February 24, 2015 • 40 mins
For at least the last 200,000 years, between 10-15% of the human population are left-handed and this fact has utterly left science baffled. In searching to explain handedness, all sorts of contradictory evidence has emerged, creating a fascinating mystery.
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Episode Transcript
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Speaker 1 (00:01):
Welcome to Stuff you Should Know from House Stuff Works
dot com. Hey, I'm welcome to the podcast. I'm Josh
Clark with Charles W Chuck Bryant and Jerry's over there too,
and this is stuff you should know the podcast. Man,
(00:22):
oh man, I would love for people to just lie
on the wall in the studio. Sometimes get squashed. There's
a lot of fun prerecord today. People. I hate that
you miss out on that kind of stuff. But you
know what, that's a that's for us. We we deserve
a little something. Yeah, and that's called pre show fun, fun,
(00:44):
hammering out the details, hammering other details. I thoroughly enjoyed
researching this one. Oh really, it burned my brain a
little bit. It burned my brain a little bit too,
But um, I just I didn't know anything about handedness
and uh no not don't use your hands much. Well,
I mean as far as, uh why you are left
or right handed or ambidextrous. It was all kind of
(01:06):
new information for me. I feel like I had read
that Io nine article, which we should give a huge
shout out because it was forming partially the basis of
this UM episode. Yeah, why are so few people left handed?
From Io nine and they sourced a lot of great
stuff from Discover magazine and their articles, so and science
and science, so it's legit. It is legit. Uh, possibly
(01:30):
even to legit to quit yeah, yeah, which I could
not do with my left hand. I guess I can't.
I just did it. You just did to your science
sign signing to me. I'm equally bad at at doing
too legit to quit finger motions with either hand. I'm
right handed, by the way, what about you, I'm right handed,
(01:52):
but that is weird since you have your mc hammer
pants on. I thought you would be good at that.
That's all just it's not hard to put on pants.
It's hard to do too legit a quit finger motions. Yeah,
I'm right handed. Um to well, I was about to say,
to a fault, but heavily heavily right handed, because after
reading this, I do believe that there is a bit
of a spectrum. I think, um oh yeah, yeah. I think.
(02:15):
I think some people are way dominant with their one hand,
and some people skew more towards you. I can do
some things with this hand, uh, And some people are ambidexterous,
which we'll talk about. Very few, though fewer than you. Think, yeah,
But um, I am heavily, heavily right handed. I cannot
do many uh what's the word I'm looking for? Um? Fine,
(02:38):
not like my fine motor skill tasks. I cannot do
very well with my left hand. I can just like
club things and smack things and knock stuff over, knock
stuff over like Frankenstein clearing a table pretty much. What
about you? And can you do anything with your left hand?
I used to think I was, you know, pretty much
just strictly right handed, But then i've it's especially researching this,
(03:01):
I paid attention, and I'm like, no, I used my
my left hand a little more than I thought. I'm
definitely not ambidextrous. And if there is such a thing
as a dominant hand, it's clearly my right. But this
this article points out, or actually it was a science
m article that said, there's there's this idea that there
isn't a dominant hand, that you have uses for both hands,
(03:22):
and one kind of specializes in one thing and one
specializes in another. And the the example they used to
illustrate that was, um, cutting like meat with a fork
and knife. Yeah, I was gonna ask you about that,
you know, Like I was thinking about I was like, oh, yeah,
I guess I do use the knife pretty well with
my left hand. I thought, crazy, No, my fork is
in my left hand, my knife is in my right hand.
(03:44):
And then I switched the fork over to my right hand.
That's what I did too. I was gonna ask you that.
So I'm definitely right handed, but you know my left
hand does a great job holding the steak in place
with my fork while I cut it with the knife. Yeah. Well,
I'll come to think of it, though, I play guitar
in drums, so I mean I have some left hand skill,
I guess. Um. And I know if you break your
(04:04):
dominant hand, you're gonna learn pretty quickly how to adapt.
So it's possible to learn, uh, if forts to. It's
all very interesting to me. It is, and we should say,
if you happen happen just randomly to be listening to
this episode on August thirteen, Happy National Left Handed Day,
(04:25):
I looked out. When I looked that up, I was like,
I wouldn't it be one of those another stuff you
should know coincidence If this was happened to be released, No,
not even close. Um. And it's good that left handed
people have their own day because they've been fairly maligned
throughout the millennia. Yeah, let's talk about that. Actually, okay,
Um throughout history. In fact, even if you look at
(04:47):
the words uh throughout history, there is a you know,
uh the poopoo left handers. Basically like the word l
y f T left yeah from Anglo Saxon means weak
and the words where the word left comes from and
the word sinister from Latin is the word for left. Yeah.
Anybody who saw that episode of The Simpsons where Ned
(05:09):
Flanders opens the left Toorium knows that because because I
have a sinister reason to invite you all here sinister
meaning left handed man. And that was when he announced
the Leftorium. That show was so smart, you know, very smart.
So many of those jokes like just flew over my
head back in the day, Well, they're coming back to roost. Uh.
(05:31):
There's a long list of um countries who have languages
that link the word right with being good uh and
the left with being bad or wrong uh. And in
some countries even making hand gestures with your left hand
is a no no. Well, and a lot of countries
are a lot of cultures that eat food with their hands.
(05:54):
Then utensils. Um. Using the left hand to eat or
do a lot of things with is considered taboo because
the right it's exactly right. You use the right hand
to eat with, use your left hand to wipe with
right and um, I think if you pay attention and notice,
I'll bet you have a hand that's dominant and that
that um activity wipe in your butt. Yeah, yeah, I'm
(06:16):
alrighty are you? Yeah? Okay? But if you if you
try the other hand, it will feel very weird. Whatever
whatever hand you use normally, it's gonna feel weird if
you use the option, and you'll just send it very messy. Sure.
I wonder if you had a subconscious thing like you know,
I was just eating these candy pecons with my right hand,
and I know I'm gonna go back and eat them
(06:37):
with my right hand. Oh, I don't even use my
hands to eat them. I'm a little too germ conscious.
I scoop food up in the crook of my elbow,
which is very clean because it doesn't come in contact
of other stuff, and then I eat out of the
crook of my elbow. That's pretty funny. Um. So why
have people been I mean, why have they picked on
left handed people. There are some theories that is just
(07:00):
a minority. You know, ten of people are left handed,
and throughout history minorities have been picked on. That's right,
this one thing, Um, there's there's at least a couple
of cultures that equate left handedness with clumsiness. Yeah, that
makes sense to me. Some hypotheses theorized that UM tools
(07:20):
tool making for a very long time, UM has been
done following right handed techniques. Still is in many cases, sure, um.
And so when a lefty was trying to make tools
or do whatever using right handed tools, they would have
been clumsy with them. And therefore the idea that left
handed people were clumsy or weak or whatever could have
(07:42):
developed and carried on. Yeah, like, uh, colonial day, dad
is teaching his two sons. Let's go with the son
and a daughter. Even, let's how to use a saw.
And you know, the son's left handed and he keeps
he can't saw well, so the dad's just like he
favors the daughter because she's you know, she's better with
the saw. It's just it's easy to see how that
(08:03):
could happen. Like he's mad at Roger but pleased with
Prudence because prudence. She's always sawing things. Well, that's a
colonium name, right, Yeah, sure, well I feel like it is. Okay,
well what else is there? Who? Goody? Uh, goody, Alice. Okay,
it's timeless. Um, but there's still that if you're lefty today,
(08:25):
you might be frustrated with things like scissors and can
openers and spiral notebooks and things that sort of U
favor the right handed. Yeah, we're sitting next to a
right handed person at dinner. The elbow thing, it's the worst.
