Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: thedoc on 13/07/2015 13:50:01
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E HISCOX asked the Naked Scientists:
I would like to know the answer to the following questions if possible....
Why are more people right handed than left handed?
Do you still broadcast on Radio Cambridgeshire at 6pm?
I used to listen when you were on 3 counties radio a while ago.
CATHERINE
What do you think?
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Handedness is a peculiar phenomenon. Most distributions in nature are either fairly even (male/female ratio in mammals) or very rare (reverse heart anatomy) but lefthandedness seems to occur somewhere in the 10 - 25% range.
My hypothesis is that about half of the human population is genetically incapable of being lefthanded, due to the brain having to learn all sorts of difficult things like standing on two feet, and talking. Quadrupeds and animals with a smaller vocabulary don't seem to be particularly handed in comparison. So in about half the population all the complex motor skills are, say, lodged in the left half of the brain whereas the other half of the population they are distributed more evenly.
Now society requires us to abide by certain hand conventions, and half of us can't use lefthanded tools, so the general convention is to use the right hand for fine motor control. This gives 50% of the population a choice to go with the flow or be different, and by Bayesian statistics about half of the "born ambis" choose to live as dextrals, possibly enjoying some advantage in twohanded skills like music and sport, whilst the remainder (which may include a very few "genetic sinistrals") use the left hand.
This may explain a few observed phenomena: a signficant number of lefthanded "creatives" including many composers (though few instrumentalists), mathematicians, and high-flying executives (lefthanded CEOs apparently earn 10% more than righthanders in FTSE companies) and politicians.
There was a reported association of lefthandedness with speech and hearing defects but AFAIK this phenomenon is statistically weak. I think there may indeed have been a case some years ago when schools insisited on righthanded writing, that the few who simply couldn't do it were "genetic sinistrals" and may indeed have had genetic problems of coordination, but with a more tolerant education system they have been diluted by the "lefties of choice".
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I think there may indeed have been a case some years ago when schools insisited on righthanded writing, that the few who simply couldn't do it were "genetic sinistrals"
Quite a few in my class at school were forced to write RH and described as cackhanded. LHness used to be associated with the dark side as in your eg of sinister, see also difference between adroit and gauche from right left.
Not many people realise that most of us are right-eyed. Check it out, keeping both eyes open, point your finger at a distant object as if pinting a pistol. then close the left eye. For most people the finger and object are still aligned. Now close right eye, for most people the object will appear to be to the left of the finger. Or is it the finger is to the right of the object?
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If it were down to a right hand gene allele vs. a left hand allele then why don't you see it follow Mendellian paterns of inheritance? Why can't you breed a race of southpaws?
An alternate explanation is that the left hemisphere of the brain controls the right hand also. So it is easier to have the speech side working the dominant hand.
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I think there may indeed have been a case some years ago when schools insisited on righthanded writing, that the few who simply couldn't do it were "genetic sinistrals"
Quite a few in my class at school were forced to write RH and described as cackhanded. LHness used to be associated with the dark side as in your eg of sinister, see also difference between adroit and gauche from right left.
Not many people realise that most of us are right-eyed. Check it out, keeping both eyes open, point your finger at a distant object as if pinting a pistol. then close the left eye. For most people the finger and object are still aligned. Now close right eye, for most people the object will appear to be to the left of the finger. Or is it the finger is to the right of the object?
I closed my left eyes and everything went blurry. No, seriously. When my eyes are normal closing one different eye gave different perception of position, whether I closed my left or right eye.