Research has unveiled that the non-dominant hand is likely to have played a vital role in the evolution of modern hand morphology.
In the largest experiment ever undertaken into the manipulative pressures experienced by the hand during stone tool production, biological anthropologists analysed the manipulative forces and frequency of use experienced by the thumb and fingers on the non-dominant hand during a series of stone tool production sequences that replicated early tool forms.
It is well known that one of the main distinctive features between humans and our closest evolutionary relatives, the great apes, is the morphology and manipulative capabilities of their hands. The key to this is the considerably larger, stronger and more robust thumb displayed by humans, with such a thumb allowing humans to forcefully and yet dexterously manipulate objects within the hand, an ability first thought to have evolved alongside the earliest stone tool use between 2.6–1.4 million years ago.
Until now however, the evolutionary pressures thought to have selected for this robust thumb anatomy have focused upon the use and production of stone tools with the dominant hand, with the influence exerted by the non-dominant hand having largely been overlooked, despite its vital role in the securing and repositioning of stone nodules (cores/nodules are the piece of raw material from which stone tools are produced).
In the research, PhD student Alastair Key and his research associate Christopher Dunmore, from the University of Kent’s School of Anthropology and Conservation, showed that the production of stone tools requires the thumb of the non-dominant hand to be considerably stronger and more robust than the fingers.
Their results have been published in the Journal of Human Evolution and demonstrate that the thumb and the non-dominant hand was not only required to exert and resist significantly more force than the fingers when manipulating stone cores, but that it was also recruited significantly more often. Therefore this means that our earliest stone tool production ancestors were likely to have experienced similar recruitment levels, with those individuals displaying a stronger, more robust thumb being more capable stone tool producers and thus having the evolutionary advantage.
Contributing Source: University of Kent
Header Image Source: WikiPedia
