How throwing evolved into humanity's greatest weaponS

Most human athletic abilities have some equivalent in the animal kingdom. For example, the fastest humans can reach top speeds that aren’t even half those of cheetahs, antelopes, and countless other animals, and that’s hardly the only area where animals can crush our greatest athletes. But there’s one major exception: throwing.

Most species lack the basic anatomy needed to throw a ball, spear, or other projectile, but that still leaves our primate cousins. Our closest living evolutionary relative, the chimpanzee, can throw no faster than 20 miles per hour, which is only a fifth of the top speeds reached by some athletes, most notably pitchers in baseball. It was athletes such as those that researchers studied, as they found that college baseball players used their shoulders like slingshots, storing elastic energy in the surrounding ligaments and tendons before releasing the ball. That ability to store energy in the shoulder is what makes humans’ supercharged throwing abilities possible.

George Washington University researcher Neil Roach, who led the study, says that this evolution dates back to early hominin species like Homo erectus, and this adaptation would have made more complex, throwing-dependent hunting techniques possible. He explains the results of this ancient adaptation to BBC News:

“Success at hunting allowed our ancestors to become part-time carnivores, eating more calorie-rich meat and fat and dramatically improving the quality of their diet. This dietary change led to seismic shifts in our ancestors' biology, allowing them to grow larger bodies, larger brains, and to have more children, and it also did interesting things to our social structure. We start to see the origins of divisions of labor around that time, where some would be hunting, others would be gathering new foods. It probably also allowed us to move to new environments, such as areas that did not have vegetation to support us before we had the ability to hunt.”

Harvard’s Daniel Lieberman adds:

“That's not a by-product of evolution for something else, it's clearly an adaptation. There were shifts in our anatomy that enabled us to throw accurately, so we want to understand better just what those early hunting challenges were. Human hunting is such an fascinating problem and the fact that these features all appear by the time Homo erectus evolved, suggests that hunting may have been a selective force for the ability for throwing.”

For more on this story, check out BBC News. The original paper is available in Nature.

Image of Georgia Tech pitcher DeAndre Smelter by Will Folsom on Flickr.