If you can scorch a baseball over the mound, you can thank extinct ancestors.

That's not to say that, despite what an evolutionary psychologist might contend, our ability to throw fast and accurately evolved so our ancestors could play ball better and therefore get more dates.

Instead, this ability first evolved nearly 2 million years ago -  humans are unique in our throwing ability -  to aid in hunting. 

The researchers used a 3-D camera system, like those used to make video games and animated movies, to record the throwing motions of collegiate baseball players, finding that the human shoulder acts much like a slingshot during a throw, storing and releasing large amounts of energy.  What is the fastest a baseball pitcher can throw?  See here. Actually, Science 2.0 has more baseball science than any consumer site on the planet.

"Chimpanzees are incredibly strong and athletic, yet adult male chimps can only throw about 20 miles per hour—one-third the speed of a 12-year-old little league pitcher," said George Washington University researcher Neil Roach, the study's lead author and a postdoctoral scientist in the Center for the Advanced Study of Hominid Paleobiology, also affiliated with the Department of Human Evolutionary Biology at Harvard University. "When humans throw, we first rotate our arms backwards away from the target. It is during this 'arm-cocking' phase that humans stretch the tendons and ligaments crossing their shoulder and store elastic energy. When this energy is released, it accelerates the arm forward, generating the fastest motion the human body produces, resulting in a very fast throw."

Credit: Harvard University

They also found that certain anatomical features in the torso, shoulder and arm that evolved in our hominin ancestors made this energy storage possible. These features that allow humans to throw so well first appeared in the species Homo erectus approximately 2 million years ago.

"We think that throwing was probably most important early on in terms of hunting behavior, enabling our ancestors to effectively and safely kill big game," Roach said. "Eating more calorie-rich meat and fat would have allowed our ancestors to grow larger brains and bodies and expand into new regions of the world—all of which helped make us who we are today."

Baseball pitchers throw much more frequently than our ancestors probably did and get more injuries as a result.

"At the end of the day, despite the fact that we evolved to throw, when we overuse this ability it can end up injuring us," Roach said.

The next step is researching what humans were throwing so long ago, especially since stone projectile points don't appear in the archaeological record until much more recently. The likely weapons of choice? Rocks and sharpened wooden spears.

Published in Nature, 498, 483–486 (27 June 2013) doi:10.1038/nature12267, Co-authors Madhusudhan Venkadesan (Tata Institute), Michael J. Rainbow (Harvard) and  Daniel E. Lieberman (Harvard).