Have you ever wondered what causes people to be born left handed? Why are such a small percentage of society left handed, rather than it being more of a 50/50 mix? This week LeftyFretz has been trying to find out…
Through some exhaustive research (*cough*, an hour on Google!) I found out that no one really understands for sure. Ultimately hand preference comes down to a variety of factors, partly genetic and partly environmental, but there’s no real conclusive evidence with which to give a definitive answer.
Until scientists finally crack this little conundrum we can only hypothesize at best. Here are a few of the theories I found that attempt to explain why people are left handed. Some are a little more far-fetched than others…
Left Handed Genes
Some scientists believe that left handed people simply lack the right-handed gene. This theory has never been conclusively proven and the ‘right handed gene’ has never been located. However, a further group of scientists have claimed to have located a specific gene which when present does show an increase in left-handedness. Unfortunately, possession of this gene also apparently results in an increased chance of psychotic mental illness – great!
Evolutionary Selection
Thomas Carlysle, a 19th century British writer suggested that left handers form such a small percentage of society as a result of some evolutionary weeding out in days gone by. For example, a left handed warrior would hold his shield with his right hand, thereby leaving his heart (which is located more to the left) more exposed. So the higher death rate of lefty warriors would help to justify the highly elevated number of right handed people today.
Prenatal Trauma/Hormonal Imbalances
Some scientists believe that babies who are exposed to traumas within the womb are more likely to exhibit left-handed tendencies. This theory can be backed up by the fact that left handed people are more likely to develop mental illnesses, perhaps as a result of the possible brain damage incurred during the developmental period. In more modern times it has been suggested that ultrasound scanning of the uterus can affect the development of the brain, perhaps leading to an increased chance of left handedness.
Also, studies have shown that whilst in the womb, exposure to incorrect hormonal levels can lead to an increased frequency of left handedness. For example a recent study has shown that exposure to higher than normal levels of estrogen can increase the chances of a baby being a lefty.
Other theories suggest that exposure to high levels of testosterone can impede the development of the left side of the brain, which results in the right side becoming dominant. As you probably know already, left handed people are generally right-brain dominant. This theory supports the idea that there are twice as many left handed males, due to naturally higher levels of testosterone.
Research also shows that older mothers are more likely to produce left handed babies.
Vanishing Twin Theory
The vanishing twins theory suggests that left handed people were originally one half of identical twin foetuses in the mother’s womb. However the right handed foetus fails to develop very early on during the pregnancy and is reabsorbed by the mother’s body. Although twins do have a high occurrence of left/right-handedness in the pair, this theory has been discredited by Australian scientists.
Physical Conditioning
People who injure or lose function of their right hand for an extended period of time can switch to a left-handed predisposition – even after the hand heals. This usually only occurs after a period of eight months or more when the initial change to using the left handed has become the norm for the individual.
Imitation is the Sincerest Form of Flattery
Some younger children may try to imitate older family members or people they look up to, and end up becoming left handed themselves. I wonder just how many 11 year old girls have taken to learning left handed guitar because of Justin Bieber? Believe it or not, I see this on Twitter every single day!
Do you buy any of these theories? I kinda like the dead twin thing myself, that’s some freaky stuff right there! Or perhaps you’ve read another explanation somewhere else. Leave your thoughts in the comments section below.
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Justin Bieber is left-handed?? Shit, he’s a disgrace n insult to lefty guitarists all over..
PS – The gene is called LRTM1 or something right?
On the plus side, he’s creating a small army of lefty guitar players. More players can only be a good thing, regardless of how horrendous their musical tastes are
Almost right with the gene yeah, LRRTM1. More info here if you’re interested http://news.bbc.co.uk/1/hi/6923577.stm I find all this stuff pretty interesting, but I didn’t want to go into too much detail in this post. Too many of the other articles I found on this topic just bombard you with scientific terms and references.
