Left-handers win in hand-to-hand combat~heather

By Will Knight

Left-handed people may be better equipped for close range mortal combat than those who rely on their right hands, according to researchers.

Charlotte Faurie and Michel Raymond of the University of Montpellier in France examined the number of left-handed people in unindustrialised cultures as well as the homicide levels within each culture.

They discovered a correlation between levels of violence and the proportion of the left-handed population – the more violent a culture, the higher the relative proportion of left-handers. The cause for this, the researchers suggest, is that left-handers are more likely to survive hand-to-hand combat.

The news could provide comfort for those who routinely struggle with right-handed scissors and can-openers, but some experts are unconvinced by the link.

Left-handed people are more prone to some health problems, suggesting the trait ought to disappear naturally over many generations through natural selection. But left-handers continue to make up a small proportion of the human population, hinting there could also be some evolutionary advantage to being left-handed.

And the ratio of left-handers to right-handers is higher in successful sportspeople than it is in the general population, suggesting there is definite advantage to favouring the left hand or foot in competitive games, such as tennis.

Homicidal tendencies

"Because of the advantage in sports we thought there could be a similar advantage in fights," Faurie told New Scientist . The theory is that right-handed competitors are less accustomed to facing left-handers, making them a more difficult proposition.

Faurie and Raymond studied several unindustrialised societies with varying rates of homicide, using their own fieldwork and ethnographic literature. They excluded industrialised cultures due to a lack of data and because, they argue, use of firearms is unaffected by handedness.

At one end of the scale, their sample included the Dioula of Burkina Faso, where just 3.4% of the population is left-handed and there are only 0.013 murders per 1000 inhabitants each year. At the other end of their sample spectrum, they studied records of the Eipo of Indonesia, where 27% of the population is left-handed and the homicide rate is considerably greater - three murders per 1000 people each year.

The strong correlation between the proportion of left-handers and the number of homicides in each culture suggests that left-handers are more likely to survive a fight, they say. "It could be one of the reasons left-handedness has survived," Faurie says. "Though there may be other reasons too."

Brain differences

Daniel Nettle, an expert in human evolutionary history at the University of Newcastle-Upon-Tyne, UK, is intrigued. "The results quite surprised me," he says. "But I can't think of any reason why they might be an artefact [of the study design], so it looks like an interesting finding."

However, Chris McManus at University College London, who has researched handedness, is more sceptical about the link. "I'm far from convinced," he told New Scientist . "I don't think it is anything as simple as this."

McManus says the sample data is too small provide firm evidence of a connection between handedness and fighting prowess and says data from western societies should also have been included.

He believes the success of left-handers may be largely due to differences in the brain. "It may be that sometimes their brains assemble themselves in combinations that work better for certain tasks," he says.

Journal reference: Proceedings of the Royal Society B (DOI: 10.1098/rspb/2004/2926)

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