Why Are People Left- (or Right-) Handed?

Live Science ^ | November 10, 2019 | Megan Gannon

[SunkenCiv]

While there's no righty or lefty gene, DNA does seem to play a role in handedness. In a recent study published in Brain: A Journal of Neurology, researchers at the University of Oxford looked at the DNA of about 400,000 people in the U.K. and found that four regions of the genome are generally associated with left-handedness. Three out of these four regions were involved in brain development and structure. Some researchers hope that studying the biological differences between lefties and righties could shed light on how the brain develops specializations in its right and left hemispheres...

Righties have dominated for as far back in the archaeological record as researchers can see, about 500,000 years, Uomini said. Neanderthals, our now-extinct human cousins, were also strongly right-handed.

That makes humans pretty strange among animals. Several nonhuman species, such as the other great apes, are individually handed, but the split between righties and lefties is typically closer to 50-50.

What caused our extreme bias toward right-handedness to evolve and persist? From an evolutionary perspective, if right-handedness evolved because it had some kind of advantage, then you might expect left-handers to disappear completely, Uomini told Live Science. She added that there are some disadvantages to being left-handed, such as higher frequencies of work accidents. Researchers also linked left-handedness to learning disabilities, in a study published in 2013 in Brain: A Journal of Neurology.

But there's a leading theory to explain why left-handers have maintained a constant minority: the fighting hypothesis.

"The idea is that in hand-to-hand combat, or in combat with weapons, there is an evolutionary advantage to being a minority left-hander," Uomini said. "If you're left-handed, you have a surprise advantage because most people are used to fighting against right-handers."

[SunkenCiv]

This sounds like a crock to me -- obviously the same disadvantage a righty might experience confronted by a lefty applies reflexively, a lefty would have the analogous disadvantage confronted by a righty. This is an example of straw-grasping, and the idea is foolish. The fact that left-handedness persists shows that there is no natural selection, that genomic survival, which is a matter of chance, is the only thing going on.

Hat tip to Lew Later:

Why Are People Left Handed? | LaterClips | November 20, 2019

[piasa]

Left handers are pretty good at confounding righties in baseball.

[SunkenCiv]

https://www.sciencedaily.com/terms/left-handed.htm

The Association between Handedness, Brain Asymmetries, and Corpus Callosum Size in Chimpanzees (Pan troglodytes)
William D. Hopkins,corresponding author Leslie Dunham, Claudio Cantalupo, and Jared Taglialatela
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2018751/

Most Neanderthals were right-handed like us, researchers find
By Megan Gannon
News editor
updated 8/24/2012 2:01:05 PM ET
http://www.nbcnews.com/id/48781052/ns/technology_and_science-science/t/most-neanderthals-were-right-handed-us-researchers-find/

[SunkenCiv]

Oklahoma Pre-K teacher allegedly calls being left-handed ‘evil’ and ‘sinister’
kfor | September 21, 2015 | Abby Broyles,
Posted on 9/22/2015, 1:46:31 PM by JoeProBono
http://www.freerepublic.com/focus/chat/3339926/posts

[Bitman]

a lefty would have the analogous disadvantage confronted by a righty

I disagree. For the lefty,being confronted by a rightly would be normal. The lefty would also have a disadvantage when confronting a lefty.

[RandallFlagg]

The video surveillance of the attempted robbery at that phone shop (I don’t remember where, but it was this year) showed the armed defender shooting the perp left handed.
Dude was QUICK!
Moved to his left, drew from his left, dropped the punk and ran out to call police.

[AndyJackson]

Not a crock. A leftie gets to practice against right handlers all the time. The other way not so much.

[abclily]

Left handers are usually artistic.

[Yo-Yo]

Two thoughts, and I am too lazy to do a Google search:

1) I thought in the animal kingdom that "handedness" was roughly 50-50, so it was culture that made humans right hand dominant.

2) I thought I have also heard that left handed people also have their brain functions mirrored, analytical and creative sides are flipped from right handed people.

What does this study say about ambidextrous people?

[ComputerGuy]

Based on my experience, it seems that lefties like me are overly-represented in software development. LH women even more so.