Interesting thing about imitation – I’m as left-handed as they come but one of the few things I do right-handed is catching and throwing because I was copying my right-handed older sister who was trying to teach me to play ball. And it just kinda stuck with me…
I’m the only lefty in the family btw.
this is very interesting stuff, it does make you think, but to complicate things even more , what about us ambidextrous people? i wonder what happend there?…lol…. i do so many things right and left handed, i play guitar left handed but i play drums right handed, the list goes on. its weird stuff……. also finding out justin bieber plays left hand guitar is a shocker but i take comfort in the fact how many of the greatest guitarists ever are/were southpaws…… ie hendrix, paul mcartney, tony iommi, ect
I would guess that there are more right handed people out of necessity of easier survival. Right handed minds, concepts and tools simply dominated the Status Quo. I don’t think there will ever be a single scientific reason why a person will be left handed whether its the LRRTM1 gene or a broken right arm. There are a lot of mental illnesses when it comes to handedness, probably more to do to the overall confusion and stress of changing the way what part of the brain controls certain motor functions, over and over again. Lefties have a different brain symmetry with motor functions, and due to tools being set up for the dominate right hand, its a natural handy cap. There will always be lefties, the number is going up most likely due to cultural acceptance, and the death of the old myths about lefties. However, In the end lefties will most likely advance faster due to more experience with natural handicaps, we have to work harder for every day functions. It’s a division of symmetry that had to happen one way or the other. Men to Women ratios probably work the same way when it comes to dominance.
i’m a lefty – write with my left hand ofcourse… but since everybody else around me are all right handed, i am forced to learn how to play the guitar with my right… the funny thing is, i learned quickly with my right!!! But finding site dedicated for lefties…i think i am going to tinker my acoustic guitar and replace the strings… i’m so gonna learn how to play the guitar with my left this year!!!!
Hey, Just because we lefties have an “increased chance of psychotic mental illness”, can also mean a “increased chance of genius breakthrough”! Keep it left!
from the guy still looking for the elusive “N” note…
I have four children two are left handed……one originally started with his left then went to his right….now he writes right handed but plays soccer left footed and pool 8 ball and golf left handed my older son who is left handed plays eight ball right handed….only one child is truly right handed…..and yes my left handed children are very creative one is music and the other art…….I do find it interesting to read some of these facts especially the vanishing twin…….oh and my first grandchild is also left handed….
That’s so weird!! I actually was both born from an older woman, and.. wait for it.. was going to be a twin, but my twin passed away whole still inutero. So I guess it’s not TOO far-fetched, eh? Oh, I also read somewhere that more serial killers are left-handed.
As far as the ultrasound, that’s not a 100% guarantee. We went for ultrasound scans almost twice a week because of the special condition of my wife during her pregnancy. My son is not a lefty. He doesn’t play guitar (yet…) but he holds his pen or crayon with his right hand.
. Anyway, it just felt right, holding it that way.
My leftyness was found out when I held my pen in my right hand copying my sisters right handed writing. I was mirroring her every move on the paper. When I picked up my dad’s guitar, she said “You’re holding it wrong!” (that sentence was later stolen by Steve Jobs
i learnt how to play right handed guitar because thats just how the guy who taught me, taught me. but i think that we lefties have a advantage when playing right handed, because we should be able to reach the choard positions easier with our left hand being stronger. but i havnt tried the left handed way, so i may be wrong
I’ve read that lefthandness was caused by a lack of oxygen during birth as a defense against damage to the brain
I heard that the universe had enough right hands in the world and wanted to inject genius into her, thus the birth of left handers!
I have always heard the vanishing twin theory. I was also born to an older Mother & the doctor at first told her she thought she was going to have twins but I ended up being a single baby so you never know.
I love the mental illness & serial killer theory lol! Those are funny & not true in my case. I love Simons theory about needing more genius. I think he might be onto something. 
I was talking to my boyfriend , a lefty and he informed me that he works with over 12 left handed people. Only one is female. He is a manager and a leader. He has really motivated people to work together as a team and prospered the business.