The fighting hypothesis is a major hypothesis on the evolution of left-handedness.

A new publication presents the modified fighting hypothesis.

The modified fighting hypothesis assumes that right-handers have an evolutionary advantage.

The fighting hypothesis is one of the major theories on the evolution of left-handedness.

Around the world, about 10.6% of people are left-handers, and the rest are right-handers. Many scientists have developed ideas and theories on the evolution of right- and left-handedness that are aimed at explaining this peculiar pattern. One of the leading ideas is the so-called fighting hypothesis.

The fighting hypothesis (Raymond and co-workers, 1996) proposes that there is a so-called frequency-dependent maintenance of left-handedness. The main idea is that over the tens of thousands of years of human evolution, left-handers did have an advantage in fights due to a surprise effect. This gives them an evolutionary survival benefit since they win more fights. This surprise effect emerges since most people would expect their opponent in a fight to be right-handed and attack mainly with the right hand, so they may be taken by surprise if the fight is with a left-handed person. While this hypothesis is supported by some data from combat sports and other sources, it has been criticized for only focusing on left-handers and not really explaining why most people are right-handed.

A new theory on the evolution of right- and left-handedness

Now, a new scientific article entitled “The modified fighting hypothesis of handedness: Evidence from sharp force injuries and further considerations” presents a new form of the fighting hypothesis, the so-called modified fighting hypothesis. In contrast to the original fighting hypothesis, this new version explains the evolution of both right- and left-handedness (Rodway and co-workers, 2026). In the scientific article published in the journal Laterality, the research team, led by scientist Paul Rodway from the University of Chester in the U.K., laid out the reasons why, over the course of human evolution, right-handers may, on average, have an advantage in fighting situations compared to left-handers, to explain why most people are right-handed and not left-handed.

The core assumption of the modified fighting hypothesis is that fights with sharp weapons may be the key to understanding why most people are right-handed. Specifically, the modified fighting hypothesis assumes that right-handers may have an evolutionary advantage since, due to the position of the heart on the left side of the body, they have a higher chance of severely injuring or killing their opponent in fights with sharp weapons like knives. Simply put, when an opponent stands opposite to a right-hander and the right-hander stabs them with a knife, they are more likely to injure the heart of their opponent, which is located on the side of their dominant hand, than a left-hander. It has to be kept in mind that theories like this explain the emergence of handedness over the course of tens of thousands of years of evolution, in which violent fights with sharp weapons were more common than today.

The scientists bring forward several facts from other scientific studies that support this idea:

In records of violent crimes, the right upper body is stabbed 2.4 times more often than the left upper body, most likely because most people are right-handed. This shows that right-handers are indeed more likely to hit the left upper body of their opponent in fights with sharp weapons.

Right-handers are more likely to stab the left side of their opponents' bodies.

Two-thirds of the heart is in the left half of the body.

A stab to the left upper body is more lethal than one to the right upper body.

Taken together, these facts result in a strong evolutionary survival benefit for right-handers during human evolution. However, as suggested by the original fighting hypothesis, left-handers retain an evolutionary survival advantage of their own as long as they are rare due to a surprise effect in fights. While further empirical research is needed to test the modified fighting hypothesis, it is a promising idea to fill a major gap in understanding the evolution of handedness.

Raymond, M., Pontier, D., Dufour, A. B., & Møller, A. P. (1996). Frequency-dependent maintenance of left handedness in humans. Proceedings. Biological sciences, 263(1377), 1627–1633. https://doi.org/10.1098/rspb.1996.0238

Rodway, P., Larsson, M. L., & Schepman, A. (2026). The modified fighting hypothesis of handedness: Evidence from sharp force injuries and further considerations. Laterality, 1–51. Advance online publication. https://doi.org/10.1080/1357650X.2026.2638523

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