It's because there's so few left handed people. If you're
planning a dinner party, first of all, it's just common
courtesy to know the handedness of all of your guests,
(08:48):
and then to put the appropriately right to put the
left handed person at the end of the table so
that their left hand is their left elbow is off
the table and they don't have to worry about bumping
into other people. Yeah, my mom is left ended, my
father is right handed, and you came out right handed. Yeah, crazy,
I sure did so. Um. Despite everybody knowing that there's
(09:11):
a right handedness and a left handedness, it turns out,
after investigating this kind of thing, science is really baffled
as to what exactly is going on, why we would
have handedness, yeah at all, where it comes from. Why
the proportions seem to be steady. There's a lot of
questions that you know, come up when you look into handedness.
(09:35):
Whereas you know the average person who just kind of
take it for granted, but no, not the average scientists. No, no, no.
There are a lot of interesting theories though. UM. One
is is that, uh, as we all know, we have
a left hemisphere in the right hemisphere of our brain,
and we are one of the only mammals that are
very much UM have a it's called brain lateralization when primarily,
(09:59):
and this isn't a cross the board, but primarily one
hemisphere controls certain things and the other controls other things.
And that is primarily controlling the opposite side of the
body as the hemisphere. UM. But language and um controlling
your you know, fine motor skills like things you do
with your hands and your fingers. I have often been
(10:20):
linked because uh, they are generally on linked together and
on one hemisphere of the brain right for for the
most part, people who are right handed. They make up
the vast majority of human beings by the way. Yeah,
I saw as low as seventy, but nothing lower than that,
you know, eighty didn't Yeah, you're right, sorry, exactly. Um,
(10:43):
those people have their language center in the left hemisphere,
and I guess also their motor cortex in the left hemisphere,
and the know the left and the U. There's a
lot of questions about why this would be when the
brain supposedly is a is always looking for efficiencies as
much as possible. So they're saying, okay, well, these are
(11:05):
two very human activities speech language and using your fingers
to do stuff, right, So, um, they're also some of
the more complex activities that humans engage in. So it
makes sense that you just leave it up to one
side of the brain so that these things can um
not have to cross over the corpus colossum. Yeah, it's
(11:27):
it's just a cluster together. It makes sense. It does
make sense, but it's also a pretty thin explanation. If
you you could also say the other the exact opposite,
that it would make more sense that our motor skills
and our language skills would be in opposite sides of
the brain to give each other a break, rather than
just weighting it down on the same side. The point is, though,
as if you crack open a human brain and you
(11:50):
look for the motor cortex and the language region, the
language center, you're gonna find them most likely, statistically speaking,
on the left hemisphere. Hence more right handedness. Right because
of what you said that um that brain literalization where
stuff that's carried out in the left hemisphere is going
to manifest itself in the right. So if you're shaking
(12:13):
somebody's hand using your right hand, the left hemisphere is
is blowing up. That's right. If you're taking in um
visual information with just your left eye because you got
your right eye closed or it was poked out by
a seagull or whatever, then your right hemisphere is going
to be active, right, that's right. Interestingly, though, if the
opposite isn't true, if you have your language center in
(12:36):
your right hemisphere, it doesn't always mean that you're going
to be left handed. It means you're more likely to.
But um, I like the way this article looked at it.
It's it's an evolutionary rule of thumb. It's not. I
think they said between sixty one and se of lefties
have the language centers on the left. Um over of
(12:58):
right handed people, which raises a really great question, are
is there such a thing as right eas and lefties
or is there such a thing as right ees and
non right ees? Because if there, if the if a
righty and a lefty are equally exactly the same thing,
if handedness is completely um binary like that, then if
(13:19):
you're a lefty, your language center should be on the
right hand side, and that, like you said, that's just
not the case in most lefties even Yeah, that's true,
and uh I O nine article also points out that
it's they don't know why necessarily, but this is just
how we evolved. It could have just been the opposite
right and then we'd have more lefties, right, Yeah, well
(13:41):
that's the idea. But I think, um, there are a
couple of the explanations, possibly of genetic mutations along the
way too, In particular, UH one about two hundred thousand
years ago that basically mutated us to the fact that
we are going to be more right handed in the
in the language center is going to be on the
(14:02):
left hand side. And then more recently, um, there's a
theory that there was a second mutation uh between twenty
thousand and a hundred thousand years ago where that basically
balanced things out, or it canceled that out, which means
the possibility of left handedness became a thing, or else
we would have all been right handed. That makes sense too,
(14:24):
It does make sense and that the humans possibly evolved
to use their hands more, and by using their hands more,
our brains were forced to become specialized and basically forced
to choose. So then some sort of gene was set
up that made the developing human brain most likely to
be a right handed person. Right, And then that second
(14:47):
gene came along and canceled that out in some parts
of the population. I think it's the D gene and
the C gene. Um there are two alleles, which is
the manifestations of a gene at the same location, and
the D gene is more frequent in the population, so
it's more uh promotes the right handed preference. The C
(15:09):
gene is less likely within the gene pool UH. And
so there you have like a fifty fifty chance of
being left handed if you have that C gene. Okay,
I got you, Yeah, But you don't have a being
a left handed person in general. You have about it
only if you yeah, because the D gene is more prominent,
(15:31):
and that means almost certainly you're going to be right handed. Okay,
So the caveat we should add to all of this
is that, um, this is all just strictly conjecture. UM.
And we'll get to a little more of this conjecture
right after this. So, Chuck, we're saying that it's possible
(16:02):
that genetic mutations far back in human history account for this,
and UM, there's a lot of evidence that there have
humans have been mostly right handed for about the last
two hundred thousand years. Fossil evidence suggests this. Looking at
um Neanderthal skeletons, early human skeletons, UM, you can see
(16:23):
evidence on the skeletons of right handedness, and they think
that it's so obvious and obviously prominent because these people
were using things like spears, So if they did have
a hand preference, then a spear would definitely develop that
arm connected to that hand, and it would stay in
the fossil record through the skeletons. Right. They also have
(16:46):
looked at other fossils as far back as one point
six million years. There's a skeleton called, I want to say,
the Kokomo Boy. Even though it's not, but I love
that song. It's the Nario quote, my boy, you love Cocomo.
Sure uh And he is at one point six million
year old Homo air Gaster. And um, they he was
(17:10):
clearly right handed as well. Other fossils have turned up
evidence of right handedness them the teeth. Striations on the
teeth suggest eating with their right hand. So what we
what we can stay with a pretty decent amount of
confidences that at least for the last two hundred thousand years,
humanity has been a majority right handers, and there's been
(17:31):
maybe about this constant ten proportion of left handed people,
which makes the mystery even more crazy to me. Yeah,
but it also makes sense that um an early tool
building and teaching how to use tools, UM, I mean
it holds true today. They've done studies that you know,
you teach your son or daughter to tie a tie,
(17:53):
and it's it's going to be more difficult if they're
left handed and you're right handed for them to try
and do it with their left hand, so or they'll
pick it up easier if they go against their instinct
and learn it how you've talked with. The studies have
shown that so you learn faster from watching somebody and
then using the same hands that they do. Yeah, and
that makes sense. Back in the you know, with Took
(18:15):
took in showing his pal how to use the bone
to smash skull. You know, it's if he picks off
his buddy picks up with his left hand, Took Took's
gonna shake his head. No, no, yeah, use right hand
or they're just gonna you know, they want. Everyone wants
to fit in, even back at in the old days. Well,
that's actually a suggestion of why left handedness is possibly
(18:38):
not a little more prevalent among a certain age group
today because it was equated with being weird or off
or crazy or whatever. Um. And parents and teachers would
force children to learn how to write with their right hand,
effectively wiping out a lot of the left hand to population.
(19:01):
Yeah and um, just jumping back a minute, I wanted
to mention something important that the whole correlation versus causation thing,
um with the whole language center link. Uh, it's not
necessarily that that's a correlation. They appear to be strongly linked,
but no one is saying that because the language hemisphere
(19:22):
is on the left side of your brain that's causing
you to be right handed right there there. And again,
the reason that they are linked in a lot of
scientists minds is that speech and fine motor skills are
basically uniquely human, almost uniquely human. And it's just a
little it's kind of like a red flag or a
(19:42):
signal that they're both usually in the same hemisphere, and
they do seem to be connected. And one hypothesis for
why they're connected I thought was pretty smart. Um the
idea that language spoken language emerged out of gestures hand movements,
which we require fine motor skills, right, but I don't
(20:03):
have trying to do the two legit to quit things.
