A new research hypothesis suggests that the ratio of left-handed and right-handed individuals is tied to the way in which our society competes and cooperates.
Researchers began the study by a review of left-handedness. Lefties represent only 10 percent of the general human population, a ratio that has remained constant for more than 5,000 years.
Investigators developed a mathematical model that shows the low percentage of lefties is a result of the balance between cooperation and competition in human evolution. That is, the need for cooperation within a society plays a key role in the rarity of left-handedness.
In the study, Daniel M. Abrams, Ph.D., and Mark J. Panaggio use real-world data (from competitive sports) to test and confirm the hypothesis that social behavior is related to population-level handedness. Their findings are the first to be supported by “live” data.
The results are published 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. “The most important factor for an efficient society is a high degree of cooperation. In humans, this has resulted in a right-handed majority.”
For example, in a cooperative environment, individuals would share – in the case of a evolving population, this could mean sharing the same tools improving efficiency and effectiveness. Physical competition, on the other hand, favors the unusual. In a fight, a left-hander in a right-handed world would have an advantage.
Although societies are generally cooperative, some competition tends to exist. If a society was totally cooperative then everyone would be same-handed, explains Adams. Contrarily, if competition were more important, one could expect the population to be 50-50.
According to the authors, the new model can predict accurately the percentage of left-handers in a group — humans, parrots, baseball players, golfers — based on the degrees of cooperation and competition in the social interaction.
Researchers say the model helps to explain our right-handed world now and how the 9-1 right-handed to left-handed ratio has remained stable over thousands of years.
The model also explains the dominance of left-handed athletes in many sports where competition can drive the number of lefties up to a disproportionate level.
To prove the accuracy of the model, Abrams and Panaggio turned to the world of sports for data to support their balance of cooperation and competition theory.
Their model accurately predicted the number of elite left-handed athletes in baseball, boxing, hockey, fencing and table tennis — more than 50 percent among top baseball players and well above 10 percent (the general population rate) for the other sports.
On the other hand, the number of successful left-handed PGA golfers is very low, only 4 percent. The model also accurately predicted this.
“The accuracy of our model’s predictions when applied to sports data supports the idea that we are seeing the same effect in human society,” Abrams said.
Handedness, the preference for using one hand over the other, is partially genetic and partially environmental. Identical twins, who share exactly the same genes, don’t always share the same handedness.
“As computers and simulation become more widespread in science, it remains important to create understandable mathematical models of the phenomena that interest us, such as the left-handed minority,” Abrams said.
“By discarding unnecessary elements, these simple models can give us insight into the most important aspects of a problem, sometimes even shedding light on things seemingly outside the domain of math.”
Source: Northwestern University