Out of every 10 people, 9 are right-handed – a disparity that researchers have been trying to explain for decades without concrete results.
One of the ideas considered a combat hypothesis suggests that: “Left-handedness provides an advantage in fighting, although the overall impact on physical health makes left-handed individuals rarer in the population.” In reality, men – who have historically led in competitions for resources and mates – have a higher rate of left-handedness compared to women.
Illustration of an ancient person holding a spear with their right hand. (Photo: Bigthink).
However, studies show that left-handed individuals often excel compared to their right-handed counterparts, particularly in sports that require hand-eye coordination, such as tennis, volleyball, and baseball. This may be due to the fact that players are not accustomed to competing against left-handed opponents, as they are less common.
A significant issue with the combat hypothesis is that the anticipated health disadvantages have not been substantiated in large studies. Overall, left-handed individuals do not appear to be affected by health issues more than right-handed individuals, and their lifespan does not seem shorter.
Recognizing this clear issue, a team of three scientists from Lund University (Sweden) and Chester (UK) has proposed an updated version of the combat hypothesis that aligns better with current data. In a paper published in the journal Symmetry, scientists Matz Larsson, Astrid Schepman, and Paul Rodway argue: “Throughout human history, right-handed individuals have had a significant combat advantage, which is why they are more numerous.”
The question arises: why do right-handed individuals have a combat advantage? According to the researchers, this relates to the position of the heart and the belief that humans have conducted most confrontations with sharp handheld weapons, such as wooden spears, throughout much of human history.
About three-quarters of the heart is located on the left side of the chest, making the left side of the torso a more vulnerable target. The researchers note that when fighting with stabbing weapons, the hand used to hold the weapon determines which area of the chest is exposed to the opponent. Holding a weapon in the left hand will rotate the left side of the chest toward the enemy, thereby exposing a larger portion of the heart. In contrast, holding a weapon in the right hand will rotate it away from the enemy. Furthermore, the left arm can be used to block the opponent’s stabbing attacks during combat.
In summary, this means that right-handed individuals may be better protected from lethal stabbing attacks.
Based on the new version of the combat hypothesis, an important prediction can be made: “Since there are no health disadvantages associated with left-handedness and fighting with stabbing weapons is no longer an evolutionary pressure, we may see the proportion of left-handed individuals in modern societies remain stable or increase significantly.” Some studies suggest that the rate of left-handed individuals has increased in the 20th century, but it remains unclear whether this is due to genetics or culture.
It is important to note that the new explanation for the advantages of right-handed individuals is still a hypothesis, based on deductions from physiological events and behavioral anecdotes, supported by large observational datasets. The updated combat hypothesis is plausible, but it has yet to be proven.