But the idea that language emerged out of that would
suggest some sort of connection between the two, Like maybe
the fine motor skill section is the more ancient of
the two, and then language evolved out of that. But
we also still need our fine motor skills to like
eat with a fork and knife and everything, so it's
stuck around. It didn't become obsolete just because we started speaking. Yeah,
(20:27):
I like that theory. Um. We we did mention that
this is a largely uniquely human trait um, But they
have followed. Uh, they've basically been looking at our closest
ancestors to try and figure a lot of this stuff out.
Although it did see some studies that said that, like,
cats are left handed because they'll go to swat things
with their left hand. But um, I'm not so sure
(20:49):
about that. Yeah, there's not only is it difficult apparently
to um test or do you attribute handedness to an animal,
it's also difficult to attribute handedness to a person because
the idea of whether or not you're left handed or
right handed, Um, it's still questionable. Like if you write
with your right hand, but you actually can write better
(21:13):
with your left hand or something like that. Right which
what are you? Yeah, is the one you're comfortable with
the one that you're actually better with? Yeah, that's a
good point. Um. But they have been looking at our
our primate ancestors since about the nineteen twenties, and they
have found patterns. Um. Apparently lemurs and are more left handed,
(21:34):
and other prosim uh persimians um, Macaques and old World
monkeys for the most part are evenly split, and gorillas
and chimpanzees are about thirty five lefty. Um, But this
is interesting. The more, as they say here, the more primitive,
the primate, the more likely it is to be a lefty,
(21:55):
which goes in the opposite of the gene mutation. It's
the exact opposite. It implies that we were originally left
handed as primates, and then as we evolved, we became
right handed. So therefore right handed people are more evolved
than left handed people in some weird way. Yeah. So
again it's another inconsistency where and of course this is
(22:17):
in primates too. Um, that doesn't necessarily mean it's the
same thing with humans. No, definitely not. But I mean,
if you're looking at our ancestry and trying to figure
out where handedness came from, you have to go pretty
far back right, And I that's a pretty good example
of how this body of work or knowledge is very contradictory. Still, yeah,
(22:41):
it's baffling, it's pretty awesome. Hey, Chucky, you sent me
something about um ambidextrous nous. Yeah, I thought this is
kind of interesting from mental flaws like, like, it was
just kind of my understanding that anybody who said, oh,
I'm ambidextrous knew what they were talking about. But it
turns out that's really just not the case. For the
most part. It's a very rare um condition. I guess
(23:04):
you'd call it yeah, UM, because I don't know if
there is as a strict definition for what constitutes being ambidextrous.
Like a you know, a switch hitter in baseball doesn't
necessarily mean they're ambidextrous. It means they've taught themselves to
hit from the other side of the plate. Um. If
(23:25):
you notice, as a baseball fan, you're never gonna see
a player that hits uh equally as well on both sides,
Like you know, the great Chipper Jones here from Atlanta,
he favored one side of the plate. Although he was
a switch hitter, he was a much better hitter. I
think it was as a lefty and not as a righty.
So that's not a dextrous now, someone who's taught themselves
(23:47):
because it's a valuable skill in sports to be somewhat
embeddextrous or in a lot of sports. UM. But as far,
I think writing is one of the things that they
can look at um as a clear indicator of which
hand uh you're you're best at, And they say about
only about one percent can write equally as well with
either hand. So that's like super low. Um. Apparently too
(24:12):
So this handedness and this um lateralization of the brain
and division of labor and all that has a lot
to do with how your brain is connected. And apparently
handedness is a part of that too. So like, for example, UM,
people who are ambidextrous UM are more likely to suffer
from schizophrenia, to have schizophrenia. And there it's not just
(24:32):
UM ambidextrous people. Apparently lefties UM show a greater propensity
towards schizophrenia. Something like people with schizophrenia are left handed,
which is a very high proportion considering the general populations,
about ten percent, and UM more than that, dyslexia and
stuttering as well, right, which suggests that left handedness has
(24:56):
an effect on how your brain is wired. It's not
it's too simple, Oh my my hand is I use
my left hand. My my brain is otherwise the exact
same as a right handed person. The brain does appear
to be different in some ways, especially in the ways
that it's connected. Yeah, the um. We we talked about
synesthesia before, one of our favorite Uh what do you
(25:20):
call it? Not a condition? Is it? Yeah? Is it? Sure?
I always just think of condition is something that's uh,
you know, derogatory yeah, like a malady or something. I mean,
I think that falls under that one is one, but
the other one isn't necessarily that one. So like a
malady is a condition, but excerption is necessarily malady. Anyway,
(25:44):
that's my long windway of saying. Synist eats are awesome. Uh.
And the rate of and uh ambidextran synistats is much
higher uh and left handedness than in the general population. Right.
So we have some clues here, like, UM, it's it's
handedness has to do with how your brain is wired,
and if your brain is wired in such a way
(26:04):
that you are left handed, your brain is wired differently
from a person with a right handed brain. Right, And
a lot of studies have backed that up and have
come up with things like it's entirely possible that if
you're a left handed person you've got some advantages in life.
We'll talk about those right after this. So, Chuck, one
(26:40):
of the things that UM left handedness possibly bestows confers
upon you as a benefit is the idea of thinking quicker,
to be able to process information more quickly. Yeah. Uh,
they have done some studies on this. UM did did
a couple of studies. One of which they sat down
on a hundred people, eighty right handers, twenty left handers,
(27:03):
and basically to show them a computer screen with a
single dot either on the left or the right side,
and you had to press a button. It's just a
speed test basically like which side is it on? Left
or right? Right? So something shows up on the left side.
I'm sure you have a clicker in your left hand
and clicker in your right hand. You click the left
hand clicker. But this is all happening very fast, that's right, UM,
and left handed subjects were overall faster. Uh. And the
(27:26):
other tests they had to match up multiple letters that
appeared in some cases on either side of the line
and in other cases on just one side. And again
left handed, Uh, we're faster, but just at matching letters
that were on both sides of the line, which I
thought was interesting well, and that supports this idea that
UM the the brain. The fact that UM, some left
(27:49):
handed people's motor skills and language centers are on different
sides in their brains, UH could make them talk more.
The side of their hemispheres of their brains are more connected.
There's more white tissue where their corpus colossum is more efficient.
It makes sense in a way, but at the same
(28:09):
time you're like, wait, that doesn't make any sense. So
it's kind of this data should be taken and just
locked away in a box until we understand the whole
thing more, because it doesn't really do do a lot
at this point, we don't know enough to make it fit.
And it's actually kind of contradictory to some other stuff
too as far as handedness goes. Yeah, but they do
(28:30):
say that if you're left handed, you may be like
a better gamer or or a pilot because you're able
to just process this quick information super fast, like rapid
fire stuff coming at you. It also suggested to that
language can be processed in both hemispheres among left handed people,
which again would require a lot more connections between the
(28:52):
two hemispheres, faster communication between the two, and hence quicker thinking. Yeah,
and that you in the long run, as you age
and your brain deteriorates, you may be in better shape
as a lefty because your other hemisphere may be able
to pick up that slack more easily, whereas if you're
just a dumb right hander, you're just you know, screwed.
(29:14):
You're in and of course this has approven. This is
just there postulating here, but I mean adds to this mystery. Yeah,
you definitely haven't an advantage in sports in a lot
of cases though. Yes, but not in the way that
you would think. It's not necessarily because your brain is communicating.
The hemispheres are of your brain are communicating. It's more
(29:36):
because your opponent is statistically likelier to be expecting you
to be a right handed person, to have trained against
the right handed person exactly, to be used to playing
a right handed person. Whereas if you're a left handed person,
they're playing you now, you're gonna throw them off guard.
You're gonna catch them off guard, you're gonna be able
to get the drop on them because they're not used
(29:57):
to you, Whereas you, being a lefty, you're still statistically
likelier to have played right handed people, so you know
how to handle them. They don't know how to handle you.
