Monday, August 5, 2013

Born to throw: another part of early hunting strategies?

in search of antelope?
I've read and heard how running, as part of a strategy of persistence hunting, was critical to human development on the African savanna.

But until just this week I hadn't heard the same for throwing!

A recent study suggests that hunting was also the impetus behind baseball, javelin, and maybe even football, cricket, and tennis.

We humans (OK, not me, but others) have the unique ability to throw a rock, ball, spear or other object both far and fast, an ability that researchers from George Washington University in the U.S. say evolved nearly 2 million years ago to facilitate hunting.



rocks, spears, and boomerangs
all require fast, accurate throwing
image credit: Aboriginal Dreamtime Stories
It makes sense, as you can imagine the usefulness of hurling spears or rocks quickly and accurately when they were available (or cleverly brought with you) in the presence of a fast-moving kangaroo or antelope.

Since early humans are thought to have been scavengers before mastering hunting, being able to throw stones or other objects would also have enabled them to defend, from a safe distance, either themselves or a carcass against a lion or pack of hyenas.

For early humans, Homo erectus in this case, who could walk upright on two legs and thus were slower than many other mammals but had their arms free, throwing projectiles as a hunting strategy likely played an important role in our evolution.

In fact, changes in the anatomy of our shoulder, arm, and torso that appear in ancient skeletons around 2 million years ago coincides with archaeological evidence that suggests that active hunting intensified around the same time.

Humans have shorter forearms, which allow greater throwing accuracy and a flattened, faster throw trajectory that helps hit a target squarely and quickly, before it can run away.

Scientists leading this study collected motion data from baseball players
to uncover why humans are such good throwers.
image: George Washington University

Our shoulder has developed to function like a slingshot when we throw, rotating the arm and cocking it backwards, which stores elastic energy in the arm. When we release the stored energy, our arm can accelerate forward and throw a baseball over 100mph (160kph).

Even though chimpanzees are far stronger than humans, they can't match the throwing power or accuracy of even a human teenager. They do throw things at targets, but mainly to threaten others, not to hunt. [Why are chimps stronger? This New York Times link gives several answers!]

now THAT's strong (but normally not very accurate)
image: Victoria Roberts, NY Times Science


Individuals of Homo erectus had also evolved larger brains than either chimpanzees or earlier humans, which likely enabled them to produce better weapons, learn and track behavior of other animals when chased, maintain pursuit over time, and remember how to return home.

So play ball! But careful if you are a baseball pitcher - the study's lead author, Neil Roach, acknowledged that even though we evolved to throw, overusing our ability can still injure us. Another plug for cross-training.

Texas Rangers' Yu Darvish pitching
photo: Louis De Luca

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