Happy Left Handers Day

[Cudzoziemiec]

But if people were born 50/50 left and right handed, why would there be a preference in tools etc for one handedness over the other?
...
and Helly observes handedness in very smalls. It seems more likely that we're just born primarily right-handed. Perhaps there is some evolutionary advantage on a population level to having most of the species handed in the same way?

It's an interesting question, but I think once there's a small benefit to going one way or the other, it gets amplified by design and environmental choices (the same happens in evolution, but I think can applied to non-heritable phenotypes). There must be an overall selective benefit in handedness itself, otherwise you wouldn't see it in other primates, but not in which hand is dominant. I'd speculate the benefit on handedness in tasks is the focus – both on building the neural structures for fine control (on either side of the brain) and the basic stamina and strength to perform that task.

Yes, I'd speculate on the same lines. But doesn't that suggest that most individuals of a largely z-handed species will be born z-handed? There might be some y-handers who get "converted" by use of tools etc but surely most are going to be born in line with the majority of the species?

There might also be an advantage to maintaining a small pool of y-handers for those tricky situations when z-handedness is awkward due to limited space etc. (The classic example would be those spiral staircases in medieval castles, when you'd send the lefties up first so they can swing their swords better; though I expect that's more of a later rationalisation of something that just was.)

[drossall]

Is it unusual? Surely this sort of thing is defined by how easy it is to access a space to get a tool in? Screwdrivers, spanners, hammers, all tools really - everyone must surely use those with either hand depending on where the space is, no?

When there's limited space, yes, but in most instances there isn't, so I'll use my preferred (left) hand. And, where for example a screw is difficult to drive in, there's no doubt that my left hand is better at putting load on (to stop the driver from slipping out of the slot).

[Efrogwr]

I read somwhere that Korean shipyards employ left handed welders and painters so that important parts os structures that right handers can't reach easily are done correctly.

[ian]

...
Yes, I'd speculate on the same lines. But doesn't that suggest that most individuals of a largely z-handed species will be born z-handed? There might be some y-handers who get "converted" by use of tools etc but surely most are going to be born in line with the majority of the species?

There might also be an advantage to maintaining a small pool of y-handers for those tricky situations when z-handedness is awkward due to limited space etc. (The classic example would be those spiral staircases in medieval castles, when you'd send the lefties up first so they can swing their swords better; though I expect that's more of a later rationalisation of something that just was.)

I think the evidence, as far as I've read, is that we're not born with any innate handedness, it's purely environmental (perhaps left-handed people are simply those who did their first scribbles with that hand and stuck with it). Things could, quite reasonably, be the other way around with laevos ruling the roost. As it stands the world is a bit easier for right-handers, so there's more.

[Phil W]

But if people were born 50/50 left and right handed, why would there be a preference in tools etc for one handedness over the other?
and Helly observes handedness in very smalls. It seems more likely that we're just born primarily right-handed. Perhaps there is some evolutionary advantage on a population level to having most of the species handed in the same way?

As pointed out above left handedness was considered sinister, as in cack handed, as in the devils hand.  Until relatively recent times using primarily your left hand was strongly discouraged, certainly in this country (and a few other I can think of).  My uncle was forced to use his right hand throughout school days and at home and elsewhere during his youth.  We are talking about the 1950 / 60's so not a huge time ago.

At school they tried to force me to primarily use my right hand, but left handedness won out.  I had to get left hand nibs for my ink pens. Many of the first things kids come across in school are predominately designed for using with the right hand. So some may just decide to overcome their preference and use their right hands, because it is easier with such tools.

Who knows whether tools would be handed at all, if left handedness had not been associated with the devil?  We also cannot be certain of what percentage are left handed. It's not as if it is recorded in any medical records anywhere.  The number of left handers is anecdotal bit like estimated sexual orientation percentages are far from exact.

[chrisbainbridge]

Left handedness remains a complex subject with a vast number of factors all having a small independent effect. This study is a useful summary https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6345846/

[Kim]

Who knows whether tools would be handed at all, if left handedness had not been associated with the devil?

Because some tools are inherently chiral?  Scissors, for example, can be made one of two ways round.  Same goes for anything involving a screw thread.  And eventually the other kind turns out to be useful - eg. to stop things unscrewing in operation, or to frustrate people trying to obtain the right type of RF connector.

Standardisation is useful, if only to know which direction to apply ham-fisted monkey force to undo that fastener, so it stands to reason that one type would proliferate, even if there weren't any value judgements applied.