You're the wild card, baby, You win your Rocky. Yeah,
Rocky was left handed. Apparently, Um, and there's a bunch
of sports figures in real life that we're left handed,
(30:18):
and apparently it's one of those things where they're disproportionately
represented as far as successful athletes go compared to the
to the population at large. Yeah, and I think, um,
a lot of times you'll hear about like m M
A or boxing. Um. Tennis is another big one because
if you're used to playing righties most of your life,
that left handed server comes up there and it's it's different,
(30:40):
it's weird, right, and the difference is so pronounced that like,
if you are a pro tennis player or something like that,
or pro boxer, you're gonna train against the lefty before
a match against the lefty. Yeah, you know you're gonna
do what you can to prepare yourself. Yeah. And I
think Robert Lamb wrote this on how staff works are
left handers quicker, um so all better at sports and um.
(31:02):
He also points out that through history, uh, this probably
comes from like soldier training mainly training and fighting and
jousting and sword fighting and everything against other rights as well.
So a lefty would have a left handed warrior might
be more prone to be, you know, the great leader,
like perhaps Alexander the Great right who was supposedly left handed.
(31:24):
What's weird though, is if that had been the case,
if humans have been left handed and right handed, the
proportions have been roughly the same for the last two
hundred thousand years. If you're a left handed combatant, wouldn't
then the proportion of left handed people have grown over
time because of natural selection, because you you have an
(31:45):
advantage in battle or something like that. So therefore the
population of right handed people would drop in relation to
the population of exactly. That makes sense, and I remember,
but that hasn't happened. Yeah, I remember our podcasts on
castles like eighty years ago. Remember they built the staircases
going on the right hand side. Do you remember how mine?
(32:09):
You don't amendingly difficult that was for me to understand. No,
did you have our time with Oh? Yeah, we had
to re record it I think really twice because I
kept getting it wrong. Yeah. We also got in trouble
for for a cussword in that one too. That was
a dark day years ago. Um. Yeah, but the Yeah,
the the castle steps would wind up on the right
(32:30):
side of the wall to give the advantage to the
person higher on the stairs swinging a right handed sword,
because obviously you couldn't swing a right handed sword going
up the stairs because the wall is on your right,
But a left handed combatant advantage taken away even though
you have the higher ground, because all of a sudden
(32:51):
you're cutting the guy's knees off, were cutting them off
at the knees. You know that hurts. It does. But
also include with natural selection. Two is if there were
any real disadvantages to being a left handed person, or
there were advantages to being a right handed person, this
population shouldn't have remained steady over that long of a
(33:12):
period too. I see what you mean. You know, unless
the advantage isn't so great as to you know, cause uh,
that natural selection to occur. You know, maybe, Um, there
are more US presidents that have been left handed, more
MENSU members for whatever that's worth. Half half of the
twelve US presidents so it's World War two have been
(33:34):
left handed. So whereas the normal populations ten to fifteen
percent lefties US presidents of World War two has been
And apparently in campaign all three candidates H. W. Bush, Clinton,
and Pero were left handed. Yeah, that's of the population.
Peroh Man, he was fun to watch, he was Dana
(33:58):
Carvey was fun to watch doing per to Yeah. Uh.
And they say more musicians more or musicians are more
likely to be left handed maybe. Um, and it does
run in families, even though identical twins can have opposite
hand preferences. Oh weird and um there is. In the
nineteen eighties, it was a Harvard neurologist that said that, ah,
(34:21):
lefties are right eas whose brain centers in the womb
change because of high testosterone. Yeah, so there's there's theories
that we become handed in the womb because of something
like that, or birth trauma or some sort of trauma.
While and that. Yeah, it just adjusts the the the
construction of our brains. Um. Supposedly, a mother's age has
(34:46):
an impact on her kids. That's crazy. Statistically, speaking of
a mother, UM over forty who gives birth is has
a higher likelihood of having a lefty kid, way higher,
like hundred cent or something. Yeah, like that's pretty high.
It's more, I don't even know what that means. Yeah,
(35:06):
and then I guess your hand preference emerges about by
seven months, but then it's like set by age three,
So before seven months, you're just flinging poop with both
hands equally as well. Pretty much. I wrote a story
about a guy who found out as an adult that
his mother had suspected he was left handed when he
was a baby, so she immobilized his left hand so
(35:30):
that he would be forced to learn with his right hand.
He didn't seem to take it like that, but he did.
It came across like he felt like something had been
kind of taken from him. He said. It also explained
a lot that he was like so so with stuff
that involved its right hand seemed to be better with
his left. And um that he looked into it, and
(35:50):
that by doing that, which was very popular like kids
were forced to become right handed through the twentieth century.
Um that you are basically making a a less pronounced
copy of the person. You're taking the original and making
like a slightly dimmer effect simile of it, like forcing
(36:13):
their baying to reorganize like that interesting, whereas they thought
they were trying to give them an advantage, to actually
give them a disadvantage exactly. But I would imagine that
if you did that till say age eighteen, and then
all of a sudden started using your dominant hand that
you were naturally born with. It's all like spin ley
in week right. But then once you once you train
(36:34):
it to to to bulk back up, I would imagine
your brain would would be better off like that and
be fuller. So to continue the abuse right until eighteen
dis continued the abuse and then bam, you got a
super kid on your take your little old man Spinley,
hands and fingers like build them back up? And Mr
Show character remember Titanico and they were crossing the hospital.
(37:01):
You know they're getting back together. Yeah, yeah, that's exciting.
So p FT tweeted something some picture is very excited
the whole gang. If you want to know more about
Paul if Tompkins or Handedness or Mr Show or any
of that jazz, you can type that stuff into the
search bar at how stuff works dot com. Since I
said search, part's time for a listener mail. I'm gonna
(37:25):
call this Christian shout out. Hey, guys started listening to
a few months ago, and I've already listened to about
a hundred and sixty episodes. Um and by the way,
we've mentioned this a lot, but if you're just on iTunes,
say and you think, boy, these guys have got three
hundred episodes three one, Yeah, we've got like how many
now seven change yea seven hundred plus that you can
(37:48):
find on our website. Um. Stuff, you should know dot Com. Yeah,
and as a little pro tip, if you go onto
stuff you should know dot com a k the website
with one of the worst searches in the world. Just
do control F and open up your web browsers search
and then type it in and on our podcast archive page.
If you're looking for something, yes, okay, they'll bring it up.
(38:08):
Don't search for it. Don't bother searching for it using
our search tool. Are we working on that? I hope so,
because this is really bad, like it doesn't bring up
anything really yeah, wow, that's pretty bad. Otherwise it even there,
I don't know. I guess for looks lane. Um. So,
getting back to this, we do have a lot of
(38:29):
podcasts out there, for those of you who don't know,
we have seven hundred plus we're talking about. He's uh,
he listened to a hundred and sixty episodes. His favorite
thing about them is how you don't poop poo anybody's beliefs.
I'm a Christian, So when I was very much so
begrudgingly uh listen to your evolution suite. I was expecting
to be mad, but to my surprise, I heard a
(38:52):
very non bias view of evolution. Um I do believe
in evolution, but it's a long story. By the way,
after many years of hearing creation a slam uh people
talk about evolution is a very pleasant surprise. So I
just want to say thanks for putting your hearts but
not your opinions into that episode. That is from Matt
very sincerely, and uh, we've been taking a task here
and there. We try to do our best, matt um,
(39:14):
to keep things on the level like that, but we
are human and we do uh flounder here and there
with that, but we we try, and we appreciate your
kudos for that. Yeah, thanks man. Yeah, if you want
to give us kudos, we would love to hear about that.
Or if you have any great stories that has to
do with handedness, let us know if you had your
arm tied to your waist till you're eight as a baby. Yeah. Uh.
(39:37):
You can tweet to us at s Y s K podcast.
