London, Sep 11 (IANS): Research shows that the non-dominant hand is likely to have played a vital role in the evolution of the modern human hand morphology.

Alastair Key and Christopher Dunmore from the University of Kent showed that production of stone tools required the thumb on the non-dominant hand to be significantly stronger and more robust than the fingers.

"The thumb on the non-dominant hand was not only required to exert and resist significantly more force than the fingers when manipulating stone cores but it was also recruited significantly more often," Key explained.

This means that our earliest stone tool producing 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 an evolutionary advantage.

During the study, the team 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 cousins, the great apes, is the morphology and manipulative capabilities of their hands," Dunmore noted.

Key to this is the substantially larger, stronger and more robust thumb displayed by humans. Such a thumb allowed humans to forcefully and yet dexterously manipulate objects within the hand - a trait first thought to have evolved alongside the earliest stone tool use between 2.6-1.4 million years ago.

The findings were reported in the Journal of Human Evolution.