June 26, 2013 — Little leaguers and professional baseball
players alike have our extinct ancestors to thank for their success on the
mound, shows a study by George Washington University researcher Neil Roach,
which is featured on the cover of the June 27 edition of the journal Nature.
Of course, the ability to throw fast and accurately did not
evolve so our ancestors could play ball. Instead, Dr. Roach's study proposes
that this ability first evolved nearly 2 million years ago to aid in hunting.
Humans are unique in their throwing ability, even when compared to our
chimpanzee cousins.
"Chimpanzees are incredibly strong and athletic, yet
adult male chimps can only throw about 20 miles per hour -- one-third the speed
of a 12-year-old little league pitcher," said Dr. Roach, the study's lead
author and a postdoctoral scientist in GW's Center for the Advanced Study of
Hominid Paleobiology in the Columbian College of Arts and Sciences.
Funded by a grant from the National Science Foundation, Dr.
Roach and colleagues from Harvard
University set out to discover how humans
throw so well, and when and why this ability evolved.
Using a 3-D camera system, like those used to make video
games and animated movies, they recorded the throwing motions of collegiate
baseball players, finding that the human shoulder acts much like a slingshot
during a throw, storing and releasing large amounts of energy.
"When humans throw, we first rotate our arms backwards
away from the target. It is during this 'arm-cocking' phase that humans stretch
the tendons and ligaments crossing their shoulder and store elastic
energy," Dr. Roach said. "When this energy is released, it
accelerates the arm forward, generating the fastest motion the human body
produces, resulting in a very fast throw."
Dr. Roach and colleagues also found that certain anatomical
features in the torso, shoulder and arm that evolved in our hominin ancestors
made this energy storage possible. These features that allow humans to throw so
well first appeared in the species Homo erectus approximately 2 million years
ago.
"We think that throwing was probably most important
early on in terms of hunting behavior, enabling our ancestors to effectively
and safely kill big game," Dr. Roach said. "Eating more calorie-rich
meat and fat would have allowed our ancestors to grow larger brains and bodies
and expand into new regions of the world -- all of which helped make us who we
are today."
Dr. Roach's study may also have important modern-day
implications for some athletes. Baseball pitchers, for example, throw much more
frequently than our ancestors probably did.
"At the end of the day, despite the fact that we
evolved to throw, when we overuse this ability it can end up injuring us,"
Dr. Roach said.
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