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Why are some people left-handed? Here's what science has discovered
Why is only 10% of the population left-handed? There are a few new scientific clues pointing to the answer.
There is a small sect of our population that is left-handed. Researchers have found that 10 to 15 percent of people have an inborn proclivity for left-handed dominance. We know that it is in a sense rare and also lends itself to making lefties more creative and musically gifted, but we’re still stumped on what actually makes people left-handed when the majority of the populace is right-hand dominant.
The science behind why people are left-handed isn’t in agreement just yet. There have been a number of worthy studies and hypotheses put forth that deal with genetic differences and brain structure, and new research has begun to expand on those genetic and brain factors.
While scientists cannot yet confirm the definite point of handedness, they do know that children of left-handed parents are more likely to inherit this trait. There are also a few new scientific clues pointing the way ahead.
Scientific origins of left-handedness
A research paper in Nature put forth the idea that determining handedness could be done by analyzing prenatal development in humans. They hypothesized that if humans are congenitally prepared to a certain handedness then this type of wiring should be able to be examined in their motor system before birth.
The researchers tested this through ultrasonography and the results were promising. They stated that: “We revealed that both right-handed and left-handed fetuses were faster to reach to targets requiring greater precision (i.e., eye and mouth) with their dominant (vs. non-dominant) hand.”
This somewhat confirms the genetic factors—but there’s still more to the scientific story of left-handedness.
Symmetry and asymmetry throughout the body
Neuroscientists know that the reversal control in brain hemispheres tends to make left-handed people more “right-brained” (so to speak) and use this hemisphere of their cerebrum more than right-handed people and vice versa.
A right-brain dominant person does have some advantages in a few areas, but scientists have shown that having an equal symmetry and balance between all four brain hemispheres is of the most benefit. It’s thought that lefties have an overall greater brain symmetry, but the onset of left-handedness might start elsewhere and be actually due to asymmetry in a different part of the body.
The motor cortex in the brain controls arm and hand movements. It sends signals from this area of the brain into the spinal cord, which then makes the movement function into motion. The spinal cord and this part of the brain aren’t connected right away. It’s been shown that before this connection is made, dominant hand preferences are already becoming apparent.
Some scientists think that the root of the connection lies in the spinal cord. Researchers at the University of St. Andrews in Scotland tested out asymmetry in the body to better understand left- and right-handedness. They looked at a rare condition called situs inversus, which means all the major organs are reversed on the other side of the body. They figured out that parts of the genetic code for this rare condition could be found affecting left-handedness as well.
A lot of this research could be guiding us to an eventual comprehensive overview of why some of us are left-handed, a question that has been with us for some time.
Famous left-handed people
For some reason, there has usually been a connotation of wrongness or strangeness in the etymology of most languages’ definition of lefties. For example, the Latin words sinistral (left) and dexter (right) are the root words for sinister and dexterous.
Although lefties had to deal with this inherent cultural bias, throughout the years many of them have blazed forth paths that led them to riches and genius-level fame. Science is proving that growing up a lefty makes you creative and more likely to think outside the box. Here’s just a couple of famous figures to prove that fact.
Leonardo da Vinci, the prototypical Renaissance man, took his left-handedness to the extreme. In his immensely creative brain, he created his own idiosyncratic way of writing from right to left. You’d have to look through a mirror to read his script. He might have done this just to avoid messing up the ink on the paper while he wrote.
See the backward numbers? A famous example of Davinci's 'mirror writing', dated 1493-1505. (Source: Public domain)
Napoleon Bonaparte, another lefty, once objected to the military tradition of marching on the left side of the road and holding your weapon in the right hand. Legend says that once Napoleon was in power, he made all his armies switch sides, which then explains where our rules of the road came about.
A great deal of American presidents have also been left handed. Barack Obama was our latest, who was preceded by the likes of Bill Clinton, George H.W. Bush, Ronald Reagan, Gerald Ford, Harry Truman, Herbert Hoover and James Garfield in the 20th century.
While the science remains an unfolding mystery, the implications of left-handedness range from intense creative prowess and unexpected sleight of hand in both sport and politics.
There is a definite and unique advantage to being left-handed.
