The team, who have today published the results of their study in Proceedings of the Royal Society B
, saw that left-handers had the advantage in sports such as fencing, tennis and baseball.
They said that Western interactive sports such as these can be classed as "special cases of fights - with strict rules, including the prohibition of killing and intentionally wounding the opponent".
This led them to speculate the same advantage may persist in more aggressive contexts, such as war, so societies which are more violent would have a higher frequency of left-handers.
|The suggestion that left-handers have an advantage in combat is not new. It has long been thought that, in the days when arguments were resolved by hand-to-hand combat, being left-handed gave people the benefit of surprise against a right-handed opponent. This advantage, however, would only have persisted if left-handers remained in the minority. Otherwise, right handers would soon get accustomed to fighting with left-handed opponents.
For this latest study, the researchers analysed data for eight traditional societies; the Kreyol people of Dominica, the Ntimu of Cameroon, the Dioula-speaking people of Burkina Faso, the Baka of Gabon, Inuit people and the Eipo people of Irian Jaya, New Guinea. Charlotte Faurie and Michel Raymond compared homicide rates (which includes murders and executions) and the frequency of left-handedness, and found they appeared to be linked.
The Dioula were found to have a homicide rate equivalent of one hundredth of a death per 1,000 people per year, and a left-handedness rate of just 3%.
But the Eipo had around three homicides per 1,000 people and a left-handedness rate of 20%.
Dr Faurie said "We have found a direct correlation between the level of violence in a given society and the proportion of left-handers. This indicates that fighting can be an important selection pressure in the evolution of left-handedness."
The researchers admitted that a homicide rate that includes executions and gang murders is probably not an accurate measure of one-to-one fights in society, but it was the best measure available. "This result strongly supports the fighting hypotheses. More generally, it points to the importance of violence in understanding the evolution of handedness in humans." she said.
Chris McManus, a professor of psychology at University College London who has made a study of the pros and cons of left-handedness, detailed in his book "Right Hand Left Hand", said it was true that left-handers did have an advantage in a fight - "It's the same advantage as you see with tennis players, baseball players and cricketers".
But he added: "The question is whether that advantage in fights then goes on and dominates the rate of left-handedness in societies, and I think the answer is 'no it doesn't'. The explanation must be much more complex than that."
There must have been an advantage for a minority of people to be born left-handed, but trying to find out what this advantage is remains unclear, he said. "The theory I've put forward is that despite the drawbacks of being left-handed, there are advantages in terms of creativity and other positive aspects," said the professor, "and society needs a subgroup who are different."
He added that the French study had also examined too few people, raising concerns over its conclusions. "The sample sizes were small and the methods they used were not as reliable as they could have been. I'm far from convinced" he said.
Left-Handers Club Comment:
The suggestions that left-handers have good combative skills is not unreasonable, and has been proven many times by the high number of successful left-handers in combative sports such as fencing, tennis, and boxing. See our list of famous left-handed sports players
What is interesting in this study is the suggestion that the instance of left-handers increases in a more violent society. There is no suggestion that the left-handers are the perpetrators of the violence, only that they are good fighters. Perhaps this is the key to their success, since they will have a kudos and elevated position in society, as well as longevity, enabling them to breed more successfully and pass on the left-handed genetic trait to more offspring.
Even if this were the case, however, the random nature by which left-handedness passes through generations (as detailed by Prof. McManus) would inhibit left-handers becoming the majority of the population, and thus losing their combative advantage.
Whilst this is an interesting hypothesis, the size and nature of the study do, as pointed out by Dr Chris McManus, undermine its credibility and a more controlled study on a far wider range of societies would be most welcome, to provide more reliable results.
BBC News - http://news.bbc.co.uk/go/pr/fr/-/1/hi/health/4073775.stm
New Scientist - http://www.newscientist.com/news/print.jsp?id=ns99996773
Chris McManus Book "Right Hand Left Hand" buy this book now in our online shop