When did early humans begin to throw? New research published to the journal Nature reveals that our throwing ability, which helped early Homo sapiens evolve and migrate across the globe, evolved around two million years ago, BBC News reports.
The ability to throw at high speeds is an ability unique to humans, and anatomy changes found in the extinct species Homo erectus, as well as new archaeological evidence, suggest that hunting intensified around this time in human history.
"Success at hunting allowed our ancestors to become part-time carnivores, eating more calorie-rich meat and fat and dramatically improving the quality of their diet," Neil Roach of George Washington University, who led the study, said to BBC News. "This dietary change led to seismic shifts in our ancestors' biology, allowing them to grow larger bodies, larger brains, and to have more children, and it also did interesting things to our social structure. We start to see the origins of divisions of labor around that time, where some would be hunting, others would be gathering new foods. It probably also allowed us to move to new environments, such as areas that did not have vegetation to support us before we had the ability to hunt."
We can throw faster their our closest living relative - the chimpanzee - an animal that can only reach throwing speeds of 20mph. In comparison, most professional athletes can reach speeds up to 90mph.
To understand how we evolved our high speed throwing ability, scientists first took a closer look at the bio-mechanics of throwing by studying the movements of college baseball players.
Using motion capture cameras, researchers observed that during a throw, the human shoulder acts as slingshot as the arm rotates backwards. The ligaments surrounding the shoulders and tendons then store elastic energy which powers the throw forward. Scientists discovered that when this energy is released, it is the fastest motion the human body produces.
Throwing "probably also allowed us to move to new environments, such as areas that did not have vegetation to support us before we had the ability to hunt," said Roach.
Roach added that this idea is still a working hypothesis, and more research is needed on this subject.
Daniel Lieberman from Harvard University, another member of the research team, told BBC News that the most fascinating finding for him was that half of the power derived in a throw comes from elastic energy stored in the shoulder, as it suggests a specific anatomical adaptation.
"That's not a by-product of evolution for something else, it's clearly an adaptation," he said. "There were shifts in our anatomy that enabled us to throw accurately, so we want to understand better just what those early hunting challenges were."
In comparison to animals like cheetahs, lions and leopards, who have the natural defense of claws, Lieberman explained that humans had no such natural weaponry.
"Human hunting is such an fascinating problem and the fact that these features all appear by the time Homo erectus evolved, suggests that hunting may have been a selective force for the ability for throwing," he said, adding that the next step for scientists would be to discover what exactly early humans were using to hunt, as currently no weapons have been found from this time in the archaeological record.
Susan Larson from Stony Brook University, New York, focused her work on the shoulder anatomies of primates and humans in order to study their evolution.
"We're looking at the same fossils, it's a question about how you interpret the anatomy that you see in those fossils," Larson said to BBC News. Homo erectus was not necessarily such a proficient thrower. I think [Dr Roach and colleagues] are discounting the combination of features of how the shoulder as a whole has to work.
"Their [Homo erectus] shoulder still functioned to give the hand a very wide range of motion in order to manipulate things and make tools, but it wasn't designed the same way as it is in humans. You cannot look at just one thing and say how a complicated piece of anatomy works, especially something like the shoulder. You have to understand how all parts work together to bring about a broad range of motion."
Jill Rhodes of Drew University told BBC News that the new research has a stronger theoretical model, more so than any evidence of throwing behavior in Homo erectus.
"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 behavior, there is no evidence for asymmetry in the humeral torsion angle in Homo erectus," she said.
Click here to see images demonstrating the human throwing ability that allowed our ancestors to hunt millions of years ago.
