New study suggests human right-handedness originates from tool use
New study suggests that a predominance to be right-handed is not a uniquely human trait
A new study, published in Behavioural Brain Research, suggests that a predominance to be right-handed is not a uniquely human trait, but one shared by great apes. Previously, researchers linked right-handed motor actions to the fact that language skills are driven by the left hemisphere of the brain and pursued the idea that human handedness may be connected with the evolutionary origins of human language. Researchers on the study suggest a new theory; that handedness is a property related to tool use, which is inherited from an ancestor common to both humans and great apes.
Professor Michael Thomas and Professor Denis Mareschal, from Birkbeck’s Centre for Brain and Cognitive Development, were part of a team that studied hand actions of children in naturalistic settings. The technique involved video sampling and coding of activities in four-year-old children within their everyday environments. The simple and non-invasive methodology revealed aspects of brain function and organization without the need for a laboratory setting with expensive and invasive equipment or testing. Each observed hand action was coded as being directed towards either an ‘inanimate’ object, such as sticks for apes and toys for children, or ‘animate’, such as touching others or self-grooming. The team found that there was a right-handed dominance only in actions towards inanimate objects. The identical video-sampling technique has been used by the study’s lead author, Dr Gillian Forrester of Westminster University, with groups of captive gorillas and chimpanzees observed in their enclosures. In these species, exactly the same pattern of context-sensitive handedness was observed. Right-handed actions appear to be related to tool use across species.
Professor Thomas said: “It is essential to take into account the context in which human behaviour occurs. Previously, researchers just looked at whether people used their left or right hand to perform an action. Because actions to objects are more frequent, it seemed as if we were mainly right handed. It’s only when you distinguish actions between those towards objects and those towards people that you realise that right-handedness is about tool use. It is extremely suggestive that this pattern is also observed in great apes. It suggests that the specialism of the left brain hemisphere for language in humans derived from its origins in sophisticated tool use.”
The authors of the research were Dr. Gillian Forrester of Westminster University, Dr. David Leavens of Sussex University, Caterina Quaresmini of the University of Trento, and Professors Denis Mareschal and Michael Thomas of Birkbeck College London. The research was funded by the European Commission and the UK Economic and Social Research Council.
‘Human Handedness: An inherited evolutionary trait’, by Gillian S Forrester, Caterina Quaresmini, David A Leavens, Denis Mareschal, Michael S C Thomas, is published in Behavioural Brain Research, October 2012.