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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. Everyone in my family is right handed except for me. Whist being bass ackwards in almost everything, it's taken about 30 years to become better understood by them.

  2. I can write AND type with my both hands. I can snap my fingers with my both hands. And I can even clap my hands with my both hands

  3. I was born using my left hand to write as a Chinese kid but my mom beat me till I used right hand. how can I learn how to write with left hand again?

  4. In dutch: Pas op! Hij is links!
    Litterally: Be careful! He is left!

    But actually… : Be careful! He is Dangerous!

    so, lets fight with swords 😉

  5. Because in an infinite universe infinitely filled with variations of infinite possibilities, it is inevitable that some people will be left handed.

  6. Evolution is a man made concept. It's really just a religion contrary to God and Creation and is easily disproven.

  7. My twin sister is ambidextrous and I do everything left-handed execpt write but that's not the same. I hold my inkpen between my index and middle finger?which I've learnes thru life is unique.

  8. I am a lefty. Both my parents are right handed along with the rest of my family that l know. I have a grandfather that died before l got to know him, but someone who saw his handwriting told me that it looks like he was a lefty too.

  9. Lets try this. Im right handed

    I typed this with my rightvhand only.

    I typed this with my both hand.

    I typrd this with my left handxonly.

    I typed this with my both hand but fast

    I yyped this with my rigjt hand but fa0st

    Urypex tjis eith myclef5 hand bitc fast

  10. The clips you showed of throwing the ball, I FELT that. I swear I turn into an uncoordinated mess when I throw with my left.. humans are weird sometimes.

  11. I can almost write equally with the both hands lol. I’m a lefty but someone got sort of good already as if I were thought as a child but was stubborn to use my right hand

  12. I’ve actually never thought it this way. I always done stuff with both without even realizing it. I write with both hands while I throw better with left and catch better with right.

  13. 99% of the comments are just Lefties acting special, but just because you write with a different hand than everyone else doesn't mean you're better. And if you think I'm just a salty Righty…. No. I'm a pretty chill person, and this is no exception.

  14. I love watching leftys write, I just get a kick out of it n dont look at anything else, I just keep staring, I do let them know too🤗 def lots of stigma is associated, my mom was forced as a child to use her right hand by religious school…. There r no words… long live the LEFT!!! Hand path f*ckers 👌👑

  15. I'm ambidextrous I guess XD I write with my right hand, play lefthanded southpaw on controllers, draw with my right hand but do physical tasks mostly with my left hand. I kind of randomly favour one hand for different activities though. Like I never write with my left hand and I never use right handed controllers. So I don't know if that has a name or my body just picks at random what hand to use with what task and then sticks with it XD

  16. My parents are right handed
    And we are 6 brothers and sisters
    3 are right handed and the other 3 are left handed 🤔🙄

  17. How about this I write and pee with my left hand and that’s it everything else is right hand, golf pool scissors so on… how does that make sense?

  18. Right handed people: here we see a rare species the left handed people

    Me(left handed) here we see somebody who always like everybody else and not special 🙃

  19. Both my parents are right handed but I'm left.
    Myself and my partner are both left handed and our three children are all right handed.

  20. This so weird because where I live there's a lot of lefties. So it's weird reading some comments because some people find it so unlikely. I

  21. Y'all I'm telling you now buying the overpriced 15 dollar scissors is totally worth it. My life changed completely when I was able to cut paper its a whole new world.

  22. Sawing a piece of wood: non-dominant hand is bad at sawing. But also, dominant hand is terrible at stabilizing. With sophisticated tool use, handedness (specialization) is helpful in 2-handed tasks like shooting a bow and arrow or scraping hides. So it’s not just the “good” hand and the “useless” one. (That doesn’t explain why there are lefties, but it should be part of the discussion.)

  23. Left handedness appears to be the last great discovery. The right handed will not want to know the truth about this evolutionary innovation, so it will go on unaddressed.
    Speciation is the answer. Nothing less.

  24. I like your video's but nobody always makes video about is it rare to be lift and right! be aise I'm a RIGHTY but I use my left and right PLS make a video

  25. Okay, weird case with me. I could of swear I was right handed in preschool and ECE. When I was in first grade I learned to use only my left hand. Can anyone else relate?

  26. 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.

  27. 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.

  28. 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.

  29. 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 😂🥊

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

  31. 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.

  32. 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%

  33. 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

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

  35. 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.)

  36. 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

  37. 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.

  38. 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.

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