WEDNESDAY, June 26, 2013 (HealthDay News) -- Humans may not run faster than a cheetah or swim better than a shark, but they out-throw other species, experts say. And the reasons for that may lie far back in evolution.
People's ability to throw balls and other objects fast and accurately is a trait that developed nearly 2 million years ago to help our now-extinct ancestors hunt with rocks and sharpened wooden spears, new research suggests.
"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," study lead author Neil Roach, of George Washington University, said in a university news release. "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."
Superior throwing skills are unique to humans, the researchers noted, and even our chimpanzee cousins can't come close to matching us.
"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," Roach said.
He and his colleagues used a 3-D camera system to record the throwing motions of collegiate baseball players. They found that the shoulder acts much like a slingshot during a throw, storing and releasing large amounts of energy.
"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," Roach explained. "When this energy is released, it accelerates the arm forward, generating the fastest motion the human body produces, resulting in a very fast throw."
The researchers also found that certain structural features in the torso, shoulder and arm make this energy storage possible.
The findings, to be published July 27 in the journalNature, may have important implications for athletes. For example, baseball pitchers throw much more often than our ancient ancestors did.
"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," said Roach, a postdoctoral scientist in the university's Center for the Advanced Study of Hominid Paleobiology.
The American Academy of Orthopaedic Surgeons discusses throwing-related elbow injuries in children.