Join Pulitzer Prize-winning reporter and best-selling author Charles Duhigg as he interviews Victoria Montgomery Brown, co-founder and CEO of Big Think, live at 1pm EDT tomorrow.
Richard Feynman once asked a silly question. Two MIT students just answered it.
Here's a fun experiment to try. Go to your pantry and see if you have a box of spaghetti. If you do, take out a noodle. Grab both ends of it and bend it until it breaks in half. How many pieces did it break into? If you got two large pieces and at least one small piece you're not alone.
But science loves a good challenge<p>The mystery remained unsolved until 2005, when French scientists <a href="http://www.lmm.jussieu.fr/~audoly/" target="_blank">Basile Audoly</a> and <a href="http://www.lmm.jussieu.fr/~neukirch/" target="_blank">Sebastien Neukirch </a>won an <a href="https://www.improbable.com/ig/" target="_blank">Ig Nobel Prize</a>, an award given to scientists for real work which is of a less serious nature than the discoveries that win Nobel prizes, for finally determining why this happens. <a href="http://www.lmm.jussieu.fr/spaghetti/audoly_neukirch_fragmentation.pdf" target="_blank">Their paper describing the effect is wonderfully funny to read</a>, as it takes such a banal issue so seriously. </p><p>They demonstrated that when a rod is bent past a certain point, such as when spaghetti is snapped in half by bending it at the ends, a "snapback effect" is created. This causes energy to reverberate from the initial break to other parts of the rod, often leading to a second break elsewhere.</p><p>While this settled the issue of <em>why </em>spaghetti noodles break into three or more pieces, it didn't establish if they always had to break this way. The question of if the snapback could be regulated remained unsettled.</p>
Physicists, being themselves, immediately wanted to try and break pasta into two pieces using this info<p><a href="https://roheiss.wordpress.com/fun/" target="_blank">Ronald Heisser</a> and <a href="https://math.mit.edu/directory/profile.php?pid=1787" target="_blank">Vishal Patil</a>, two graduate students currently at Cornell and MIT respectively, read about Feynman's night of noodle snapping in class and were inspired to try and find what could be done to make sure the pasta always broke in two.</p><p><a href="http://news.mit.edu/2018/mit-mathematicians-solve-age-old-spaghetti-mystery-0813" target="_blank">By placing the noodles in a special machine</a> built for the task and recording the bending with a high-powered camera, the young scientists were able to observe in extreme detail exactly what each change in their snapping method did to the pasta. After breaking more than 500 noodles, they found the solution.</p>
The apparatus the MIT researchers built specifically for the task of snapping hundreds of spaghetti sticks.
(Courtesy of the researchers)
What possible application could this have?<p>The snapback effect is not limited to uncooked pasta noodles and can be applied to rods of all sorts. The discovery of how to cleanly break them in two could be applied to future engineering projects.</p><p>Likewise, knowing how things fragment and fail is always handy to know when you're trying to build things. Carbon Nanotubes, <a href="https://bigthink.com/ideafeed/carbon-nanotube-space-elevator" target="_self">super strong cylinders often hailed as the building material of the future</a>, are also rods which can be better understood thanks to this odd experiment.</p><p>Sometimes big discoveries can be inspired by silly questions. If it hadn't been for Richard Feynman bending noodles seventy years ago, we wouldn't know what we know now about how energy is dispersed through rods and how to control their fracturing. While not all silly questions will lead to such a significant discovery, they can all help us learn.</p>
A study looks at the performance benefits delivered by asthma drugs when they're taken by athletes who don't have asthma.
- One on hand, the most common health condition among Olympic athletes is asthma. On the other, asthmatic athletes regularly outperform their non-asthmatic counterparts.
- A new study assesses the performance-enhancement effects of asthma medication for non-asthmatics.
- The analysis looks at the effects of both allowed and banned asthma medications.
