Left-Handed Anomalies -- Why?

 

"Houston’s Yordan Alvarez might be the top left-handed hitter in Major League Baseball. Teammate Framber Valdez ranks among the best left-handed pitchers, too.

"Other than that, those guys are all right.

"Literally — neither player considers himself left-handed at all.

"MLB and its history are dotted with men who played out of their natural handedness, a phenomenon that is seen occasionally in other sports but is a regular occurrence on the diamond. Thumb through a pack of baseball cards from just about any era and you’re likely to see players who bat one way and throw the other. Ask them to sign that card and there’s no telling which hand would hold the pen.

"Valdez writes, eats and even hits (before the introduction of the universal designated hitter) with his right hand. His left arm has helped him make two All-Star teams and throw a no-hitter. What else does he use it for?

“'Nothing, nothing, nothing,' he said with a laugh.

"Valdez simply decided at a young age that he wanted to be a left-handed pitcher.

“'I used to throw lefty every single day, like day by day by day,” he said in Spanish through a translator. 'When I was 11, I felt very comfortable throwing lefty, even though I did everything else righty.'”

(Kristie Rieken. "Who’s really left-handed? In baseball, it can be hard to tell." AP. https://apnews.com/article/mlb-left-handed-4eb62b7acebb3d0e5617bf49b3925049. April 9, 2024.)

Dr. Stephen D. Christman, a professor in the psychology department at the University of Toledo and an expert in handedness, said cases like those aren’t that surprising.

“It’s easier for a lefty to learn to use their right hand than for a righty to learn to use their left hand because most left-handers lean more towards being ambidextrous,” said Christman, who has studied handedness for more than two decades.

Christman said studies have found only 1-2% of people are uniformly left-handed across the 10 activities used to measure handedness, including writing, drawing, throwing, brushing teeth and hair, opening a box and using a spoon. Because lefties are forced to adapt — like when only righty scissors are available — they’re more likely to learn to use both hands.

(Kristie Rieken. "Who’s really left-handed? In baseball, it can be hard to tell." AP. https://apnews.com/article/mlb-left-handed-4eb62b7acebb3d0e5617bf49b3925049. April 9, 2024.)

Go back in history and we find famous lefties like * Charlemagne and Leonardo da Vinci. However, Time Magazine (1969) reported southpaws were once seen as sinister -- "literally, since the word means 'left' -- for centuries. 'In the Middle Ages, for instance, the left-hander lived in danger of being accused of practicing witchcraft," the article explained. "The Devil himself was considered a southpaw, and he and other evil spirits were always conjured up by left-handed gestures.”

 (Lilly Rothman. "How Lefties First Gained Acceptance. TIME. August 13, 2015.)

 * Other famous lefties include Aristotle, Oprah Winfrey, Napoleon Bonaparte, Bill Gates, and Jimi Hendrix. Among U.S. presidents being left handed is nothing new. Barack Obama is the latest to join a long list of left-handed presidents from the 20th century: James Garfield, Herbert Hoover, Harry Truman, Gerald Ford, Ronald Reagan, George H.W. Bush and Bill Clinton were all southpaws.

Why the change of the suspicion in public opinion about left-handers? TIME suggested, it was a lot less complicated than anything having to do with evil spirits. It was just a matter of simple economics. 

At the time, lefties had few options in terms of the everyday items that depend on handedness; from sports equipment to kitchen items, most things designed to be held were only optimized for one direction. That situation meant there was an untapped market for leftie goods, just waiting for a smart business owner to jump. And jump they did: a few shops now cater to left-handers who either cannot or will not adjust to a right-handed world. One of the most interesting—run by a righthander, surprisingly—is Anything Left-Handed, Ltd. in London’s West End. 

Smithsonian Magazine reports that the world has gotten progressively more accepting of left-handed folk, but there are still some undeniable bummers  associated with a left-handed proclivity: "desks and spiral notebooks pose a constant battle, scissors are all but impossible to use and–according to some studies–life expectancy might be lower than for right-handed people."

What makes humanity’s bias against lefties all the more unfair is that left-handed people are born that way. In fact, scientists have speculated for years that a single gene could control a left-right preference in humans. Unfortunately, they just couldn’t pinpoint exactly where the gene might lie.

(Natasha Geiling. "Why Are Some People Left-Handed?" https://www.smithsonianmag.com/science-nature/why-are-some-people-left-handed-6556937/. Smithsonian Magazine. September 12, 2013.)

Now, in a paper published  in PLOS Genetics a group of researchers have identified a network of genes that relate to handedness in humans. What’s more, they’ve linked this preference to the development of asymmetry in the body and the brain.

The hypothesis is a logical response to a key question: If handedness is genetic and if right-handedness is such a dominant trait, why hasn’t left-handedness been forced out of the genetic pool? In reality, the research suggests that handedness could be more subtle than simple “dominant” or “recessive” traits–a whole host of genes might play significant roles.

( William M. Brandler, Andrew P. Morris, David M. Evans, Thomas S. Scerri, John P. Kemp, Nicholas J. Timpson, Beate St Pourcain, George Davey Smith, Susan M. Ring, John Stein, Anthony P. Monaco, Joel B. Talcott, Simon E. Fisher, Caleb Webber, Silvia Paracchini. "Common Variants in Left/Right Asymmetry Genes and Pathways Are Associated with Relative Hand Skill."12 Sep 2013 PLOS Genetics.)

(Anil Chougule, François Lapraz, István Földi, Delphine Cerezo, József Mihály, Stéphane Noselli. "The Drosophila actin nucleator DAAM is essential for left-right asymmetry." Research Article | published 23 Apr 2020 PLOS Genetics.)

