h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I've got a weird set of handednesses... (and that's a weird word...)

I write with my left hand. I play tennis, squash and badminton with my left hand... although I'm probably 80% as good with my right. I play golf, softball and cricket (incredibly badly) right handed, and can't even *begin* to play them left-handed. I surf and snowboard goofy, but so did HB and she was righthanded, and when my fencing instructor tested me to see which eye was dominant he pronounced that I didn't have a dominant eye but was perfectly laterally balanced. Which was nice.

The main disadvantage I've found being left handed has been in the 70s when I was learning to write I had a crappy biro that leaked a bit, and being left handed meant I smeared the ink as I went. Right handed people didn't do that. I also, until the age of about seven, had that "wrapping the hand over the pen" thing going on that a lot of left handers seem to have, until a teacher cured it by the simple expedient of telling me not to do it, then hitting me hard on the head with the edge of a ruler if she ever saw me doing it.

I've noticed that a disproportionate number of my colleagues in the engineering profession are left handed.

SoRB

From what I've read, whether you're left or right handed depends on this: (hopefully I can get this into clear English ... it's late & I should be deeply slumbering ... here goes):

There are far more twins conceived than are born, due to a number of factors such as the mother's ability to carry two foetuses (nutrition, general health etc.). The unviable embryo is either reabsorbed or ejected. The estimated number of us who began our 'life' as twins is 1 in 12.

There are 3 types of twins, but we are interested in identical twins here. There are two different types of identical twins, those who are exactly identical and those who are 'mirror' twins i.e. if one has a left-curling cowlick, the other will have a right-curling cowlick in exactly the same position ... are you still with me??? Do you see where this is going??

One of these mirror twins will be right handed, the other left handed. That, I have read in books on paediatrics, is why there are far more right handed people than left handed. Left handed people began their life in the womb as the mirror twin of an unviable 'other'.

Twins run in families: I was one of two, but my sibling miscarried at 5 months. My father was left handed, and I can only conclude from this information that he was originally one of two as well.

Well that's my worth ... for what it's worth.

Hmm, sorry but I don't buy that.

Are identical twins always such that one is right-handed and one is left handed? Please correct me if I'm wrong but I don't think so,

In addition if only 1 in 12 of us is a surviving twin in your scenario, then this only explains 1 in 12 cases. With 95% of the population (or whatever it is) being right handed then this theory cannot explain the majority of cases.
Ie. 11 out of 12 right or left handed people are not covered by this theory.

I think I'm with Orcus, although the left-handedness rate is normally put around 10% for the population, with men twice as likely as women.

There are people who are left-handed because they are mirrored compared to the norm - either in the whole body or in brain-hemisphere use, but they only make up a relatively small chunk, and there are right-handers who are mirrored as well.

oh come on.

Everyone knows lefties are all aliens.

Same as red haired people. (presumably red haired lefties are the result of interbreeding between the two alien species.)

Oy!

Well, superior aliens. Kneel, Earthling.

I'm a lefty and am not surprised they used to persecute us weirdos centuries ago.

The thing I find oddest is using a mobile phone. If I'm walking down the street, I'll answer with my left hand (fairly obviously). But if the conversation goes on a bit and I swap to the right hand, I find I can't walk anymore. I realise that I've stopped and held onto something like a lamppost.

Maybe I should've been drowned at birth?

There's this on the subject of lefties and phones: A4888399

Paff

Hmm. I'm a right handed female who uses the left ear for phones, throughout even a long conversation. I'll swop hand but not ears.......

So I'm a good listener?

It intrigues me when I see people pick up a phone with one hand, then swap to the other side in order to free their writing hand.

I wonder why we have this handedness thing. Or eyed or toed or legged or whatever. This asymetry in the control of our bodies.
Clearly, since some people are ambidextrous, or ambiocular(?) like SoRB, it is perfectly biologically possible to not be biased one way or t'other. The question is, I suppose, whether handedness (which I use as a loose term for all such bias in control) is an adaption to fit a particular environmental pressure, or a side effect of something else that has yet to prove disastrously unbeneficial and thus be bred out. But it is weird that right handedness is o prevalent, and also that other apes who have developed tool use show handedness.
I also wonder if ambidextrousness is a special case of handedness (I.e. that person has both left handedness and right handedness at the same time) or if it is some sort of base from which the rest of us differ by defect. I.e. there is some common defect which causes us right handers to lose the fine control of our left hand, and a similar but less common one for left handers. Is ambidextrousness the default perfect control state for humans? Or a strange abnormality?

Some of the things, scattered around the internet, that I've read on this were skeptical that anyone was truly ambidextrous. They argue its likely a case of mixed dominance - i.e. ambidextrous people will usually be better with the left hand for some tasks and the right for others.

I think it is worth bearing in mind just how easy symmetry breaking is to achieve and just how much effort it is required to be perfectly symmetrical.

It would really be very difficult and take a conscious effort to use one hand EXACTLY fifty percent of the time and the other for the other 50%. Once you forget the assymmetry is very likely to be self reinforcing as you will quickly get better practice at doing something with the hand that even unconsciously gets biased. Once that better practice is there it will obviously be more comfortable to use that hand for this purpose...even better practice...etc. etc.

Ictoan, I've heard that all red-haired people are descended from Neanderthals and that 10% of Scots have red hair.

I think current thinking tends to shy away from neanderthal/cro magnon interbreeding. Leastways thats what I've been told a few times I have mentioned it.

Saw this on the BBC site, interesting consequences of left/right-ness

http://news.bbc.co.uk/1/hi/sci/tech/4831218.stm

"Snails with left-handed shells can have a big advantage in life - predators may find it impossible to eat them. They found the crab is unable to open left-handed shells because it only has a tool for peeling them on its right claw; so it discards them. "

Yesterday we were looking at an antique model of a solar system and the owner told my girlfriend to wind it up. Being left-handed she turned the handle the wrong way - oops - nothing happened - lucky she didn't break it.
Fortunately the owner managed to get it going - using his right hand.
Could have been worse - could have been God messing with the real thing!!!!!
Aaaaarg.....

ps - that's an 'orrible lookin' crab you've found there no wonder he can't find a girlfriend --- or is that the snails --- I'm totally confused no w ....

I write with my left hand, and I throw things with my left hand, but thats about it, I use scissors with my right hand, I'm right foted, I aim a snooker cue with my right hand, I even have better eyesight in my right eye!

So does this mean i'm ambidexterous? Or is that just appliciable to people who right with both hands? So this 25% stuff, and the whole genetics theory about only one in four people are left handed... does that apply to using their left side for everything? I know that one side is supposed to have dominance over the other, but I have many friends that are left handed, and all of them are pretty much the same as me in that they write with their left hand, but do virtually nothing else with it.

Hm. Next time I see P. (Deaf friend of mine) I must ask him why he signs with his left hand dominant though I've been told he's actually right-handed generally.

TRiG.