Lefties face worse disadvantages in life than struggling with tin openers, guitars, scissors and golf clubs designed for the right-handed majority.

  

Statistical evidence links several auto-immune diseases, such as inflammatory bowel syndrome and ulcerative colitis, with left-handedness.

  

Under Charles Darwin's principles of evolution, genes that hamper survival of the species should get weeded out. So it is a small mystery as to why the left-handed have not gone the way of the dinosaurs.

  

French anthropologists believe they have the answer: Left-handedness, far from being a disadvantage, is an evolutionary boon.

 

Theory

  

Their theory is that left-handers have survived - and in some cultures thrived - because they are better at fighting, having a built-in advantage in combat with a right-handed opponent.

 

Charlotte Faurie and Michel Raymond, of the Institute of Evolutionary Sciences at the University of Montpellier in southern France, compared the number of left-handed people with the number of homicides in eight traditional societies where the weapon was a knife or a machete.

  

"Left-handers have an advantage in sports involving dual confrontations, such as fencing, tennis and baseball (pitchers against batters) but not in non-interactive sports such as gymnastics"

UK Royal Society report

They analysed data from eight societies: The machete-wielding Kreyol of Dominica; the Ntumu of Cameroon; the Dioula-speaking people of Burkina Faso; the Baka in Gabon; the Eipo of West Papua; and Inuit people in Alaska, Greenland and Canada; the Jimi of Papua New Guinea and the Yanomamo of Venezuela.

  

The societies which had the most killings had the most left-handed people, they found. At the most peaceful end of the scale, the Dioula had a homicide rate of only one hundredth of a death per 1000 people per year, and left-handedness occurred only among 3% of the population.

  

At the other end of the scale, the Yanomamo had four homicides per 1000 inhabitants per year, while left-handers accounted for a huge 22.6% of their population.

 

Reservations

  

Faurie and Raymond do not say that to be left-handed is a source of violence and they stress that violence can also have a range of complex causes.

  

What the data does imply is that the genes for left-handedness have survived because, quite literally, in distant past, they helped their owners survive in the human jungle.

 

"This result strongly supports the fighting hypothesis," the pair said. "More generally, it points to the importance of violence in understanding the evolution of handedness."

  

Traditional advantage

 

The idea behind their theory - published on Wednesday in Proceedings B of the UK's Royal Society - comes from sport, where the southpaw technique often gets the better of confused right-handers.

  

"Lefthanders have an advantage in sports involving dual confrontations, such as fencing, tennis and baseball (pitchers against batters) but not in non-interactive sports such as gymnastics," the study says.

  

The research was tested only on traditional societies where there was a likelier risk of one-on-one combat, rather than in industrialised societies.

  

In hi-tech cultures, the theoretical advantage enjoyed by lefthanders would be cancelled out by long-range weapons.