You can join us on Facebook dot com, slash stuff
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Stuff Podcast at how Stuff Works dot com and has
always joined us at our home on the web, Stuff
you Should Know dot com for more on this and
(39:57):
thousands of other topics. Does it how stuff works. Dot
com
Welcome to Stuff you Should Know from House Stuff Works
dot com. Hey, I'm welcome to the podcast. I'm Josh
Clark with Charles W Chuck Bryant and Jerry's over there too,
and this is stuff you should know the podcast. Man,
(00:22):
oh man, I would love for people to just lie
on the wall in the studio. Sometimes get squashed. There's
a lot of fun prerecord today. People. I hate that
you miss out on that kind of stuff. But you
know what, that's a that's for us. We we deserve
a little something. Yeah, and that's called pre show fun, fun,
(00:44):
hammering out the details, hammering other details. I thoroughly enjoyed
researching this one. Oh really, it burned my brain a
little bit. It burned my brain a little bit too,
But um, I just I didn't know anything about handedness
and uh no not don't use your hands much. Well,
I mean as far as, uh why you are left
or right handed or ambidextrous. It was all kind of
(01:06):
new information for me. I feel like I had read
that Io nine article, which we should give a huge
shout out because it was forming partially the basis of
this UM episode. Yeah, why are so few people left handed?
From Io nine and they sourced a lot of great
stuff from Discover magazine and their articles, so and science
and science, so it's legit. It is legit. Uh, possibly
(01:30):
even to legit to quit yeah, yeah, which I could
not do with my left hand. I guess I can't.
I just did it. You just did to your science
sign signing to me. I'm equally bad at at doing
too legit to quit finger motions with either hand. I'm
right handed, by the way, what about you, I'm right handed,
(01:52):
but that is weird since you have your mc hammer
pants on. I thought you would be good at that.
That's all just it's not hard to put on pants.
It's hard to do too legit a quit finger motions. Yeah,
I'm right handed. Um to well, I was about to say,
to a fault, but heavily heavily right handed, because after
reading this, I do believe that there is a bit
of a spectrum. I think, um oh yeah, yeah. I think.
(02:15):
I think some people are way dominant with their one hand,
and some people skew more towards you. I can do
some things with this hand, uh, And some people are ambidexterous,
which we'll talk about. Very few, though fewer than you. Think, yeah,
But um, I am heavily, heavily right handed. I cannot
do many uh what's the word I'm looking for? Um? Fine,
(02:38):
not like my fine motor skill tasks. I cannot do
very well with my left hand. I can just like
club things and smack things and knock stuff over, knock
stuff over like Frankenstein clearing a table pretty much. What
about you? And can you do anything with your left hand?
I used to think I was, you know, pretty much
just strictly right handed, But then i've it's especially researching this,
(03:01):
I paid attention, and I'm like, no, I used my
my left hand a little more than I thought. I'm
definitely not ambidextrous. And if there is such a thing
as a dominant hand, it's clearly my right. But this
this article points out, or actually it was a science
m article that said, there's there's this idea that there
isn't a dominant hand, that you have uses for both hands,
(03:22):
and one kind of specializes in one thing and one
specializes in another. And the the example they used to
illustrate that was, um, cutting like meat with a fork
and knife. Yeah, I was gonna ask you about that,
you know, Like I was thinking about I was like, oh, yeah,
I guess I do use the knife pretty well with
my left hand. I thought, crazy, No, my fork is
in my left hand, my knife is in my right hand.
(03:44):
And then I switched the fork over to my right hand.
That's what I did too. I was gonna ask you that.
So I'm definitely right handed, but you know my left
hand does a great job holding the steak in place
with my fork while I cut it with the knife. Yeah. Well,
I'll come to think of it, though, I play guitar
in drums, so I mean I have some left hand skill,
I guess. Um. And I know if you break your
(04:04):
dominant hand, you're gonna learn pretty quickly how to adapt.
So it's possible to learn, uh, if forts to. It's
all very interesting to me. It is, and we should say,
if you happen happen just randomly to be listening to
this episode on August thirteen, Happy National Left Handed Day,
(04:25):
I looked out. When I looked that up, I was like,
I wouldn't it be one of those another stuff you
should know coincidence If this was happened to be released, No,
not even close. Um. And it's good that left handed
people have their own day because they've been fairly maligned
throughout the millennia. Yeah, let's talk about that. Actually, okay,
Um throughout history. In fact, even if you look at
(04:47):
the words uh throughout history, there is a you know,
uh the poopoo left handers. Basically like the word l
y f T left yeah from Anglo Saxon means weak
and the words where the word left comes from and
the word sinister from Latin is the word for left. Yeah.
Anybody who saw that episode of The Simpsons where Ned
(05:09):
Flanders opens the left Toorium knows that because because I
have a sinister reason to invite you all here sinister
meaning left handed man. And that was when he announced
the Leftorium. That show was so smart, you know, very smart.
So many of those jokes like just flew over my
head back in the day, Well, they're coming back to roost. Uh.
(05:31):
There's a long list of um countries who have languages
that link the word right with being good uh and
the left with being bad or wrong uh. And in
some countries even making hand gestures with your left hand
is a no no. Well, and a lot of countries
are a lot of cultures that eat food with their hands.
(05:54):
Then utensils. Um. Using the left hand to eat or
do a lot of things with is considered taboo because
the right it's exactly right. You use the right hand
to eat with, use your left hand to wipe with
right and um, I think if you pay attention and notice,
I'll bet you have a hand that's dominant and that
that um activity wipe in your butt. Yeah, yeah, I'm
(06:16):
alrighty are you? Yeah? Okay? But if you if you
try the other hand, it will feel very weird. Whatever
whatever hand you use normally, it's gonna feel weird if
you use the option, and you'll just send it very messy. Sure.
I wonder if you had a subconscious thing like you know,
I was just eating these candy pecons with my right hand,
and I know I'm gonna go back and eat them
(06:37):
with my right hand. Oh, I don't even use my
hands to eat them. I'm a little too germ conscious.
I scoop food up in the crook of my elbow,
which is very clean because it doesn't come in contact
of other stuff, and then I eat out of the
crook of my elbow. That's pretty funny. Um. So why
have people been I mean, why have they picked on
left handed people. There are some theories that is just
(07:00):
a minority. You know, ten of people are left handed,
and throughout history minorities have been picked on. That's right,
this one thing, Um, there's there's at least a couple
of cultures that equate left handedness with clumsiness. Yeah, that
makes sense to me. Some hypotheses theorized that UM tools
(07:20):
tool making for a very long time, UM has been
done following right handed techniques. Still is in many cases, sure, um.
And so when a lefty was trying to make tools
or do whatever using right handed tools, they would have
been clumsy with them. And therefore the idea that left
handed people were clumsy or weak or whatever could have
(07:42):
developed and carried on. Yeah, like, uh, colonial day, dad
is teaching his two sons. Let's go with the son
and a daughter. Even, let's how to use a saw.
And you know, the son's left handed and he keeps
he can't saw well, so the dad's just like he
favors the daughter because she's you know, she's better with
the saw. It's just it's easy to see how that
(08:03):
could happen. Like he's mad at Roger but pleased with
Prudence because prudence. She's always sawing things. Well, that's a
colonium name, right, Yeah, sure, well I feel like it is. Okay,
well what else is there? Who? Goody? Uh, goody, Alice. Okay,
it's timeless. Um, but there's still that if you're lefty today,
(08:25):
you might be frustrated with things like scissors and can
openers and spiral notebooks and things that sort of U
favor the right handed. Yeah, we're sitting next to a
right handed person at dinner. The elbow thing, it's the worst.
It's because there's so few left handed people. If you're
planning a dinner party, first of all, it's just common
courtesy to know the handedness of all of your guests,
(08:48):
and then to put the appropriately right to put the
left handed person at the end of the table so
that their left hand is their left elbow is off
the table and they don't have to worry about bumping
into other people. Yeah, my mom is left ended, my
father is right handed, and you came out right handed. Yeah, crazy,
I sure did so. Um. Despite everybody knowing that there's
(09:11):
a right handedness and a left handedness, it turns out,
after investigating this kind of thing, science is really baffled
as to what exactly is going on, why we would
have handedness, yeah at all, where it comes from. Why
the proportions seem to be steady. There's a lot of
questions that you know, come up when you look into handedness.
