The strength required to access the high calorie content of bone marrow may have played a key role in the evolution of the human hand and explain why primates’ hands are not like ours, research based at the School of Anthropology and Conservation has found.<\/p>\n
In an article in\u00a0The Journal of Human Evolution<\/em>, a team lead by Professor\u00a0Tracy Kivell\u00a0<\/a>concludes that although stone tool making has always been considered\u00a0a key influence on the evolution of the human hand, accessing bone marrow generally has not. It is widely accepted that\u00a0the unique dexterity\u00a0of the human hand evolved, at least in part,\u00a0in response to stone tool use\u00a0during our evolutionary history.<\/p>\n Archaeological evidence suggests that early hominins participated in a variety of tool-related activities, such as\u00a0nut-cracking, cutting flesh, smashing bone to access marrow, as well as making stone tools. However, it is\u00a0unlikely that all these behaviours equally influenced\u00a0modern human hand anatomy. To understand the impact these different actions may have had on the evolution of human hands, researchers\u00a0measured the force\u00a0experienced by the hand of 39 individuals during different stone tool behaviours \u2013 nut-cracking, marrow acquisition with a hammerstone, flake production with a hammerstone, and handaxe and stone tool (i.e. a flake) \u2013to see which digits were most important\u00a0for manipulating the tool.<\/p>\n They found that the\u00a0pressures varied across the different behaviours, with nut-cracking generally requiring the lowest pressure while\u00a0making the flake and accessing marrow required the greatest pressures.\u00a0\u00a0Across all of the different behaviours, the thumb, index finger and middle finger were always most important.<\/p>\n Professor Kivell says this suggests that nut-cracking force may not be high enough to elicit changes in the formation of the human hand, which\u00a0may be why other primates are adept nut-crackers without having a human-like hand.In contrast, making stone flakes and\u00a0accessing marrow may have been key influences on our hand anatomy\u00a0due to the high stress they cause on our hands. The researchers concluded that eating marrow, given its\u00a0additional benefit of high calorific value, may have also played a key role in evolution of human dexterity.<\/p>\n The manual pressures of stone tool behaviors and their implications for the evolution of the human hand<\/em><\/a>\u00a0by Erin Marie Williams-Hatala, Kevin G. Hatala, McKenzie Gordon and Margaret Kasper, all Chatham University, Pittsburgh, USA and Dr\u00a0Alastair Key<\/a>\u00a0and Tracy Kivell,<\/p>\n","protected":false},"excerpt":{"rendered":"