WADA uncertainty<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzUzNzU0OS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxMDc4NjUwN30.fFTvRR0yJDLtFhaYiixh5Fa7NK1t1T4CzUM0Yh6KYiA/img.jpg?width=980" id="01b1b" class="rm-shortcode" data-rm-shortcode-id="2fd91a47d91e4d5083449b258a2fd63f" data-rm-shortcode-name="rebelmouse-image" alt="urine sample for drug test" />
Image source: joel bubble ben/Shutterstock<p>When inhaled β-agonists first came out just before the 1972 Olympics, they were immediately banned altogether by the WADA as possible doping substances. Over the years, the WADA has reexamined their use and refined the organization's stance, evidence of the thorniness of finding an equitable position regarding their use. As of January 2020, only three β-agonists are allowed — salbutamol, formoterol, and salmeterol —and only in inhaled form. Oral consumption appears to have a greater effect on performance.</p>
The study<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzUzNzU0Ny9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MTIzMDQyMX0.Gk4v-7PCA7NohvJjw12L15p7SumPCY0tLdsSlMrLlGs/img.jpg?width=980" id="d3141" class="rm-shortcode" data-rm-shortcode-id="ebe7b30a315aeffcb4fe739095cf0767" data-rm-shortcode-name="rebelmouse-image" alt="runner at starting position on track" />
Image source: MinDof/Shutterstock<p>Of primary interest to the authors of the study is confirming and measuring the performance improvement to be gained from β-agonists when they're ingested by athletes who don't have asthma.</p><p>The researchers performed a meta-analysis of 34 existing studies documenting 44 randomized trials reporting on 472 participants. The pool of individuals included was broad, encompassing both untrained and elite athletes. In addition, lab tests, as opposed to actual competitions, tracked performance. The authors of the study therefore recommend taking its conclusions with just a grain of salt.</p><p>The effects of both WADA-banned and approved β-agonists were assessed.</p>
Approved β-agonists and non-asthmatic athletes<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzUzNzU1MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxMzkxODk0M30.3RssFwk_tWkHRkEl_tIee02rdq2tLuAePifnngqcIr8/img.jpg?width=980" id="39a99" class="rm-shortcode" data-rm-shortcode-id="b1fe4a580c6d4f8a0fd021d7d6570e2a" data-rm-shortcode-name="rebelmouse-image" alt="vaulter clearing pole" />
Image source: Andrey Yurlov/Shutterstock<p>What the meta-analysis showed is that the currently approved β-agonists didn't significantly improve athletic performance among those without asthma — what very slight benefit they <em>may</em> produce is just enough to prompt the study's authors to write that "it is still uncertain whether approved doses improve anaerobic performance." They note that the tiny effect did increase slightly over multiple weeks of β-agonist intake.</p>
Banned β-agonist and non-asthmatic athletes<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzUzNzU1Mi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNjI3ODU5Mn0.vyoxSE5EYjPGc2ZEbBN8d5F79nSEIiC6TUzTt0ycVqc/img.jpg?width=980" id="de095" class="rm-shortcode" data-rm-shortcode-id="02fdd42dfda8e3665a7b547bb88007ef" data-rm-shortcode-name="rebelmouse-image" alt="swimmer mid stroke" />
Image source: Nejron Photo/Shutterstock<p>The study found that for athletes without asthma, however, the use of currently banned β-agonists did indeed result in enhanced performance. The authors write, "Our meta-analysis shows that β2-agonists improve anaerobic performance by 5%, an improvement that would change the outcome of most athletic competitions."</p><p>That 5 percent is an average: 70-meter sprint performance was improved by 3 percent, while strength performance, MVC (maximal voluntary contraction), was improved by 6 percent.</p><p>The analysis also revealed that different results were produced by different methods of ingestion. The percentages cited above were seen when a β-agonist was ingested orally. The effect was less pronounced when the banned substances were inhaled.</p><p>Given the difference between the results for allowed and banned β-agonists, the study's conclusions suggest that the WADA has it about right, at least in terms of selection of allowable β-agonists, as well as the allowable dosage method.</p>
Takeaway<p>The study, say its authors, "should be of interest to WADA and anyone who is interested in equal opportunities in competitive sports." Its results clearly support vigilance, with the report concluding: "The use of β2-agonists in athletes should be regulated and limited to those with an asthma diagnosis documented with objective tests."</p>
Certain water beetles can escape from frogs after being consumed.
- A Japanese scientist shows that some beetles can wiggle out of frog's butts after being eaten whole.
- The research suggests the beetle can get out in as little as 7 minutes.
- Most of the beetles swallowed in the experiment survived with no complications after being excreted.