So…Why Is The World Right-Handed?

    If you’re reading this on your phone, there is a 90% chance you are scrolling with your right hand. Roughly 85%-90% of people are right-handed, while just 10%-15% are the cool people…um, I mean, left-handed (how sad is that), and then a tiny percentage are ambidextrous show-offs! 

    Although the exact figures vary slightly from place to place, “no human population exists in which left-handedness is more common than right-handedness,” says Paul Rodway, a senior lecturer in psychology at the University of Chester in the United Kingdom, who studies handedness. So why do humans overwhelmingly favor the wrong hand? Ah, we kid because we…oh, never mind!

    Why don’t we take a look at that old chestnut, the “Nature vs. Nurture” argument, and see what that tells us! The environment you grow up in often plays some role in whether you’re right- or left-handed. In some Asian, African, and predominantly Arab countries, the left hand is considered “unclean” and children with a dominant left hand are forced to become right-handed through restraint and punishment. (Yes, Virginia. Some countries are not as culturally and intellectually advanced as others.) “Cultures where there is strong social pressure against left-handedness have lower rates of left-handedness,” says Rodway. And may I add, on a personal note, that Nonnie, my saintly, wonderful, loving, could do no wrong grandmother, would strike my left hand with a Thor-like hammer, over and over again when I was a child, in order to encourage me to use my right hand so I would be spared the persecution left-handed people like her faced when she was young! Really, Boss? Beaten with a hammer? By your saintly grandmother? Well, maybe gentle taps with a ruler, but that’s not the point! Moron… Anyway, even in societies that show no bias, lefties remain a clear minority. “This stable prevalence rate across cultures suggests a biological influence.”

    In fact, scientists think the tendency to prefer one hand over the other begins before birth. “This preference is already visible in the movements of unborn fetuses,” says Clyde Francks, a professor of brain imaging genomics at the Max Planck Institute and Radboud University Medical Center in The Netherlands. Ultrasound scans have shown that by the 10th week of gestation, most fetuses move the right arm more than the left, and from the 15th week most suck the right thumb rather than the left. “It is likely that right-handedness is the default outcome of early brain development as encoded by the genome,” according to Francks. Well, isn’t that disappointing. 

    Research suggests that dozens of genes—perhaps up to 40—play a role in shaping handedness. But rather than determining it outright, these genes build the brain in a way that typically favors the right hand as the dominant one, Francks explains. But if right-handedness is the brain’s default setting, my question is, what makes some people really cool…sorry, I mean left-handed? “We think that most instances of left-handedness occur simply due to random variation during development of the embryonic brain, without specific genetic or environmental influences,” says Francks. “For example, random fluctuations in the concentrations of certain molecules during key stages of brain formation” could influence which hand you write and throw with. Or maybe (being the cagey guy I am), those certain molecules indicate advanced intelligence, virility, and beauty…which then ‘programs’ the brain to favor the left hand! Seems simple enough to me. You’re left-handed aren’t you, Boss? Yes I am, Sancho…and damn proud of it! Why do you ask? Never mind. 

    Some scientists think most people are right-handed because it gave our ancestors an edge. One theory links handedness to tool use and the passing down of skilled movements across generations, according to Paul Rodway, a psychologist at the University of Chester in England. Archeological evidence backs that up: A 2011 study found that humans have strongly favored their right hand for tool use for at least half a million years. A textured photograph of a rock wall displays ancient cave paintings (rock art) in shades of sepia and brown. The paintings primarily depict scenes of human figures hunting stylized animals, including deer or elk, using bows, arrows, and spears…with those tools depicted in the right hand. Well, of course CAVEMEN were right-handed! What left-handed person doesn’t know that! My guess is that the left-handed cavemen, and cave-women, were off inventing the wheel, or those scissors with the green handles that made you feel awkward and different from the rest of the class back in elementary school, or maybe they were somewhere writing the first rudimentary blogs on stone tablets! You know…FromTheCave.rock! Idiot.

    Rodway and his collaborators have proposed another theory. “Right-handedness may have evolved, in part, due to humans fighting with sharp weapons. When facing an opponent, a right-hander is most likely to stab an opponent’s left thorax, where the majority of the heart is,” Rodway explains. So, let’s say during an ancient duel, “a right-hander may be more likely to kill an opponent than a left-hander would, because they penetrate the heart. This can result in a relative survival advantage for right-handers, and this may be one of the forces that led to the prevalence of right-handed humans.”

    Still, we lefties may have our own advantages. We excel in creative, as well as spatial thinking. And our rarity makes our movements harder to predict, which can be useful in both combat and sports. (Sneakiness and slyness as survival traits! Alright!) “This may have enabled left-handers to persist in human populations,” continues Rodway. “With such opposing advantages and disadvantages, evolution often settles on an equilibrium. This is what may have happened with the proportions of left- and right-handers in populations. However, more research is needed, because the picture is complex.” 

    So where does this brief, and admittedly incomplete story lead us? Cultural pressure can influence which hand people use, but the preference likely begins before birth. Dozens of genes involved in brain development create a natural bias toward the right hand, and over time, evolutionary forces such as tool use and combat may have strengthened that tendency. But never fear, my fellow lefties…we are the cool ones! Stay strong! He’s kidding, my bipedal friends…I think! 

Write to Peter: magtour@icloud.com