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Monday, August 20, 2012

The mystery of Neanderthals’ large right arms solved

Researchers from the Universities of Cambridge, Oxford and Pennsylvania State have answered an anthropological puzzle. Why are the right arms of Neanderthals so much more muscular than their left arms? They obviously used their right arms more heavily than their lefts, but for what tasks? Two leading contenders include thrusting spears and scraping hides.

To compare these two activities, thirteen right-handed able-bodied men were set some spearing and scraping tasks. Pieces of carpet stood in for game animals. The volunteers thrust mock spears into scraps of carpet and scraped fibers from other carpet fragments, all while hooked up to electrodes that measured muscle usage.

Spear thrusting seems like an obvious choose for asymmetrical arm use. Unfortunately for this popular hypothesis, the researchers found that this activity makes greater use of the non-dominant (generally left) arm. So, scratch that off the list. In contrast, some of the motions involved in scraping a hide did significantly favor the right arm.

This actually makes sense if you consider that for every successful spear thrust there follows many hours of hide scraping. Thus, it’s not surprising that hide preparation makes a much greater impact on Neanderthals’ anatomy.

PZ Myers of Pharyngula has an alternate explanation.