(09:35):
Whereas you know the average person who just kind of
take it for granted, but no, not the average scientists. No, no, no.
There are a lot of interesting theories though. UM. One
is is that, uh, as we all know, we have
a left hemisphere in the right hemisphere of our brain,
and we are one of the only mammals that are
very much UM have a it's called brain lateralization when primarily,
(09:59):
and this isn't a cross the board, but primarily one
hemisphere controls certain things and the other controls other things.
And that is primarily controlling the opposite side of the
body as the hemisphere. UM. But language and um controlling
your you know, fine motor skills like things you do
with your hands and your fingers. I have often been
(10:20):
linked because uh, they are generally on linked together and
on one hemisphere of the brain right for for the
most part, people who are right handed. They make up
the vast majority of human beings by the way. Yeah,
I saw as low as seventy, but nothing lower than that,
you know, eighty didn't Yeah, you're right, sorry, exactly. Um,
(10:43):
those people have their language center in the left hemisphere,
and I guess also their motor cortex in the left hemisphere,
and the know the left and the U. There's a
lot of questions about why this would be when the
brain supposedly is a is always looking for efficiencies as
much as possible. So they're saying, okay, well, these are
(11:05):
two very human activities speech language and using your fingers
to do stuff, right, So, um, they're also some of
the more complex activities that humans engage in. So it
makes sense that you just leave it up to one
side of the brain so that these things can um
not have to cross over the corpus colossum. Yeah, it's
(11:27):
it's just a cluster together. It makes sense. It does
make sense, but it's also a pretty thin explanation. If
you you could also say the other the exact opposite,
that it would make more sense that our motor skills
and our language skills would be in opposite sides of
the brain to give each other a break, rather than
just weighting it down on the same side. The point is, though,
as if you crack open a human brain and you
(11:50):
look for the motor cortex and the language region, the
language center, you're gonna find them most likely, statistically speaking,
on the left hemisphere. Hence more right handedness. Right because
of what you said that um that brain literalization where
stuff that's carried out in the left hemisphere is going
to manifest itself in the right. So if you're shaking
(12:13):
somebody's hand using your right hand, the left hemisphere is
is blowing up. That's right. If you're taking in um
visual information with just your left eye because you got
your right eye closed or it was poked out by
a seagull or whatever, then your right hemisphere is going
to be active, right, that's right. Interestingly, though, if the
opposite isn't true, if you have your language center in
(12:36):
your right hemisphere, it doesn't always mean that you're going
to be left handed. It means you're more likely to.
But um, I like the way this article looked at it.
It's it's an evolutionary rule of thumb. It's not. I
think they said between sixty one and se of lefties
have the language centers on the left. Um over of
(12:58):
right handed people, which raises a really great question, are
is there such a thing as right eas and lefties
or is there such a thing as right ees and
non right ees? Because if there, if the if a
righty and a lefty are equally exactly the same thing,
if handedness is completely um binary like that, then if
(13:19):
you're a lefty, your language center should be on the
right hand side, and that, like you said, that's just
not the case in most lefties even Yeah, that's true,
and uh I O nine article also points out that
it's they don't know why necessarily, but this is just
how we evolved. It could have just been the opposite
right and then we'd have more lefties, right, Yeah, well
(13:41):
that's the idea. But I think, um, there are a
couple of the explanations, possibly of genetic mutations along the
way too, In particular, UH one about two hundred thousand
years ago that basically mutated us to the fact that
we are going to be more right handed in the
in the language center is going to be on the
(14:02):
left hand side. And then more recently, um, there's a
theory that there was a second mutation uh between twenty
thousand and a hundred thousand years ago where that basically
balanced things out, or it canceled that out, which means
the possibility of left handedness became a thing, or else
we would have all been right handed. That makes sense too,
(14:24):
It does make sense and that the humans possibly evolved
to use their hands more, and by using their hands more,
our brains were forced to become specialized and basically forced
to choose. So then some sort of gene was set
up that made the developing human brain most likely to
be a right handed person. Right, And then that second
(14:47):
gene came along and canceled that out in some parts
of the population. I think it's the D gene and
the C gene. Um there are two alleles, which is
the manifestations of a gene at the same location, and
the D gene is more frequent in the population, so
it's more uh promotes the right handed preference. The C
(15:09):
gene is less likely within the gene pool UH. And
so there you have like a fifty fifty chance of
being left handed if you have that C gene. Okay,
I got you, Yeah, But you don't have a being
a left handed person in general. You have about it
only if you yeah, because the D gene is more prominent,
(15:31):
and that means almost certainly you're going to be right handed. Okay,
So the caveat we should add to all of this
is that, um, this is all just strictly conjecture. UM.
And we'll get to a little more of this conjecture
right after this. So, Chuck, we're saying that it's possible
(16:02):
that genetic mutations far back in human history account for this,
and UM, there's a lot of evidence that there have
humans have been mostly right handed for about the last
two hundred thousand years. Fossil evidence suggests this. Looking at
um Neanderthal skeletons, early human skeletons, UM, you can see
(16:23):
evidence on the skeletons of right handedness, and they think
that it's so obvious and obviously prominent because these people
were using things like spears, So if they did have
a hand preference, then a spear would definitely develop that
arm connected to that hand, and it would stay in
the fossil record through the skeletons. Right. They also have
(16:46):
looked at other fossils as far back as one point
six million years. There's a skeleton called, I want to say,
the Kokomo Boy. Even though it's not, but I love
that song. It's the Nario quote, my boy, you love Cocomo.
Sure uh And he is at one point six million
year old Homo air Gaster. And um, they he was
(17:10):
clearly right handed as well. Other fossils have turned up
evidence of right handedness them the teeth. Striations on the
teeth suggest eating with their right hand. So what we
what we can stay with a pretty decent amount of
confidences that at least for the last two hundred thousand years,
humanity has been a majority right handers, and there's been
(17:31):
maybe about this constant ten proportion of left handed people,
which makes the mystery even more crazy to me. Yeah,
but it also makes sense that um an early tool
building and teaching how to use tools, UM, I mean
it holds true today. They've done studies that you know,
you teach your son or daughter to tie a tie,
(17:53):
and it's it's going to be more difficult if they're
left handed and you're right handed for them to try
and do it with their left hand, so or they'll
pick it up easier if they go against their instinct
and learn it how you've talked with. The studies have
shown that so you learn faster from watching somebody and
then using the same hands that they do. Yeah, and
that makes sense. Back in the you know, with Took
(18:15):
took in showing his pal how to use the bone
to smash skull. You know, it's if he picks off
his buddy picks up with his left hand, Took Took's
gonna shake his head. No, no, yeah, use right hand
or they're just gonna you know, they want. Everyone wants
to fit in, even back at in the old days. Well,
that's actually a suggestion of why left handedness is possibly
(18:38):
not a little more prevalent among a certain age group
today because it was equated with being weird or off
or crazy or whatever. Um. And parents and teachers would
force children to learn how to write with their right hand,
effectively wiping out a lot of the left hand to population.
(19:01):
Yeah and um, just jumping back a minute, I wanted
to mention something important that the whole correlation versus causation thing,
um with the whole language center link. Uh, it's not
necessarily that that's a correlation. They appear to be strongly linked,
but no one is saying that because the language hemisphere
(19:22):
is on the left side of your brain that's causing
you to be right handed right there there. And again,
the reason that they are linked in a lot of
scientists minds is that speech and fine motor skills are
basically uniquely human, almost uniquely human. And it's just a
little it's kind of like a red flag or a
(19:42):
signal that they're both usually in the same hemisphere, and
they do seem to be connected. And one hypothesis for
why they're connected I thought was pretty smart. Um the
idea that language spoken language emerged out of gestures hand movements,
which we require fine motor skills, right, but I don't
(20:03):
have trying to do the two legit to quit things.
