Strike! Humans started throwing with accuracy about two million years ago, according to a new study by researchers, including an Indian scientist.
Researchers found that a suite of changes to our shoulders and arms allowed early humans to more efficiently hunt by throwing projectiles.
These changes helped our ancestors become part-time carnivores and paving the way for a host of later adaptations, including increases in brain size and migration out of Africa.
The study led by Neil Roach, from George Washington University, found that a suite of physical changes - such as the lowering and widening of the shoulders, an expansion of the waist, and a twisting of the humerus make humans especially good at throwing, Phys.Org reported.
While some of those changes occurred earlier during human evolution, it wasn't until the appearance of Homo erectus, approximately two million years ago, that they all appeared together, according to the study by Roach with Madhusudhan Venkadesan from the Tata Institute of Fundamental Research in Mumbai, Michael Rainbow and Daniel Lieberman from the Harvard University .
The same period is also marked by some of the earliest signs of effective hunting, suggesting that the ability to throw an object very fast and very accurately played a critical role in human's ability to rise to the top of the food chain.
Evolutionary changes in the shoulder show that, as a pitcher cocks their arm back, "what they're doing is stretching the ligaments and tendons that run across their shoulder," Roach said.
"Those tendons and ligaments get loaded up like the elastic bands on a slingshot, and late in the throw they release that energy rapidly and forcefully to rotate the upper arm with extraordinary speed and force," said Roach.
That rotation is the fastest motion the human body can produce.
"The rotation of the humerus can reach up to 9,000 degrees-per-second, which generates an incredible amount of energy, causing you to rapidly extend your elbow, producing a very fast throw," Roach said.
Among the evolutionary changes that proved key to generating a powerful throwing motions, he said, was a twist in the bone of the upper arm and an expanded, mobile waist, which both gave early humans the ability to store up and then release more of this elastic energy.
The study was published in the journal Nature.
