Monday, January 24, 2011
Human Evolution Linked to Throwing Skills
Based on a news release from Indiana University
Human evolution is undeniably linked to the development of speech, social networks, and the use of tools. New research describes how these complex mental processes mean our survival as a species also may have had a lot to do with our ability to throw objects long distances. The study, appearing online Jan. 14 in the journal Evolution and Human Behavior, makes the argument for the link between speech, throwing things, brain function, and human evolution.
First, we need to understand why throwing things was important to our ancestors. Geoffrey Bingham, professor in Indiana University’s Department of Psychological and Brain Sciences said Homo sapiens have been so successful as a species because of three factors: Social organization and cooperation, language, which helps with the former factor, and the ability to throw long distance. This trio allowed Homo sapiens to “take down all the potential competition,” Bingham said. It brought us through the ice ages because Homo sapiens could hunt the only major food sources available, big game such as mammoths and giant sloths.
But what does throwing have to do with speech? The answer relates to the uniquely developed brain regions that control the development of both skills, in similar ways.
Recent theories and evidence suggest there are built-in biases in auditory perception that make it possible for us to understand human speech. A very specific part of the human brain becomes finely tuned to the way sounds are grouped, first into syllables, then words, and, finally, sentences. Without this ability for auditory development, we would not be able to learn and acquire speech, and language would just sound like gibberish.
“Our work on the size-weight illusion is now suggesting that a similar bias exists in object perception that corresponds to human readiness to acquire throwing skills,” Bingham said.
Known as the size-weight illusion, the perceptual anomaly causes humans to under-estimate the weight of an object. When presented with two objects of identical weight, but differing size, humans tend to perceive the LARGER object as LESS heavy.
This bias could easily be misconstrued as merely an error in judgment; we are “bad” at guessing the weight of an object when we are confused by a variety of sizes.
Bingham’s theory suggests this illusion is more a function of an evolutionary bias, rather than a “bad” judgment. Early humans, in under-estimating the weight of a larger object, may have been doing crucial work in the development of fine-tuned motor skills. The type of motor skills that were essential to throwing things. The type of motor skills necessary for successful hunting, and therefore, vital to survival.
If this theory is correct, the perceived “lightness” of the larger object is a psychological artifact of our early ancestors’ ability to select, for example, the best spear with which to hunt the large game animals that were a crucial food source early in our development as a species. Those ancestors that pushed the upper size limit of which tree branches they used to make their spears, may have been able to throw those spears harder and farther. Without this size-weight illusion, the advanced motor skills in this type of hunting and tool-making decisions may not have been possible. Our ancestors with the “size-weight illusion” bias then became the ancestors to survive, procreate, and pass on their genes linked to this development in the human brain.
The advanced development of the brain regions needed for both throwing, and speech, were not present in Neanderthal brains. Considering that Neanderthals and Homo sapiens existed in overlapping periods, but only one species survived, these skills may have been an important part in humans’ competitive edge and natural selection for survival.
This may also explain our fascination with football as a modern day analog to those same skills that enabled our earliest ancestors to survive; running fast and throwing things far.
Read the full article here.
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