Study Shows That Left-handers Are Not the Product of Witchcraft After All

05/02/2012 04:58 pm ET Updated Jul 02, 2012

A new study at Northwestern University shows that left-handedness is the product of cooperation and competition in evolution (see ScienceDaily, "Shedding Light On Southpaws: Sports Data Help Confirm Theory Explaining Left-Handed Minority in General Population").

Being left-handed, I am among the minority of the population (10 percent), and this study by Daniel M. Abrams and Mark J. Panaggio (see "A Model Balancing Cooperation and Competition Can Explain Our Right-handed World and the Dominance of Left-handed Athletes" in The Journal of the Royal Society Interface) shows why. The highly social nature of humanity tends toward cooperation, and in this case, this means right-handedness.

Life is probably much easier, of course, when we can all use the same scissors.

However, not all of us wish to cooperate and, in fact, competition is necessary for evolution as well -- that's where us lefties come into the picture. "If societies were entirely cooperative everyone would be same-handed," ScienceDaily reports. "The new model can predict accurately the percentage of left-handers in a group -- humans, parrots, baseball players, golfers -- based on degrees of cooperation and competition in the social interaction."

Studies of the evolutionary advantages of cooperation are prominent, particularly in terms of survival. In one recent study (Proceedings of the Royal Society B), for example, it has been shown that social interaction and cooperation led to the evolution of intelligence and larger brain sizes. And just in terms of being practical, successful hunting and the ability to avoid becoming the one hunted, is more likely when everyone works together.

"Social life is give and take, cooperation and competition," writes Todd Tremlin in his book Minds and Gods, "and it is crucial that individuals have a way to understand and predict the complex behaviors of those with whom they have contact." When there is confusion and unpredictability, this can threaten survival. In the case of anyone that does not fit cultural norms, this can lead to suspicion by the majority.

Enter the left-handed.

Aside from our usual difficulties -- virtually everything in the world is made for right-handers -- left-handed individuals have a history of being seen as problematic. Merriam-Webster's offers the definitions of "left-handed" as clumsy, awkward, insincere, and dubious. And this idea was reinforced through the middle of the 20th century when it was still common for teachers to push lefty students to overcome their dominant hand by writing with their right hands.

The left-handed have been referred to as sinistrals (meaning "inclined to the left"), which is related to "sinister," meaning unlucky, evil, or bad omen. Common phrases like, "left-handed compliment," for example, mean that which appears like a compliment, but is in reality a slight or that which really has evil intentions.

Religions can, though not always, depict being to the left as in a place of judgment. In the New Testament book of Matthew (25:41), for example, those who are put to the left hand of God are "accursed" and told to "depart... into the eternal fire prepared for the devil and his angels." The Old Testament book of Ecclesiasties says that "The heart of the wise inclines to the right, but the heart of a fool to the left," where to be on the left is clearly a bad thing. And in ascetic Buddhism, the "left hand path" is the wrong one, the fleshly, and the route of magic.

But this Northwestern study shows that left-handedness is not about being cursed, evil, or even clumsy (plenty of right-handers are that too). Being left-handed is not even purely the product of one's genes, as identical twins may not have the same dominant hand. (Studies do show that among those with ADHD, dyslexia, and schizophrenia there is a higher number of left-handers, but it is also believed that this might have something to do with prenatal stress.) Rather, the Northwestern study shows that "population-level hand preference represents a balance between selective costs and benefits arising from cooperation and competition in human evolutionary history."

Testing their mathematical model, Abrams and Panaggio, turned to sports. Upfront with their limitations, they acknowledge that "sports data may not be completely analogous to data from the natural world; hence, further quantitative analysis of lateralization in social animal groups may be a fruitful line of future research."

Nevertheless, "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."

So being left-handed is really just a plus for society. We are the southpaws that mess with the rules of engagement in a right-handed world. We make the world more interesting and force everyone else keep their eyes on the ball.