When the devil eventually gets invented, it's presumably into a world where one handedness (of both stuff and people, if only through learned techniques) is more common and considered normal, so naturally he's going to get associated with the other.  First rule of persecuting out-groups for political gain is to make sure your chosen out-group are in a weaker position, if only by force of numbers.

I'm sure the Raman devil was associated with right-tentacledness.  Or something.

[ian]

If it's any consolation, movies always get DNA the wrong bloody way around. It twists to the right.

(There's no known reason why it can't be left-turn, the same for amino acids which, for life on Earth, are all L-)

[caerau]

There's plenty of experimental evidence for symmetry breaking events in molecular populations leading to a rapid self-selection of the predominant isomer once it becomes the slight majority.
(in designed, self replicating systems... it's a fascinating subject actually 


Symmetry breaking even goes as far back as the Big Bang if you *really* want to get into it - why is the universe made from matter particles and not, what we call, anti-matter?  A symmetry breaking event right at the outset must have started that one...


(aslo, pedantry-wise... D-amino acids do actually exist in nature, quite a lot - presumably you meant DNA-encoded proteinogenic amino acids are all L- )

[Jasmine]

Is it unusual? Surely this sort of thing is defined by how easy it is to access a space to get a tool in? Screwdrivers, spanners, hammers, all tools really - everyone must surely use those with either hand depending on where the space is, no?

When there's limited space, yes, but in most instances there isn't, so I'll use my preferred (left) hand. And, where for example a screw is difficult to drive in, there's no doubt that my left hand is better at putting load on (to stop the driver from slipping out of the slot).

 
Ok, so how about cooking? Say you have 4 pans on the hob. To avoid overlapping handles, the 2 pans on the right side have handles sticking off the the right. The 2 on the left have handles sticking out to the left. You want to stir the contents of the pans. Surely for the 2 pans on the right side, you hold the pans with your right hand, and stir with the left; but for the pans on the left side, you hold the handle with the left hand, swap the spoon over and stir with the right hand?

[Phil W]

If it's any consolation, movies always get DNA the wrong bloody way around. It twists to the right.

(There's no known reason why it can't be left-turn, the same for amino acids which, for life on Earth, are all L-)

Brilliant, all life on Earth is made from left handed molecules. Everybody on Earth is left handed.

[ian]

If it's any consolation, movies always get DNA the wrong bloody way around. It twists to the right.

(There's no known reason why it can't be left-turn, the same for amino acids which, for life on Earth, are all L-)

Brilliant, all life on Earth is made from left handed molecules. Everybody on Earth is left handed.

Apart from DNA, of course. That's D-.

(aslo, pedantry-wise... D-amino acids do actually exist in nature, quite a lot - presumably you meant DNA-encoded proteinogenic amino acids are all L- )

Yes, proteins, you pedantic monkey. If I recall, bacteria use D-amino acids in their cell walls (and glycine is its own enantiomer, so doesn't have D- or L- forms). Excitingly my final foray in the heady heights of academia was nucleic acid-sugar epimerisation.

It's important stuff, the problems with thalidomide, for instance, were down to stereochemistry.

[Cudzoziemiec]

Surely the lefty-devil association is pretty strong evidence of left handers being a minority. Or could it be that the 50% of the population that's right handed got a random advantage over the others at some point – presumably about the time we started using tools – and for some reason began persecuting half the human beings on earth?

I wonder how far back that association goes though. 2,000 years certainly, probably 4,000. Come to that, do we have any evidence of handedness in archaeological remains? Maybe cave art would give clues?

[Mrs Pingu]

Is it unusual? Surely this sort of thing is defined by how easy it is to access a space to get a tool in? Screwdrivers, spanners, hammers, all tools really - everyone must surely use those with either hand depending on where the space is, no?

When there's limited space, yes, but in most instances there isn't, so I'll use my preferred (left) hand. And, where for example a screw is difficult to drive in, there's no doubt that my left hand is better at putting load on (to stop the driver from slipping out of the slot).

 
Ok, so how about cooking? Say you have 4 pans on the hob. To avoid overlapping handles, the 2 pans on the right side have handles sticking off the the right. The 2 on the left have handles sticking out to the left. You want to stir the contents of the pans. Surely for the 2 pans on the right side, you hold the pans with your right hand, and stir with the left; but for the pans on the left side, you hold the handle with the left hand, swap the spoon over and stir with the right hand?

Weirdly, given my screwdriving ambiguity, no.

[Efrogwr]

Is it unusual? Surely this sort of thing is defined by how easy it is to access a space to get a tool in? Screwdrivers, spanners, hammers, all tools really - everyone must surely use those with either hand depending on where the space is, no?

