Opponents simply do not expect a left-hook.
The endurance of left-handedness has puzzled researchers, because it is linked to disadvantages including an increased risk of some diseases.
But University of Montpellier experts, writing in Proceedings B, say it could be because they do well in combat.
The team 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 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.
They looked at homicide-rates 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%.
Chris McManus, a professor of psychology at University College London who has made a study of the pros and cons of left-handedness, 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."
Professor McManus said the more likely explanation for the persistence of left-handedness was the need for individuals with a range of qualities and skills within societies.
He added that the French study had also examined too few people, raising concerns over its conclusions.