[OttawaFreeper]

Left handed, but not left leaning.

[Tennessee Conservative]

So what causes a person to be both? I don’t know if I qualify as ambidextrous since I can only do certain things with a certain hand. I’m typically a lefty since I write and eat with my left hand. I do everything else with my right hand. I shoot, throw a ball, use tools, and everything else right-handed. I have a lot of confusion when somebody says turn left or turn right. I have to stop and think about something that comes natural to most people.

[Jim Noble]

Once when I was a manager of a Little League team, I happened to draft an 11-year old lefty who wanted to pitch.

Now, this kid turned into an Olympic athlete later on, so I’m not claiming his innate ability had anything to do with me.

But the first time an 11 or 12 year old who has already learned to hit a baseball facing right handed pitchers has to face a fireballing left hander is a riot to watch.

[Blueflag]

Bad logic in the title, in that its presented as a OR.

I am profoundly ambidextrous, meaning I show no definite tendency either way. Does not mean equal left and right.

I write left handed on paper but right handed on a whiteboard, yet can write left handed on a whiteboard as well.

I putt left handed but the rest of my game is right handed. I can play tennis with either hand, but serve right handed.

Most importantly I can wipe my butt with either hand, important if one hand is injured.

;-)

YOu should get the idea.

Handedness is not always an OR.

[OrangeHoof]

Back in the early 1980s, pitcher Bill Lee, a noted oddball, was interviewed about being lefthanded. He replied:

“Science tells us that righthanders are dominated by the left half of their brains and lefthanded people are dominated by the right half. So there’s proof right there that lefthanders are the only people in their right minds.”

My grandmother was born in 1900 and grew up lefthanded. Later, it was discovered that she had been born with a broken right collarbone explaining why it hurt to do things with her right arm so she naturally learned to write, throw, etc. with her left arm because it didn’t hurt.

I have seen people born with no arms learn to do incredible things with their bare feet so our limbs can adapt to make up for the lack of other functions.

[I want the USA back]

“then you might expect left-handers to disappear completely”
Dumb assumption. The human body is not completely symmetrical. Heart, liver, stomach, appendix, intestines, lungs and brain. Explain the lack of symmetry before getting into handedness.

[newfreep]

As a kid, I threw right, batted left & right but always had more power batting left.

As a teen, I took up golf as a lefty and tennis as a righty.

At 12, the City of Dayton,OH honored me as one of the best LL players in the city....so I guess I was doing something right. I had dreams of being a ML player...until this petite blue-eye blonde moved next door and my interests changed.

I always wondered what could have been. In LL, I had a .800 batting average and the kid who was our catcher batted .200...and later became the starting catcher for the LA Dodgers (Steve Yeager). Even in LL, he had one hellava arm!

[Bitman]

I am very similar. Learned things such as writing and holding a fork for eating are left handed. Natural things such as throwing a rock are right handed. I can do most things with either hand, but it does not feel comfortable,
nor is the result as accurate and smooth as with the preferred hand.
Just for kicks, I used to practice writing with both hands, simultaneously. It was the same sentence i would write with both hands as I am not THAT weird.

[csvset]

I eat left handed as well. I was able to write or bat either hand , just fell out of practice .

[piasa]

Left handers are also less confused when facing right handers because there being more righties, everything is made for righties and everything is done from the perspective of righties. So from birth on the lefty is faced with a righty world and learns to deal with it, making most lefties become ambidextrous either in part or in everything when they must. That may change since left handed products are now easily available.

I think the researchers are thinking too much in an eithor/or way and haven’t really thought about the lefty’s forced ambidextrousness [or the righty’s dependence on their right hand from a life of ease in never being required to learn to use the left hand] being the real advantage against right handers in baseball, etc.

My parents and grandparents had a lot of kids and about half were left handed when writing or dining out of habit but could use the right hand albeit more clumsily for these tasks. Of those, all could easily use their right or left hands for shooting, fly fishing, driving nails or using tools, playing baseball, etc. with no clumsiness, while the same could not be said for the right handed kids. Right handed siblings were strictly right handed, no ambidextrousness at all.