Non-dominant hand vital to the evolution of the thumb

New research from biological anthropologists has shown that the use of the non-dominant hand was likely to have played a vital role in the evolution of modern human hand morphology: the production of stone tools requires the thumb on the non-dominant hand to be significantly stronger and more robust than the fingers.

University of Kent. In the largest experiment ever undertaken into the manipulative pressures experienced by the hand during stone tool production, biological anthropologist's 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. Key to this is the substantially 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, a trait first thought to have evolved alongside the earliest stone tool use between 2.6 -- 1.4 million years ago. [...] sciencedaily.com

Link 2: La manipulación con la mano no dominante también ha influído en la evolución del pulgar (B&W2)
Los seres humanos modernos poseemos un pulgar de la mano muy derivado, sustancialmente más fuerte y robusto que los otros dedos. Hipótesis anteriores sobre la evolución de tales rasgos se han centrado en la manipulación de los percutores durante la producción y el uso de herramientas de piedra, sin tener en cuenta los factores relativos a la mano no dominante...