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. My parents help me on how to write in both hands . But when the times passed i didn't even notice that i am already left handed. I only notice it when the mother of my classmates used to wait to dismiss told me that i'm not using right hand anymore so i think im just comfortable using with my left hand. And later i realised that the things are in favor on right hands like armchair, kitchen knife, computer mouse and etc. and it makes me uncomfortable.☹️

  2. I am Left handed, my husband too, my sister left handed & her husband, makes it Great when we go out to eat, Our Son is Right handed, he does ALL SPORTS LEFT HANDED. the only thing I do is Bat right handed.

  3. Me: writing
    Girl * walks up to me omg ur left handed I did not know that ,how do u right like that ??!!!

    Edit : lol right like that.

  4. When your left: writing like a human being

    Class: OH MY GOD DOES THAT HURT?

    Me: wtf this is how I write.

  5. 82% : IM A LEFTY!!!!
    17% : ambidextrous and other stuff that RELATES TO THE VIDEO
    1% (aka me) :harry potter is right handed

  6. I've been proposed to 17 times – they were mostly South Paws. My 2 late hi husbands were . The 5 i said yes to were. My son is. Both our cats are & all 5 of my horses were. I was until I broke all 34 bones in it and spent next 4 years in casts at a young age being forced to be righty-still do most things but writing lefty. try "everything lefthanded.UK.com" cameras, wallets, cookware, yard & work tools, learn to tie shoes -hands on how to-, how to teach lefty's how to write for teachers, keyboards, musical instruments, and things with left & right hand set ups. so many things that make life easier for little lefty's to old ones.

  7. i hate being lefty becuz when i play pc games i need to switch the mouse into left 😭 and i can't properly use my right hand it's like a new born baby's hand

  8. I didn't know that I was supposed to born with a dominant hand, I thought my 1st-grade teacher was supposed to tell me to choose

    yeah, I found out this year that I'm ambidextrous…

  9. Right handed:*sees left handed writing

    Right handed: Woah!!! Your left handed?! My my dads ex’s brother’s roommate’s favorite co-workers least favorite co-workers 6th grade English teachers aunts great grandmothers uncles bosses fiancés cousins judo teachers dads right handed

  10. It's not that some people are left handed that's a choice just like being right handed is a choice.
    I use either because I don't believe in dominant right hand nonsense.
    Back in the day "left handed" people were forced to use their right proving anyone can be left or right handed.

  11. I can do anything in both of my hands but of course my left isn't as my right I wrote this comment with left hand it took more time but once I started writing I find it easier

  12. I commonly use right hand

    when I'm writing, drawing, grabbing, hitting, aiming something.

    and I open bottle cap using right hand.

    I use left hand

    when I'm playing billiards, using chopsticks, holding cigarette and so on.

    I use both hand

    when I'm using hammer, screw driver, fly-flap.

    and playing sports(ping pong, tennis, badminton and so on)

    what am I?

  13. I use right when writing but mostly left when doing more practical activities. I use either right or left when playing badminton and sometimes when the toss is incorrect, I use left and I could control my left more accurately than the right

  14. I'm left-handed, and as I once commented on a video listing different things left-handed people struggle with in a right-handed world (follow this link to see that video; https://youtu.be/42NNT0TBCIE)
    "The left side of your brain controls the right side of your body, and vice versa; left-handed people (like myself) are the only ones in their right mind."
    That comment earned positive feedback from other left-handers, and negative feedback from right-handers, for obvious reasons.

  15. The statistics on 2:23 seem to be off –
    20% of 19% is 3.8% of total, so that means 15.2% of all lefties process language on the left side exclusively, 66.2% on the right side exclusively and 3.8% on both sides.
    These sum up to 85.2%, implying that around 15% of lefties do not process language on any side.
    Could anyone please clear that up for me?

  16. Ok so I write with my left do everything else with right.

    Also me and my uncle have the same bday we are both left handed if this normal

  17. me: a right handed person watching this video while brushing my teeth
    realising I’m holding the toothbrush with my left hand
    me: hm

  18. My grandfather once told me a story in which he was burtaly hit with the classic teacher stick for being left handed and was forced to write with his right hand for his whole school life.

  19. Im a righty but i know the struggles of those lefties out there. I just wanna let you know that we all have limitations, you can either run from those limitations, or learn from them. You lefties are still humans that can do everyday tasks. Don’t let the world that think of Left as a sinister sign. No. Left is like Right. So live life to the fullest. Being a lefty is normal. 😁

  20. I think that most right handed people, who had kids who were right handed; Most likely taught their kids to hold a pencil that same way.

  21. I'm righty and will never force my kids to be righty if they are naturally lefty I would actually prefer at least one of kids be lefty

  22. I wrote by left handed.. But because of my mom i have to write by right hand now and work in left hand.. My mom scold me but i can't help but work by my left hand.. I don't know am i lefty or right hand one??

  23. I'm left-handed
    probably I'm mixed handed..
    cuz i write and use scissor with my left hand and almost all the works using right..
    What's the theory behind it

  24. Okay. I write with my right hand but apparently when it comes to musical instruments, I play it with my left hand. When texting using my phone with one hand, I prefer my left hand. Someone please. Waah. I wanna know how my brain works. Hahahuhu. Still can't fully say im ambidextrous since I couldnt really write well with my left hand.

  25. On our country, being a left handed is a taboo, if you raised your son as left handed, he is gay… Idk why tho hahaha. My mother is leftyand i was a girl so she taught me how to write. Now my father hates us because we cant open bottles or cans…. Trust me, when a right hamded person opens a bottle, it was easy for them, but when i try… Oh my… Idk why i cant open RIP..

  26. 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.

  27. 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

  28. 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?

  29. 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 😉

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

  31. I'm left handed but the only thing I do with a left hand is write, I do all the others things with right hand because I have more control of it, but my left hand is definitely stronger

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

  33. 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.

  34. 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.

  35. 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

  36. 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.

  37. 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

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