But the idea that language emerged out of that would
suggest some sort of connection between the two, Like maybe
the fine motor skill section is the more ancient of
the two, and then language evolved out of that. But
we also still need our fine motor skills to like
eat with a fork and knife and everything, so it's
stuck around. It didn't become obsolete just because we started speaking. Yeah,
(20:27):
I like that theory. Um. We we did mention that
this is a largely uniquely human trait um, But they
have followed. Uh, they've basically been looking at our closest
ancestors to try and figure a lot of this stuff out.
Although it did see some studies that said that, like,
cats are left handed because they'll go to swat things
with their left hand. But um, I'm not so sure
(20:49):
about that. Yeah, there's not only is it difficult apparently
to um test or do you attribute handedness to an animal,
it's also difficult to attribute handedness to a person because
the idea of whether or not you're left handed or
right handed, Um, it's still questionable. Like if you write
with your right hand, but you actually can write better
(21:13):
with your left hand or something like that. Right which
what are you? Yeah, is the one you're comfortable with
the one that you're actually better with? Yeah, that's a
good point. Um. But they have been looking at our
our primate ancestors since about the nineteen twenties, and they
have found patterns. Um. Apparently lemurs and are more left handed,
(21:34):
and other prosim uh persimians um, Macaques and old World
monkeys for the most part are evenly split, and gorillas
and chimpanzees are about thirty five lefty. Um, But this
is interesting. The more, as they say here, the more primitive,
the primate, the more likely it is to be a lefty,
(21:55):
which goes in the opposite of the gene mutation. It's
the exact opposite. It implies that we were originally left
handed as primates, and then as we evolved, we became
right handed. So therefore right handed people are more evolved
than left handed people in some weird way. Yeah. So
again it's another inconsistency where and of course this is
(22:17):
in primates too. Um, that doesn't necessarily mean it's the
same thing with humans. No, definitely not. But I mean,
if you're looking at our ancestry and trying to figure
out where handedness came from, you have to go pretty
far back right, And I that's a pretty good example
of how this body of work or knowledge is very contradictory. Still, yeah,
(22:41):
it's baffling, it's pretty awesome. Hey, Chucky, you sent me
something about um ambidextrous nous. Yeah, I thought this is
kind of interesting from mental flaws like, like, it was
just kind of my understanding that anybody who said, oh,
I'm ambidextrous knew what they were talking about. But it
turns out that's really just not the case. For the
most part. It's a very rare um condition. I guess
(23:04):
you'd call it yeah, UM, because I don't know if
there is as a strict definition for what constitutes being ambidextrous.
Like a you know, a switch hitter in baseball doesn't
necessarily mean they're ambidextrous. It means they've taught themselves to
hit from the other side of the plate. Um. If
(23:25):
you notice, as a baseball fan, you're never gonna see
a player that hits uh equally as well on both sides,
Like you know, the great Chipper Jones here from Atlanta,
he favored one side of the plate. Although he was
a switch hitter, he was a much better hitter. I
think it was as a lefty and not as a righty.
So that's not a dextrous now, someone who's taught themselves
(23:47):
because it's a valuable skill in sports to be somewhat
embeddextrous or in a lot of sports. UM. But as far,
I think writing is one of the things that they
can look at um as a clear indicator of which
hand uh you're you're best at, And they say about
only about one percent can write equally as well with
either hand. So that's like super low. Um. Apparently too
(24:12):
So this handedness and this um lateralization of the brain
and division of labor and all that has a lot
to do with how your brain is connected. And apparently
handedness is a part of that too. So like, for example, UM,
people who are ambidextrous UM are more likely to suffer
from schizophrenia, to have schizophrenia. And there it's not just
(24:32):
UM ambidextrous people. Apparently lefties UM show a greater propensity
towards schizophrenia. Something like people with schizophrenia are left handed,
which is a very high proportion considering the general populations,
about ten percent, and UM more than that, dyslexia and
stuttering as well, right, which suggests that left handedness has
(24:56):
an effect on how your brain is wired. It's not
it's too simple, Oh my my hand is I use
my left hand. My my brain is otherwise the exact
same as a right handed person. The brain does appear
to be different in some ways, especially in the ways
that it's connected. Yeah, the um. We we talked about
synesthesia before, one of our favorite Uh what do you
(25:20):
call it? Not a condition? Is it? Yeah? Is it? Sure?
I always just think of condition is something that's uh,
you know, derogatory yeah, like a malady or something. I mean,
I think that falls under that one is one, but
the other one isn't necessarily that one. So like a
malady is a condition, but excerption is necessarily malady. Anyway,
(25:44):
that's my long windway of saying. Synist eats are awesome. Uh.
And the rate of and uh ambidextran synistats is much
higher uh and left handedness than in the general population. Right.
So we have some clues here, like, UM, it's it's
handedness has to do with how your brain is wired,
and if your brain is wired in such a way
(26:04):
that you are left handed, your brain is wired differently
from a person with a right handed brain. Right, And
a lot of studies have backed that up and have
come up with things like it's entirely possible that if
you're a left handed person you've got some advantages in life.
We'll talk about those right after this. So, Chuck, one
(26:40):
of the things that UM left handedness possibly bestows confers
upon you as a benefit is the idea of thinking quicker,
to be able to process information more quickly. Yeah. Uh,
they have done some studies on this. UM did did
a couple of studies. One of which they sat down
on a hundred people, eighty right handers, twenty left handers,
(27:03):
and basically to show them a computer screen with a
single dot either on the left or the right side,
and you had to press a button. It's just a
speed test basically like which side is it on? Left
or right? Right? So something shows up on the left side.
I'm sure you have a clicker in your left hand
and clicker in your right hand. You click the left
hand clicker. But this is all happening very fast, that's right, UM,
and left handed subjects were overall faster. Uh. And the
(27:26):
other tests they had to match up multiple letters that
appeared in some cases on either side of the line
and in other cases on just one side. And again
left handed, Uh, we're faster, but just at matching letters
that were on both sides of the line, which I
thought was interesting well, and that supports this idea that
UM the the brain. The fact that UM, some left
(27:49):
handed people's motor skills and language centers are on different
sides in their brains, UH could make them talk more.
The side of their hemispheres of their brains are more connected.
There's more white tissue where their corpus colossum is more efficient.
It makes sense in a way, but at the same
(28:09):
time you're like, wait, that doesn't make any sense. So
it's kind of this data should be taken and just
locked away in a box until we understand the whole
thing more, because it doesn't really do do a lot
at this point, we don't know enough to make it fit.
And it's actually kind of contradictory to some other stuff
too as far as handedness goes. Yeah, but they do
(28:30):
say that if you're left handed, you may be like
a better gamer or or a pilot because you're able
to just process this quick information super fast, like rapid
fire stuff coming at you. It also suggested to that
language can be processed in both hemispheres among left handed people,
which again would require a lot more connections between the
(28:52):
two hemispheres, faster communication between the two, and hence quicker thinking. Yeah,
and that you in the long run, as you age
and your brain deteriorates, you may be in better shape
as a lefty because your other hemisphere may be able
to pick up that slack more easily, whereas if you're
just a dumb right hander, you're just you know, screwed.
(29:14):
You're in and of course this has approven. This is
just there postulating here, but I mean adds to this mystery. Yeah,
you definitely haven't an advantage in sports in a lot
of cases though. Yes, but not in the way that
you would think. It's not necessarily because your brain is communicating.
The hemispheres are of your brain are communicating. It's more
(29:36):
because your opponent is statistically likelier to be expecting you
to be a right handed person, to have trained against
the right handed person exactly, to be used to playing
a right handed person. Whereas if you're a left handed person,
they're playing you now, you're gonna throw them off guard.
You're gonna catch them off guard, you're gonna be able
to get the drop on them because they're not used
(29:57):
to you, Whereas you, being a lefty, you're still statistically
likelier to have played right handed people, so you know
how to handle them. They don't know how to handle you.
