
The secret weapon is our sweat. We have 2-4 million sweat glands all over our body, which means we can run and cool ourselves at the same time. Having no fur is also a huge plus.
In contrast, dogs rely on panting to cool down, and other animals, like horses and camels, also sweat, but less effectively. As a result, they overheat faster and must slow down sooner.
The mechanics of our running stride also makes us particularly well-suited for endurance running. A human's running gait has two main phases: Aerial when both feet are off the ground and Stance when at least one foot touches the ground.
While in the air, gravity pulls us down, which generates a lot of kinetic energy. However, the second we hit the ground, we instantly decelerate, losing that kinetic energy in the process.
Here's where our special adaptations come in. The tendons and muscles in our legs are very springy. They act like a pogo stick, converting kinetic energy from the aerial phase into elastic potential energy, which we can use later.
In fact, our IT band can store 15-20 times more elastic energy than a chimpanzee's similar body part, the fascia lata. When it comes time to step off, those springy tendons can turn 50% of that elastic pogo-stick energy back into kinetic, making it easier to propel forward. Without that extra energy, we'd have to exert that much more effort just to take a step.
So, why did humans get to be such great endurance runners, anyway?
Some anthropologists believe this became important around 2-3 million years ago, when we started hunting and scavenging. Because we couldn't chase down a gazelle like a cheetah, early humans learned persistence hunting. Where they would track prey over long distances until the prey either overheated or was driven into a trap.
In fact, persistence hunting remained in use until 2014, such as with the San people of the Kalahari Desert.
But distance running can still help you, even if you're not interested in running down your next meal.
Studies show running can lower body weight, body fat, and cholesterol levels. And the longer you train, the greater the health benefits. Just one year of training has been shown to reduce body weight by about 7 lbs, lower body fat by 2.7% and decrease resting heart rate by 2.7%.