 

William Brandler, a PhD student at Oxford University and the paper’s lead author, is confident that even if environmental factors (like the continued hatred of lefties by two-thirds of the world)  place pressure on handedness, any baseline bias still boils down to genetics. “People think it’s just an environmental thing, but you’ve got to think, why is there that initial bias in the first place, and why do you see that bias across all societies? Why aren’t there societies where you see a bias to the left?” Brandler asks.  

The global average of lefties comes in at 10-12 percent. A study in the journal Endeavor recently took on this question: Why are there no left-handers in China? The researchers also looked at India and Islamic countries and discovered that nearly two-thirds of the world’s lefty population faces discrimination.

(Rose Eveleth. "Two-Thirds of the World Still Hates Lefties." Smithsonian Magazine. May 17, 2013.)

(Howard I. Kushner. "Why are there (almost) no left-handers in China?" Endeavour. Volume 37, Issue 2. June 2013.)

 "Why are there so few Chinese left-handers?" has a number of possible answers, including that there are and always have been many left-handers in China, but that the way they were measured determined their prevalence. Alternatively, the differences could be real because as we saw with China, a combination of traditional values and practical considerations seem to have merged to reduce the reported prevalence of left-handedness.

Conclusions

Overall 40% of us are left-eared, 30% are left-eyed and 20% are left-footed. But when it comes to handedness, only approximately 10% of people are lefties.Why could this be? Why are left-handers in the minority?

 In times gone by, left-handedness was drummed out of errant schoolchildren, and oddly negative connotations still linger in our language. The word "left" comes from the Anglo-Saxon word "lyft," meaning "weak." And the opposite in Latin is "dexter" which is associated with skill and righteousness.

So what determines whether we are right- or left-handed? From an evolutionary standpoint, specializing with one hand makes sense. Chimpanzees tend to choose a favorite hand for different tasks.

Human ancestry and tracking? Take termite fishing. After selecting the perfect stick, the chimp pokes it into the termite mound, their sense of touch providing a host of information about how deep, wide and full of tasty termites their house may be. Then they’ll gently pull the stick out to reveal their prey, the termites’ jaws clamping down hard on the foreign invader. Unbeknown to them, they are about to get chomped by a hungry chimp. By specializing with one hand, chimps become more dexterous, and more termites bite the dust.

But when primatologists study chimpanzees in the wild, their patterns of handedness look very different to ours. For each task around 50% are right-handed, and 50% left. So where in our evolutionary tree does this 1 in 10 ratio emerge?

An important clue comes from Neanderthals’ teeth. Neanderthals, it turns out, were clever, but clumsy. Our ancestors used their teeth to anchor slabs of meat, whilst they held a knife in their dominant hand to carve it up. Now and again, they would scratch their teeth. The distinctive pattern of grooves in their front incisors reveals which hand must have been holding the food, and which was grasping the knife. Incredibly, when you compare the number of left- and right-handed Neanderthals, this same ratio of 1 in 10 left-handers that we see today pops out.

Consider this amazing fact: babies in the human womb develop preferences. Peter Hepper, from Queen's University in Belfast, has done some wonderful ultrasound studies looking at babies’ movements inside the womb.

He found that nine out of 10 fetuses preferred sucking their right thumb, mirroring the familiar pattern we see in the general population. And when he followed those children up many years later, the babies who were sucking their right thumb in the womb became right-handed, and the ones who preferred their left, stuck with that.

(Hannah Fry. "The mystery of why left-handers are so much rarer." BBC. https://www.bbc.com/future/article/20160930-the-mystery-of-why-left-handers-are-so-much-rarer. October 3, 2016.)

Still interested in the left-handed mystery. Or, are you worn out? Read this abstract from the National Library of Medicine and see if any of this makes sense to you. As for me, I'm glad the stigma in my country is gone, but I am fascinated at how much of it remains elsewhere. Tradition, genes, customs? I haven't much more than a few clues to the cause of the small number of lefties roaming the world. Did you ever wonder? Now you know and can do more research on your own ... especially you minority numbers of left-handers.

Abstract

"Although most people are right-handed and have language in their left cerebral hemisphere, why that is so, and in particular why about ten per cent of people are left-handed, is far from clear. Multiple theories have been proposed, often with little in the way of empirical support, and sometimes indeed with strong evidence against them, and yet despite that have become modern urban myths, probably due to the symbolic power of right and left. 

"One thinks in particular of ideas of being right-brained or left-brained, of suggestions that left-handedness is due to perinatal brain damage, of claims that left-handers die seven years earlier than right-handers, and of the unfalsifiable ramifications of the byzantine Geschwind-Behan-Galaburda theory. 

"This article looks back over the past fifty years of research on brain asymmetries, exploring the different themes and approaches, sometimes in relation to the author’s own work. 

"Taking all of the work together it is probable that cerebral asymmetries are under genetic control, probably with multiple genetic loci, only a few of which are now beginning to be found thanks to very large databases that are becoming available. 

"Other progress is also seen in proper meta-analyses, the use of fMRI for studying multiple functional lateralisations in large number of individuals, fetal ultra-sound for assessing handedness before birth, and fascinating studies of lateralisation in an ever widening range of animal species. With luck the next fifty years will make more progress and show fewer false directions than had much of the work in the previous fifty years."

 (Chris McManus. "Half a century of handedness research: Myths, truths; fictions, facts; backwards, but mostly forwards." Brain Neurosci Adv. Jan-Dec 2019. 3: 2398212818820513.)