Cooperation favors same-handedness—for sharing the same tools, for example.
Left-handed people are relatively rare because of the balance between cooperation and competition in human evolution, according to a new study of sports data.
Representing only 10 percent of the general human population, left-handers have been viewed with suspicion and persecuted across history. The word “sinister” even derives from “left or left-hand.”
Researchers at Northwestern University now report that a high degree of cooperation, not something odd or sinister, plays a key role in the rarity of left-handedness.
They developed a mathematical model that shows the low percentage of lefties is a result of the balance between cooperation and competition in human evolution.
Professor Daniel M. Abrams and graduate student Mark J. Panaggio—both right-handers—are the first to use real-world data (from competitive sports) to test and confirm the hypothesis that social behavior is related to population-level handedness.
The results are published this week in the Journal of the Royal Society Interface.
“The more social the animal—where cooperation is highly valued—the more the general population will trend toward one side,” said Abrams, an assistant professor of engineering sciences and applied mathematics at the McCormick School of Engineering and Applied Science. “The most important factor for an efficient society is a high degree of cooperation. In humans, this has resulted in a right-handed majority.”