The Human Shoulder And Homo Erectus
July 1, 2013 – Scientists say they're figured out when humans first started to throw so well: almost two million years ago.
The study, released on Wednesday, argues the idea that our arms work like slingshots. When the arm is wound back it stores energy by stretching the tendons, muscles, and ligaments crossing the shoulder until the moment when the arm is whipped forward to throw, releasing that power.
The researchers involved looked at the the throwing motions of 20 university baseball players and sometimes placed braces on their arms to see how they would be able to throw with the limitations of a Homo erectus.
The researchers say that Homo erectus, who first appeared two million years ago, was only able to develop "slingshot shoulders" because of evolutionary changes in their waist, arms, and shoulders. Throwing helped Homo erectus survive, allowing them to throw weapons to catch and kill animals.
This study has its critics, though. Susan Larson, an anatomist at Stony Brook University in New York and an expert on the evolution of the human shoulder, doesn't think Homo erectus was able to throw like modern-day humans because their shoulders were too narrow.
The director of the human origins program at the Smithsonian Institution Rick Potts does not agree at all with the study's proposal, saying that it's farfetched to say that being able to throw gave Homo erectus a hunting advantage because it would be hard to accurately throw a spear to kill a large animal.
Whether or not experts can agree on when, why, and how early humans developed the ability to throw, they can all agree that throwing is something distinctly human. Not even our closest relatives, chimps, can throw any better than a 12-year-old Little League baseball player.