That ability — to throw an object with great speed and accuracy — is a uniquely human adaptation, one that Neil Roach believes was crucial in our evolutionary past. How, when, and why humans evolved the ability to throw so well is the subject of a study published today in the journal Nature. Roach, who received his Ph.D. from the Harvard Graduate School of Arts and Sciences in June, led the study, working with Madhusudhan Venkadesan of the National Centre for Biological Sciences at the Tata Institute of Fundamental Research, Michael Rainbow of the Spaulding National Running Center, and Daniel Lieberman, the Edwin M. Lerner II Professor of Biological Sciences at Harvard. The group found that changes to shoulders and arms allowed early humans to more efficiently hunt by throwing projectiles, helping 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.
“When we started this research, there were essentially two questions we asked: One of them was why are humans so uniquely good at throwing, while all other creatures, including our chimpanzee cousins, are not,” said Roach, now a postdoctoral researcher at George Washington University. “The other question was: How do we do it? What is it about our body that enables this behavior, and can we identify those changes in the fossil record?” What they found, Roach said, was 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 — that make humans especially good at throwing. While some of those changes occurred earlier during human evolution, Lieberman said it wasn’t until the appearance of Homo erectus, about 2 million years ago, that they all appeared together.
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 the human ability to rise to the top of the food chain.
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