It's a big year for throwing. The greatest closer in baseball history, Mariano Rivera of the Yankees, is retiring.
Aroldis Chapman, the overpowering Cincinnati Reds reliever, continues to fire fastballs beyond 100 mph.
And now some scientists say they've figured out when our human ancestors first started throwing with accuracy and firepower, as only people can: Nearly 2 million years ago.
That's what researchers conclude in a study released yesterday by the journal Nature. There's plenty of skepticism about their conclusion. The new paper contends that this throwing ability probably helped the ancient Homo erectus hunt, allowing him to toss weapons -- probably rocks and sharpened wooden spears.
The human throwing ability is unique. Not even a chimp, our closest living relative, can throw nearly as fast as a 12-year-old Little Leaguer, said lead study author Neil Roach of George Washington University.
To find out how humans developed this ability, Roach and co-authors analyzed the throwing motions of 20 collegiate players. Sometimes the players wore braces to mimic the anatomy of ancestors, to see how anatomical changes affected throwing.
The human secret to throwing, the researchers propose, is that when the arm is cocked, it stores energy by stretching tendons, ligaments and muscles crossing the shoulder. It's like pulling back on a slingshot.
Releasing that "elastic energy" makes the arm whip forward to make the throw.
That trick, in turn, was made possible by three anatomical changes in human evolution, and Homo erectus, which appeared about 2 million years ago, is the first to combine those three changes, they said.
But others think the throwing ability must have appeared later.
Susan Larson, an anatomist at Stony Brook University who didn't participate in the study, said the paper is the first to claim that elastic energy storage occurs in arms, rather than legs.
The new analysis offers good evidence that the shoulder is storing elastic energy, she said.
But Larson, an expert on evolution of the human shoulder, said she doesn't think Homo erectus could throw like a modern human. She said its shoulders were too narrow and the orientation of the shoulder joint on the body would make overhand throwing "more or less impossible."