Why Are Some People Left-Handed?
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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. I'm left-handed and I get annoyed when everyone ask why so few people are left-handed. WHY ISN'T ANYONE ASKING WHY WE HAVE SO MANY RIGHT-HANDERS?! Shouldn't we be asking THAT?! It's basically like only asking why we have a minority and not why something is the majority.

  2. It's funny when people are like, "You're left-handed?" like as if they haven't seen somebody you their left hand as their dominant hand in class. I basically sit there and be like, "My entire family but me and my cousin aren't." before they talk about their relatives. Then before they say anything else, I say, "You know there is, like, 5 other people in my class that are left-handed, right? So, it isn't even that rare." It's worst when it's a classmate.

    By the way, I'm guilty of saying "You're left-handed?" but only whenever I see a 6th left-hander in my class of 40. Like, I see the first four and be like "that's normal" and I find a fifth one and I'm all like, "WHAT? THERE'S MORE OF US?!" and squeal in my head.

  3. I am a leftie but I can write with both hands. I can also use right handed scissors with ease. I have to cover up part of my color pencil drawings to keep from smearing them and getting the pencil lead on the side of my hand. With calligraphy I have to write it backwards so I don't smear the ink. I write sideways to avoid my hand getting poked by spiral notebooks or binders. So in my case I just adapt to the world around me. My parents are right handed and tried to force me to be right handed too but I just refused to do so. I am a leftie and it seems I love challenges.

  4. I loved being a southpaw when I did Thai boxing. People found me so unique, they couldn't cope with it. I felt so special 😂🥊

  5. Had to show this to my religious grandma cause she thought since I was left handed I was the work of the devil hahahaha

  6. Im so confused about my hand.. I can write in my left also in my right hand… Does that exist? … Im so confused that i don't know where im good at? Left or right they r like 50%of left and 50% of right hand.

  7. I'm right handed, but i use my left hand for certain things that i can't do with my right hand, i'm not ambidextrous either since i can't use my hands equally.

    So i read something about cross dominance, which is more rare than ambidextrous, where you use your hands for certain tasks, idk if that is actually a thing.

    Right hand use: 65%
    Left hand use: 35%

  8. At least now we're not forcing left-handed people to do everything right handed the way they did with my grandfather they tied his hand behind his back to force him into writing right handed

  9. Everyone always asks me “How do you write with your left hand??” And I’m all “… cuz I can. How are you RIGHT handed?!”

  10. Proud leftie! Two right handed parents. I think it's an evolutionarily advantage. We are able to best opponents who are right handed as they can't defend as easily. (Swords, spears, punches, etc.)

  11. my parents are right handed and have 6 kids, my oldest brother is left handed, i’m left handed, and we think the newest baby is left handed

  12. I can confirm that there is a conspiracy against left handed people because my grandma was left handed but the teachers at her school would punish her every time they saw her writing with her left hand. Now she can't write with her left hand anymore.

  13. I believe handedness can be trained. An anecdote: my grandpa was born left-handed, but he was born into a culture that looks down on left-handed people. So while he was still a kid, his mom trained him to use his right hand, and now he's ambidextrous.

  14. My mom is right handed and so is my dad and I’m left handed which is really confusing and the only person that my family is aware of that is left handed is my great aunt.

  15. My dad and sister are both lefties, and I lol’ed at the spiral notebook bit. My sister hated those and would always insist on legal sized notepads to write on.

  16. I’m the only left handed in my family
    I’m the only lest handed out of my 11 cousins
    None of my aunts or uncles or grandparents are lefty’s
    So am I like 1% because I don’t think any of my ancestors are left handed

  17. I'm naturally right handed but about 2 & a half years ago I practiced doing 1 handed texting with my LEFT hand when I was sat on the sofa incase I dropped my phone & now I always use my left hand even when I’m walking around but still can handle it just as good with my right hand, I've also started picking up my cup of tea & drinks with my left hand, I originally held my tea spoon in my right hand when I stirred Coffee or Hot Chocolate but after holding my tea spoon in my left hand & a lot of practice I now no longer make a racket when stirring with it in my left hand, one weird thing is I've ALWAYS held my Knife & Fork the left handed way round, I’ve even been practicing writing with my left hand, first I practiced the full alphabet in lower case & capitals & now I’ve began practicing writing sentences in joined up/cursive writing with my left hand & then I started writing the 100 most common words in the English dictionary in joined up/cursive writing it’s got a lot neater & to help this when I use my iPad I hold my iPad in my right hand & use my iPencil with my left hand & when I’m not using my iPencil I hold my iPad in my right hand use the touch screen with my left hand

  18. My parents are both right handed but all 4 of my siblings are lefties and my 2nd sister can use both of her hands

  19. When i write from a pen i use left hand. But in chalkboards i use the right. When I M i use left and all the rest are right. My brains crazy not me.😑

  20. Alot of lefties like to flex on us saying "Haha, you can't write with your left hand", for all those people, try using your right hand 🙂

  21. I feel like everyone saying:

    Like if you’re left hand too! Or

    I’m left handed OR

    This is how many people are left handed
    👇

    ITS SO ANNOYING

    And like 90 percent of the people commenting are lying saying they are left handed. LIKE NO-ONE CARESS

  22. 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.

  23. 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 .-.

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

  25. 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

  26. 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

  27. "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.🤷🏽‍♀️

  28. me: always been a left-hander
    co-worker: wow you're left handed!!!?????
    also me: we've been working together for over a year!

  29. 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

  30. 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.

  31. 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.

  32. 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

  33. 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.

  34. 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.

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