No one knows whether Homo erectus, the ancestor of both the New York Yankees and Boston Red Sox, threw the split-finger fastball.
But he could have, according to a group of scientists who offer new evidence that the classic overhand throw used by baseball players is an evolutionary adaptation dependent on several changes in anatomy. They first appeared, the researchers say, around 1.8 million years ago, when humans were most likely beginning to hunt big game and needed to throw sharp objects hard and fast.
No other primate throws with anything comparable to human force. Chimpanzees, who are much, much stronger, pound for pound, than human beings, can throw, but the best an adult male can do is about 20 mph. A 12-year-old human pitcher can throw three times that fast.
Clearly, the reason is not muscle strength, said Neil Roach of George Washington University, first author of a report in the journal Nature released Wednesday. Roach and his colleagues analyzed the throwing motion of 20 college athletes who hurled baseballs at a target about 100 feet away, with and without a brace that restricted shoulder motion.
They concluded, first, that muscles alone cannot account for how hard and fast humans throw. The shoulder and arm and the rest of the body involved in the throwing motion must be storing elastic energy, like the long tendon of a kangaroo when it hops.
"You're storing energy in your shoulder," Roach said. The storage occurs in the cocking motion, when a thrower brings hand and ball back, preparing to throw.
"It works just like a slingshot would," Roach said. "You're actually stretching the ligaments."
Several developments in anatomy allowed humans to throw this way, he said, including a waist that allows twisting and a relatively open shoulder, compared with those of other primates like chimpanzees.
Looking at the fossil record, Roach and colleagues put the moment at which these changes came together in one body at about 1.8 million years ago, when Homo erectus first appeared.
"It's possible that Homo erectus could throw as fast as we do," Roach said.
What objects he threw is an open question. The most likely are rocks or some sharp projectile in hunting, Roach said. Homo sapiens, the species that would eventually form both the American and National leagues, did not appear until about 200,000 years ago.
Pitching coaches and experts in sports medicine have long analyzed details of the throwing motion.
What is new in Roach's study, say anatomists, is the idea of the shoulder's functioning like a slingshot, and tying specific anatomical changes to the fossil record.
Susan Larson, an anatomist at Stony Brook University School of Medicine who studies human and primate evolution, said the idea that the cocking motion stores energy was "a very novel interpretation."
"I can't say I can find any fault with the study," she said, referring to the analysis of energy involved in throwing. "But I keep thinking, 'Where are we storing this?' "
Larson did disagree, however, on the throwing ability of Homo erectus.
"That's where Neil and I part ways," she said, referring to Roach. "I don't believe that Homo erectus had the broad shoulders that would have given him the ability" to throw the way humans do.