Why Are Some People Left-Handed?

Why Are Some People Left-Handed?


[MUSIC] [MUSIC] Evolution spent nearly 400 million years crafting
these works of art, two of the most important pieces of the human evolutionary puzzle.
Yet 99% of us end up being good with one hand and not the other, for common tasks like writing,
high-fiving, and the all-important one-handed texting.
Even life itself seems to have chosen sides: our amino acids are said to be “left-handed”,
our DNA turns in a right-handed helix. Both hands seem fully capable, both are connected
to fully functional arms, so we’d expect an even split when it comes to which hand
we prefer. In the animal kingdom, where we find creatures with a preference for one paw,
hoof, or wing, it’s usually 50/50. Yet on average, only 1 out of 10 humans are southpaws.
I guess the real question is “Why are so few people left handed?” Maybe because it’s the world is conspiring
against them… Spiral notebooks. Scissors. E-readers. Video
game controllers. Zippers. Even can openers. If only someone would open a chain of stores
specifically stocked with products for left-handers. That’s a money-maker. Even language hates lefties.
To be correct is to be right… and correct is also word that comes from “right”.
Gods are full of righteousness.To be skillful is to have dexterity. Kings are regal.
Left itself comes from Old English, meaning “weak”. Words for left give us sinister.
Gauche. Maladroit. Bad dancers have two left feet. But language turns out to be an important
part of the puzzle. Our brains are cross-wired, meaning the right
hand is controlled by the left side, and vice versa. But that doesn’t mean our brain’s
symmetrical. In the 1860s, French scientist Paul Broca discovered that a region of our
brains used for speech processing is usually located on one side. Language is a complex
process, and the move to one hemisphere probably helps the brain deal with it more efficiently. Today we know that in 99% of right-handers’
brains, Broca’s area is located only in the left hemisphere. And in left-handers’
brains… it’s also on the left, 70% of the time. Only 19% of lefties process speech
in the right hemisphere, and 20% of them use both. So… language and hands, not directly
linked. That’s… confusing. Two similar theories have been proposed to
explain this. They suggest that as early humans evolved, a gene mutant popped up that threw
a whole BUNCH of of our brain’s functions to one side and allowed them to specialize. If you have two copies of the so-called Right
Shift mutation, language and hand dominance move to the left hemisphere. That shift is
slightly less if you carry one copy, and if you don’t carry the Right Shift mutation
at all, language and handedness could go to the right or left, just by chance. This means instead of their being a gene for
left-handedness, it’s really the lack of a gene. A genetic influence makes sense, since parents
seem to sometimes pass on handedness to their kids. While two right-handed parents only
have a 9% chance of having a left-handed child, one parent being left-handed raises that to
19%, and two to 26%. But research has found evidence of right-hand
preference in captive chimps, and yes, I’m talking about throwing poop. This would mean
that a brain shift for coordination came first, before we became the talking, throwing geniuses
we are today. There’s even another theory, which goes
back to the video we did on how our bodies tell right from left when it comes to our
guts, that this whole brain-hand sidedness can be traced all the way back to our embryonic
days. And in 2013, researchers reported that some of the same genes that tell our spleens
and stomachs which way is which are linked to brain asymmetry. I know you guys hate this, but the answer
is we still don’t really know for sure why more of us aren’t left handed. Sorry. As
you’ve seen we’ve got some great ideas that people are still researching, but that’s
how science works! Of course, if being right-handed and shifting
our speech and coordination to one side was such a great thing for evolution, then why
do lefties still exist? One idea says whether it’s on the baseball
mound, the tennis court, we right-handers do worse when facing lefties. We’re just
not used to all your strange Southpaw ways. If you happen to be holding a sword instead
of a tennis racket, being a lefty might be a great survival tool. A simpler theory is just that nature enjoys
variety. Chris McManus believes that left handers may have what he calls “random cerebral
variation”, their brains are more… shuffled up. This might lead to more unexpected connections,
more cross-talk between the right and left hemispheres, and maybe more creativity. What’s
clear is that having a diverse set of brains have made humans a much more interesting species. We may not have all the answers yet, but these
questions have taught us a lot of important lessons about the brain along the way. And
hey, at least we’re not burning them at the stake. Stay curious. If you want to learn more about southpaw science,
check out the book “A Left Hand Turn Around the World” by David Wolman, link down in the
description.

100 thoughts on “Why Are Some People Left-Handed?

  1. How I type with my left hand: Handwrutubg
    How I type with my right hand: Hsnfrriting
    How I type with both hands: Handwriting
    I frequently write with my left hand tho.

  2. People told me left handed people are smarter and have better hand writing. I’m here, with my crappy handwriting (no kidding, my friend even told me she didn’t like my handwriting) and my horrible grades (my right handed friends always get 100s and I get like b’s and c’s.) I just don’t understand where this whole assumption came from. People say left handed people think the other way as to right handed people, or stuff like that. I mean, they could be silly legends or the coincidental truth that famous celebrities are left handed, but I guess left handed people to me are just left handed .-.

