Evolution and why chimps can't throw a baseball (or poop) at 90 mph

What do human evolution and baseball have in common? Pretty much everything, according to a new Harvard study.

While anybody who's ever watched a chimpanzee fling poop at the local zoo can confirm that our primate cousins will sometimes nail an unlucky target, it's also quite obvious that their throwing style will not land them any major league pitching contracts. 

According to a study published recently in Nature, the evolutionary and biological seeds for today's 90-mile-per-hour fastball were sewn roughly 2 million years ago. That's when a variety of evolved anatomical features began to coalesce in early humans, giving them the ability to hurl projectiles overhand at greater and greater speeds.

This ability, according to lead author and evolutionary biologist Neil T. Roach, vastly increased early man's ability to kill large prey -- and defend it from scavengers. At the same time, it allowed our ancestors to become part-time carnivores and set the stage for other critical developments.

"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," Roach said in a press release. "If it were not for our ability to throw, we would not be who we are today."

In a series of experiments involving Harvard baseball players, researchers used a variety of braces and other contraptions that they strapped to the athletes' limbs to isolate key movements in the throwing process. In many cases, the devices were intended to impede the players' ability to throw, essentially turning back the evolutionary clock.

What they found was that optimum throwing ability was associated with low, wide shoulders; a long flexible waist and the ability of the upper arm, or humerus, to rotate during the throw. They also found that the tendons and ligaments in modern humans store energy as they are stretched in the shoulder region -- such as when a pitcher cocks his elbow -- and allows for an explosive release of power.

Our chimp cousins lack most of these anatomical features, leaving them with an underhanded softball-like throwing style that would get them laughed off a little league baseball field. (Some chimps can throw overhand, but the results are even less impressive.)

Roach and colleagues say the combination of throwing features first appeared in Homo erectus and were refined as a result of natural selection.

Skilled throwing abilities were particularly important considering that stone tipped spears date back to just 500,000 years ago, the authors note. For most of early man's hunting history, stones and sharpened sticks were the only weapons available.

While the study sheds light on aspects of human evolution, it may also serve as a warning to young athletes today, who spend large amounts of time perfecting their throwing style.

"To successfully learn to throw and use that ability to hunt, our ancestors would need to throw often, but nothing like the 100 or more high-speed throws that some baseball pitchers throw now in the span of hours," Roach said.

"Athletes are overusing this capability that gave early humans an evolutionary advantage, and they're overusing it to the point that injuries are common."

To watch a video on the study's methods above. Return to Science Now Blog.





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