It's easy to marvel at the athleticism required to throw a 90-mile-per-hour fastball, but when Neil Roach watches baseball, he sees something else at work – evolution.
That ability – to throw an object with great speed and accuracy – is a uniquely human adaptation, one that 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 (June 26) in the journal Nature. The study was led by Roach, who recently received his Ph.D. from Harvard's Graduate School of Arts and Sciences and is now a postdoctoral researcher at George Washington University, with Madhusudhan Venkadesan of NCBS 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. They found that a suite of changes to our 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. "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, were 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, approximately 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 human's ability to rise to the top of the food chain.
"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," Lieberman said. "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."
To start unpacking the evolutionary origins of throwing, Roach began not by studying how humans throw, but how our closest relatives – chimpanzees – do.
Though they're known to throw objects (often feces) underhand, chimps, on rare occasions, do throw overhand, but those throws are far less accurate and powerful than those of the average Little League pitcher, Roach said. Additionally, chimps throw as a part of display behavior and never when hunting.
Written By: PhysOrgcontinue to source article at phys.org