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Researchers Unwind the Evolution of Throwing
Key anatomical changes first appear together 2 million years ago, may have aided early hunting.
June 26, 2013
By Danny Freedman
Modern man may have perfected the fastball, but it was our ancestors nearly 2 million years ago who likely were the first to throw it, according to a new study.
The ability to throw objects with speed and accuracy requires a constellation of anatomical features that evolved over time and first came together around 2 million years ago in the early human species Homo erectus, researchers report this week in the journal Nature. The timing, they write, coincides with archaeological evidence of early hunting activity.
The study is the first to trace the origins of powerful throwing and to propose a link to the dawn of hunting, a development that sparked a seismic shift in human history, said lead researcher Neil Roach, a postdoctoral scientist at GW’s Center for the Advanced Study of Hominid Paleobiology.
“Humans are amazingly good throwers,” Dr. Roach said. By comparison, he said, the strong and athletic chimpanzee—one of mankind’s closest-living relatives—throws about one-third the speed of a 12-year-old boy. The difference, the researchers write, is in evolutionary changes to the shoulder, arm and torso that enable human shoulders to gather and release energy like a slingshot.
To identify the mechanics involved, the research team—which included scientists from Harvard University, where Dr. Roach conducted the research as a doctoral student, and the National Centre for Biological Sciences, in India—analyzed the throwing motions of 20 males, most of whom were college baseball players. Using a 3D motion capture system, like those used to make video games and animated movies, the researchers recorded movements as participants threw baseballs at a target, then again while wearing a brace designed to limit their motion to mimic that of human ancestors.
“What we discovered was that during the throwing phase, in which the arm is pulled backwards, humans are storing elastic energy by stretching the ligaments, tendons and muscles that are crossing the shoulder,” Dr. Roach said. Releasing that energy whips the arm forward, generating a high-velocity throw.
“This stored energy allows humans to really ramp up our throwing performance,” Dr. Roach said. It also helps generate the fastest motion the human body produces: the rotation of the humerus, or upper arm bone, which can reach speeds exceeding 9,000 degrees per second, according to the study.
Although some of the upper body features needed for powerful throwing are found piecemeal in even earlier ancestors, they first appear together 2 million years ago in Homo erectus, the researchers write.
Archaeological evidence from around the same time, such as simple stone tools and butchered bones, suggest that early humans were beginning to hunt intensively, Dr. Roach said, and throwing would have been vital to their ability to do that safely.
“Hunting really changed who we are and the way that we, as organisms, interact with the world,” he said. “The additional calories that meat and fat provided would have also allowed Homo erectus to grow larger bodies, bigger brains and to have more babies—all of which helped make us who we are today.”
Becoming “part-time carnivores,” he said, also would have been crucial for allowing Homo erectus to venture out of Africa.
But exactly what these ancestors were throwing 2 million years ago remains an open question, and an area where the team is turning their attention next.
Pointed stone projectiles only date to around half a million years ago, Dr. Roach said, and before then the only weapons available would have been rocks and sharpened wooden spears. The team now plans to study how effective these early projectiles would have been for hunting.