How Evolution Gave Humans the Ability to Throw a Fastball

As babies, it doesn't take long for us to realize that—as fun as it is to grab on to everything within our reach—it's even more fun to chuck those things as far and as hard as we can. And now, thanks to a new study, we know the reason behind that delightfully destructive pitcher's instinct—and it all started with Homo erectus almost two million years ago.

Neil Roach, lead author of the study and professor at George Washington University, is no stranger to the study of throwing mechanics. Previously, though, his test subjects included retired Hollywood chimpanzees, and he ultimately found that, though these star chimps could toss with some accuracy, they were severely lacking in power. Thanks to their high shoulders, chimps are stuck with throwing 20mph underhand balls at best. So this time, wanting to see why that evolutionary divide might have occurred, Roach and his colleagues used motion capture technology and 20 (human) members of Harvard's baseball team to construct 3D representations of every leg, hip, torso, elbow, and shoulder movement behind a fastball.

Ultimately, Roach discovered that the trick behind our speedy toss is the elastic energy produced in our shoulder rotation—the fastest motion a human body is capable of. As Discover Magazine notes:

Professional pitchers can reach a rotation of 9,000 degrees per second. At that speed, if the arm could rotate a full 360 degrees it would complete 25 rotations in one second.

A fact that may be a fun little bonus for us, but for our ancestors, the ability to throw with force could have meant the difference between life and death. Stronger throws allowed easier hunting, which meant more food and a better chance of survival.

There are three upper body anatomical shifts, in particular, that allow our faster throws, and using fossil records, the researchers were able to determine that we started evolving towards this more advantageous ability around two million years ago. Of course, evidence regarding ancient humans' hunting practices is limited, but with the facts we do have, it seems highly likely that baseball's biggest stars owe it all to good ol' Homo erectus. [Nature via Discover Magazine]

Top image of pre-haircut Tim Lincecum from here.