  3. A friend I’ve known for over 6 years just realized I was left handed….I almost threw my hands (no pun intended) …

  4. Im the only one in my family (that is still alive) thats left handed. Both parents are lefties. My living grandma is right handed. And other cousins and etc are all right handed

  5. Who else writes with your left hand but not with your right, uses your right hand for sports and right foot for Soccer and can use scissors and one hand type with either hand?
    Anyone? I’m not ambi as I cannot write with my right hand

  6. "WOOWW You're left-handed??!!" and "That means you're smarter than everyone!!" Are the two most repeated questions I've been asked in my life. I just want to sigh when I hear someone ask me if I'm left-handed. It's not something I think about all the time, it's just the way it is.🤷🏽‍♀️

  7. my eyes are left dominance but my arms and legs swap dominance, I was a very clumsy kid but I've found I'm really good at mapping out a workspace

  8. I think it’s funny when someone says “you’re left handed?!!?”
    But then I really mess em up because I play guitar right handed.

  9. I all comes to the point of efficiency. Mankind focuses on efficiency. So they are making new and innovative tools that can help us with everything. Among them there are tools that require hands. But those tools are not efficient for both hands. Not all the tools that is. Pen can be used by both hands but a can opener is to be used by only right hand. Its inefficient for people to make tools both for right and left. So most of the tools are for right hand use. And as we are used to using these right handed tools we become right handed ourselves. To support my theory I can give an example of playing soccer/football. There are a lot of left footed player. Tell me what you guys think.

  10. I HAVE to be a lefty because I had a stroke in uteral when I was born and the left side of my brain was damaged and that effected my whole right side of my body, so now I have a right hand delay

  11. I used to be right handed until one day my mum was conducting an "experiment". I was only 3 years old and my sister was 4. We were both practicing writing and my mum whispered to me, saying "I heard that lefties are smarter". I was pretty familiar with being right handed up to that point and everything changed within 4 months, I became a lefty. But not "purely" lefty. I write on a book using my left hand but write on the board using my right hand. Throwing and catching things sometimes feels more natural on my right, sometimes on the left. I play instruments (guitar, drums) like how a right handed person does. I use a spoon on my left but scroll my phone with my right hand. I pick things up using my right hand, I inject myself using my right hand but I use a pair of scissors and knives using my left hand.

  12. I'm a lefty and had a very tiny part of the left side of my brain removed because of cancerous cell growth. It took me more than a year to learn how to talk 'straight' again and I still have trouble. Great Video.

  13. I am both left and right handed (Ambidexterity) and it's kinda confusing bc you get people who ask you weird questions and they look at u and stuff. But its actually kind of cool

  14. In older times people thought lefty’s were witches so people would kill lefty’s if they found one

    -a fellow lefty 2019

  15. I don’t get why they make special scissors for left handed people, I can use scissors just fine and I’m left handed. Also I can (somewhat) use a controller.

  16. I write with my left hand but kick with my right foot and throw with my right hand 🤣
    My mum, dad, sister and brother are right handed but I'm left handed 🤔

  17. I wanted to learn how to write with both hands, and I ended up finding this… glad it wasn't a waste of time at least. I'm glad I'm a lefty.

  18. Fun fact: Birds are one of the few animals (besides humans) who display a marked preference in handedness. Over 95% of all birds in the word are left-handed; or I suppose you could say "left-footed" since we're talking about their talons and not wings. Go up to a tame bird and get it to step up on your finger, and it'll almost always use its left foot to do so.

  19. Explain this!I am left handed,at least I write with my left hand,but I prefer playing handball with my right hand because I'm better with it.I move the chess pieces with my left hand and I write ( on my phone ) with my right hand more!I'm also pretty creative and I think logically,I'm also one of the 9% all of my 4 other brothers are right handed.How can this be?Am I a mixture of some kind?

  20. Bad dancers have 2 RIGHT feet
    get rekt old english and old latin and languages that hate on us no hate on the right handers just to the old languages

  21. Humans don’t know sht about the human body, animals and this beautiful planet but little shts are trying to colonize Mars… fk’ing fix the planet that made you

  22. Well im a left handed and its feel like your left hand its too strong and the right hand is too weak for me

    I tried to write in right hand and its torture my right hand . /.
    But other people ask me how i write in left hand well let me say its same at the right hand but a little bit harder in left handed. ./.

  23. Being left handed skips a generation! If you are left handed then a few or one of your grandchildren will be left handed .

  24. I take great joy in asking unsuspecting friends if they would open a can for me, when they find the can opener in the kitchen they mostly stumble on the fact that the "tooth" is twisted the wrong way, usually i tell them to get the other can opener in the next drawer.

  25. I have a saying. "Those who are left-handed are in their right minds."

    Fun fact: I may be left-handed when it comes to writing, but I'm actually ambidextrous. I use my right hand more for several things, like bowling, carrying heavier items and steering my bike. If I try to use my left hand for steering my bike I crash. lol.

  26. To help silence all the 'righty' comments that we get in every day life, wouldn't it be interesting if the one day if the world woke up to a whole week of everything being made,designed,used or ever fitted 'Left Handed'. Having spent the last 62 years left handed I think I'd cope alot better than any right handed person. If only………

  27. The strange thing is, I'm normally right handed, but some things I can do as good or better with my left hand. For expamle badminton.

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