The Origins Of Human Handedness

Nice, succinctly written piece on ScienceBlogs by Michael Balter on the evolution of human handedness. As has been pointed out in an earlier post here, humans are unique in having a species-wide handedness preference - 85% of all humans are right-handed, whereas, while other higher primate species do demonstrate handedness, it is not consistent and species wide. Balter reports the research and thoughts of University of Liverpool researcher Natalie Uomini who conducted a number of "stone age" tasks with children and adults and noted that while they might use either hand for simple tasks, they showed pronounced handedness preference the more complex the manual task became. It is as if, she says, "they had to make their minds up which hand to use" when confronted by complex manual tasks. Teaching of techniques via demonstration would also have maintained the hand preference because learners tend to copy the way the teacher's hands are used. Certainly there is strong evidence from skeletons for handedness in Neanderthals, and Homo heidelbergensis - so this dates back to at least 500,000 years, though Uomini, Balter reports, takes umbrage with Nick Toth's assertions that bias in the way flakes are shaved off stone tools suggests handedness as far back as Homo ergaster - about 1.6 million years ago. One expert flint maker, she says, could have made most of all flints found at a single camp and so it is wrong to represent the many flints found as separate data points. You cannot assume the hand preference extended to all individuals at the time.