You're the wild card, baby, You win your Rocky. Yeah,
Rocky was left handed. Apparently, Um, and there's a bunch
of sports figures in real life that we're left handed,
(30:18):
and apparently it's one of those things where they're disproportionately
represented as far as successful athletes go compared to the
to the population at large. Yeah, and I think, um,
a lot of times you'll hear about like m M
A or boxing. Um. Tennis is another big one because
if you're used to playing righties most of your life,
that left handed server comes up there and it's it's different,
(30:40):
it's weird, right, and the difference is so pronounced that like,
if you are a pro tennis player or something like that,
or pro boxer, you're gonna train against the lefty before
a match against the lefty. Yeah, you know you're gonna
do what you can to prepare yourself. Yeah. And I
think Robert Lamb wrote this on how staff works are
left handers quicker, um so all better at sports and um.
(31:02):
He also points out that through history, uh, this probably
comes from like soldier training mainly training and fighting and
jousting and sword fighting and everything against other rights as well.
So a lefty would have a left handed warrior might
be more prone to be, you know, the great leader,
like perhaps Alexander the Great right who was supposedly left handed.
(31:24):
What's weird though, is if that had been the case,
if humans have been left handed and right handed, the
proportions have been roughly the same for the last two
hundred thousand years. If you're a left handed combatant, wouldn't
then the proportion of left handed people have grown over
time because of natural selection, because you you have an
(31:45):
advantage in battle or something like that. So therefore the
population of right handed people would drop in relation to
the population of exactly. That makes sense, and I remember,
but that hasn't happened. Yeah, I remember our podcasts on
castles like eighty years ago. Remember they built the staircases
going on the right hand side. Do you remember how mine?
(32:09):
You don't amendingly difficult that was for me to understand. No,
did you have our time with Oh? Yeah, we had
to re record it I think really twice because I
kept getting it wrong. Yeah. We also got in trouble
for for a cussword in that one too. That was
a dark day years ago. Um. Yeah, but the Yeah,
the the castle steps would wind up on the right
(32:30):
side of the wall to give the advantage to the
person higher on the stairs swinging a right handed sword,
because obviously you couldn't swing a right handed sword going
up the stairs because the wall is on your right,
But a left handed combatant advantage taken away even though
you have the higher ground, because all of a sudden
(32:51):
you're cutting the guy's knees off, were cutting them off
at the knees. You know that hurts. It does. But
also include with natural selection. Two is if there were
any real disadvantages to being a left handed person, or
there were advantages to being a right handed person, this
population shouldn't have remained steady over that long of a
(33:12):
period too. I see what you mean. You know, unless
the advantage isn't so great as to you know, cause uh,
that natural selection to occur. You know, maybe, Um, there
are more US presidents that have been left handed, more
MENSU members for whatever that's worth. Half half of the
twelve US presidents so it's World War two have been
(33:34):
left handed. So whereas the normal populations ten to fifteen
percent lefties US presidents of World War two has been
And apparently in campaign all three candidates H. W. Bush, Clinton,
and Pero were left handed. Yeah, that's of the population.
Peroh Man, he was fun to watch, he was Dana
(33:58):
Carvey was fun to watch doing per to Yeah. Uh.
And they say more musicians more or musicians are more
likely to be left handed maybe. Um, and it does
run in families, even though identical twins can have opposite
hand preferences. Oh weird and um there is. In the
nineteen eighties, it was a Harvard neurologist that said that, ah,
(34:21):
lefties are right eas whose brain centers in the womb
change because of high testosterone. Yeah, so there's there's theories
that we become handed in the womb because of something
like that, or birth trauma or some sort of trauma.
While and that. Yeah, it just adjusts the the the
construction of our brains. Um. Supposedly, a mother's age has
(34:46):
an impact on her kids. That's crazy. Statistically, speaking of
a mother, UM over forty who gives birth is has
a higher likelihood of having a lefty kid, way higher,
like hundred cent or something. Yeah, like that's pretty high.
It's more, I don't even know what that means. Yeah,
(35:06):
and then I guess your hand preference emerges about by
seven months, but then it's like set by age three,
So before seven months, you're just flinging poop with both
hands equally as well. Pretty much. I wrote a story
about a guy who found out as an adult that
his mother had suspected he was left handed when he
was a baby, so she immobilized his left hand so
(35:30):
that he would be forced to learn with his right hand.
He didn't seem to take it like that, but he did.
It came across like he felt like something had been
kind of taken from him. He said. It also explained
a lot that he was like so so with stuff
that involved its right hand seemed to be better with
his left. And um that he looked into it, and
(35:50):
that by doing that, which was very popular like kids
were forced to become right handed through the twentieth century.
Um that you are basically making a a less pronounced
copy of the person. You're taking the original and making
like a slightly dimmer effect simile of it, like forcing
(36:13):
their baying to reorganize like that interesting, whereas they thought
they were trying to give them an advantage, to actually
give them a disadvantage exactly. But I would imagine that
if you did that till say age eighteen, and then
all of a sudden started using your dominant hand that
you were naturally born with. It's all like spin ley
in week right. But then once you once you train
(36:34):
it to to to bulk back up, I would imagine
your brain would would be better off like that and
be fuller. So to continue the abuse right until eighteen
dis continued the abuse and then bam, you got a
super kid on your take your little old man Spinley,
hands and fingers like build them back up? And Mr
Show character remember Titanico and they were crossing the hospital.
(37:01):
You know they're getting back together. Yeah, yeah, that's exciting.
So p FT tweeted something some picture is very excited
the whole gang. If you want to know more about
Paul if Tompkins or Handedness or Mr Show or any
of that jazz, you can type that stuff into the
search bar at how stuff works dot com. Since I
said search, part's time for a listener mail. I'm gonna
(37:25):
call this Christian shout out. Hey, guys started listening to
a few months ago, and I've already listened to about
a hundred and sixty episodes. Um and by the way,
we've mentioned this a lot, but if you're just on iTunes,
say and you think, boy, these guys have got three
hundred episodes three one, Yeah, we've got like how many
now seven change yea seven hundred plus that you can
(37:48):
find on our website. Um. Stuff, you should know dot Com. Yeah,
and as a little pro tip, if you go onto
stuff you should know dot com a k the website
with one of the worst searches in the world. Just
do control F and open up your web browsers search
and then type it in and on our podcast archive page.
If you're looking for something, yes, okay, they'll bring it up.
(38:08):
Don't search for it. Don't bother searching for it using
our search tool. Are we working on that? I hope so,
because this is really bad, like it doesn't bring up
anything really yeah, wow, that's pretty bad. Otherwise it even there,
I don't know. I guess for looks lane. Um. So,
getting back to this, we do have a lot of
(38:29):
podcasts out there, for those of you who don't know,
we have seven hundred plus we're talking about. He's uh,
he listened to a hundred and sixty episodes. His favorite
thing about them is how you don't poop poo anybody's beliefs.
I'm a Christian, So when I was very much so
begrudgingly uh listen to your evolution suite. I was expecting
to be mad, but to my surprise, I heard a
(38:52):
very non bias view of evolution. Um I do believe
in evolution, but it's a long story. By the way,
after many years of hearing creation a slam uh people
talk about evolution is a very pleasant surprise. So I
just want to say thanks for putting your hearts but
not your opinions into that episode. That is from Matt
very sincerely, and uh, we've been taking a task here
and there. We try to do our best, matt um,
(39:14):
to keep things on the level like that, but we
are human and we do uh flounder here and there
with that, but we we try, and we appreciate your
kudos for that. Yeah, thanks man. Yeah, if you want
to give us kudos, we would love to hear about that.
Or if you have any great stories that has to
do with handedness, let us know if you had your
arm tied to your waist till you're eight as a baby. Yeah. Uh.
(39:37):
You can tweet to us at s Y s K podcast.
You can join us on Facebook dot com, slash stuff
you Should Know. You can send us an email to
Stuff Podcast at how Stuff Works dot com and has
always joined us at our home on the web, Stuff
you Should Know dot com for more on this and
(39:57):
thousands of other topics. Does it how stuff works. Dot
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