Throwing seems such a natural movement. But about two million years ago, long before Sandy Koufax started mowing down opposing hitters or Joe Montana connected with Dwight Clark with a Hail Mary to capture the 1982 Superbowl for the San Francisco 49ers, throwing was impossible. It took an anatomical evolution to get us to the World Series and snowball fights we so love.
According to new research released Wednesday in the journal Nature, the ability to throw objects at high speeds first evolved in the now-extinct Homo erectus species. Researchers believe the evolution enabled these early hunters to kill their prey using projectile tools. The increased hunting ability allowed them to migrate throughout Africa and Asia and to consume a more varied diet.
"The ability to throw was one of a handful of changes that enabled us to become carnivores, which then triggered a host of changes that occurred later in our evolution," study co-author Daniel Lieberman told The Guardian. "If we were not good at throwing and running and a few other things, we would not have been able to evolve our large brains, and all the cognitive abilities such as language that come with it. If it were not for our ability to throw, we would not be who we are today."
While species related to Homo sapiens, such as chimpanzees, are able to lift and throw objects at up to 20 miles per hours, only humans are able to do so with speed and accuracy. It is elastic energy storage in the shoulder that allows professional athletes to reach speeds of 100 miles per hours or more.
To better understand the anatomy of throwing, a team of researchers from Harvard and George Washington Universities used 3D cameras to record the movements of 20 college baseball players, as they hurled baseballs at a target that was 100 feet away. They were recorded throwing both with and without a movement-hindering brace.
The resulting images showed that the shoulder resembles a slingshot as the arm rotates backwards. The surrounding tendons and ligaments stretch, storing elastic energy that then propels the throwing motion.
"It works just like a slingshot would," lead researcher Neil Roach told the New York Times. "You're actually stretching the ligaments... It's possible that Homo erectus could throw as fast as we do."
The next step in understanding early hunting techniques is for archeologists to identify what tools Homo erectus used in hunting. To date, no weapons have been found from this archeological period.
Several researchers, who were not involved in the study, caution against drawing conclusions from this research. According to the Times, Susan Larson, an anatomist at Stony Brook University School of Medicine, who studies human and primate evolution, says Roach might be overestimating the time of the anatomical evolution. She puts it at hundreds of thousands of years ago, but not quite the 1.8 million that Roach's team estimates.
"The humeral torsion -- the angle at which the head of the humerus (top of the arm) is articulating at the shoulder joint -- does not fall within the range of modern throwing athletes and more relevantly, as throwing is a one-handed behaviour, there is no evidence for asymmetry in the humeral torsion angle in Homo erectus," Drew University researcher Jill Rhodes told the BBC.
"This research opens a window into our understanding of past behavior," she said, "but our view is still cloudy."