When there's limited space, yes, but in most instances there isn't, so I'll use my preferred (left) hand. And, where for example a screw is difficult to drive in, there's no doubt that my left hand is better at putting load on (to stop the driver from slipping out of the slot).

 
Ok, so how about cooking? Say you have 4 pans on the hob. To avoid overlapping handles, the 2 pans on the right side have handles sticking off the the right. The 2 on the left have handles sticking out to the left. You want to stir the contents of the pans. Surely for the 2 pans on the right side, you hold the pans with your right hand, and stir with the left; but for the pans on the left side, you hold the handle with the left hand, swap the spoon over and stir with the right hand?

I move all the pans around so that I can hold the handle with my right hand and stir with my left.

[Kim]

I'd probably stir the front right pan right-handed (handle sticking out to the front, at least temporarily during stirring).  I'd swap hands for the one at the back.

[Adam]

I'm originally left handed, although I'm another one where at school they tried to make me use my right hand.  So I can write with both hands, at the same time if pushed (which really freaks out some people), although I'm much slower with the right.  Although it's much neater.........…

Having said that, over the years, I've ended up ensuring I can use either hand for just about anything, as it's just easier that way.

[ian]

I was never made to write with either hand but then I suspect my teacher gave up after her failed attempts to make me join up my letters. This boy won't do the Devil's Cursive.

[hellymedic]

I was never made to write with either hand but then I suspect my teacher gave up after her failed attempts to make me join up my letters. This boy won't do the Devil's Cursive.

I am convinced joining up letters just Does Not Work for some people, of whom I am one.

My joined up writing was never fluid and quick, and joining up just made it scrawly. Unjoined, it was crisp and clear.

[Jaded]

The more important question with the cooker and pans is stirring clockwise or counterclockwise with each hand?

If I try to unlock a door with the wrong hand I fail as I am trying to lock it more.

Regarding hammers and screwdrivers, a surprising number of the occasions when you need these are in corners. It is in corners that ambidextrousness is exceptionally useful.

I know I've posted this before, but a long time ago, in a former century, I had a job packing diesel engines. The engines arrived, were lined up by a forklift on pallets, and we built a crate around them, out of wood and nails. I joined the team along with another newbie, time served in one of The Forces. The regular staff aligned themselves to the latter, and I was out on a limb. Until the next day when I turned up for work and he didn't. Apparently he couldn't get out of bed because his arm hurt so much. He'd only used one arm to hammer in nails, poor soul 

Later on that week I worked out how many nails we each hit in a day. I seem to remember it was in the order of 1/3rd of a mile of nails a day.

They wouldn't do that nowadays, they'd do it in metres.

[Kim]

The more important question with the cooker and pans is stirring clockwise or counterclockwise with each hand?

Both, for better mixing...

[Cudzoziemiec]

And related, what about writing an 8 or O? I feel sure there's a "correct" direction for these, that you're taught at primary school, but I've no idea which direction it is. I sometimes do them one way, sometimes the other, but I always start at the top. That's about as ambidextrous as I get though.

[Kim]

'8' and 'O' I start at the top heading clockwise.  '0' I start at about 2 o'clock and go clockwise, before adding a stroke downwards and to the left.  (I cross my 7s too, but this doesn't solve the problem of Other People sometimes doing '4's that look like my '9's (my '4's look like '4's, so are completely unambiguous - I used to provide a sample in the margin of exam papers).)

If I were to slow down and bit-bash the primary-school joined up writing I haven't used since about 1995, I'd do 'o' the anticlockwise from the top.

It seems that a surprising amount of the handwriting I actually do these days is numbers:  Noting down measurements, network addresses, writing dates on things, occasional scribbles of algebra.  The occasional post-it note gets block capitals.  I tend to use a computer of some sort for everything else, which is to the general benefit of humanity.

[Cudzoziemiec]

So your 4s don't look like Ss? I once had a taxi ride in Poland during which the driver expounded to me his cranky theories of numerology and the significance of letters. The only bit I remember is that 4 is the number of power, lightning and violence. As he pointed out, the Nazis knew this; think of the SS.

(Q I definitely start at the top and go anticlockwise. The others I start at the top and go either clockwise or anti. And I cross my 7s too. I can't remember if that signifies anything... )

[JennyB]

Presumably there's a benefit to consistent handedness once working in groups with tools becomes a thing.  I'm thinking clobbering animals to DETH with sticks without hitting your friends, rather than the practicalities of sharing scissors.

When I took up archery they always made me stand on the right end of the line.