Runners taking part in the Boston Marathon. (Credit: Marcio Jose Bastos Silva/Shutterstock) This Monday the 123rd annual Boston Marathon will take place, with an expected 30,000 participants and a half million spectators. The top finishers should complete the grueling 26.2-mile course in just over 2 hours by clocking a pace of under five minutes per mile. I know. It’s painful to imagine. Most of us couldn't maintain that speed for one mile — forget 26 of them. But take heart, recreational runners of the world. Your endurance abilities are actually extraordinary, when compared to the rest of the animal kingdom. True, other creatures boast greater strength, agility and raw speed. Homo sapiens are relatively pathetic athletes by all measures. But when it comes to long distance locomotion, we're remarkable. After 15 minutes of sustained running, fit humans can outlast nearly all mammals, especially in hot weather. That's more than a useful tip for betting on a hypothetical Interspecies Marathon (or the actual Man vs. Horse Marathon). Rather, it’s the basis for an important idea in human evolution studies. Let’s call it the “running made us human” hypothesis: According to some scientists, distance running was key to our ancestors’ evolutionary success. They say adaptations for endurance allowed early members of the genus Homo to hunt long before the invention of complex weapons. Regular access to meat spurred brain growth, and ultimately, humanity as we know it.