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

Why isn't there a 50/50 division of left-handed and right-handed people? Is it something to do with the heart being on the left side of the body?

Could it be that because they are clumsier than us right handers they remove themselves from the gene pool more readily?



*Waits* 10....9....8....

Handedness is complicated, and involves other factors too, but is broadly rooted in genetics. The right-handed gene (call it 'R') is dominant and the left-handed one (call it 'r' - geneticists always use the same letter) recessive. That means a person with one gene of each (Rr) will still display right-handed traits.

You get one gene from each parent, so there are four potential combinations: RR, Rr, Rr, rr. Only one of these four will be left-handed.

This is the simple genetic model which Mendel and his pea plants came up with. In actuality there are many other environmental and genetic influences on handedness, so it's not quite as simple as that. But the clear fact remains that right-handers should comfortably outnumber left-handers.

B

That lefthandedness is at about 10% (not 25%) of the population points to the trait not being a simple Mendelian one (not 1:2:1 or 9:3:3:1), but a complex, polygenic trait. I don't think much of the developmental genetics of handedness is known - we don't know much about development at all right now.

I'll have a look at the quantitative genetics of handedness, see what I can find.

Ste

I've noticed that you can tell if a person is right or left handed by the way they clap. The dominant hand is the striking hand. Have got the impression that the number of lefthanders are more than 10% when I've watched people applauding at certain classical concerts and the theatre ... artistic types you might say.
I wonder if anybody has surveyed groups such as classical pianists, composers, famous actors etc. for handedness? Is it the same as in the general population I wonder?

I've heard that mathematicians are more likely than average to be lefthanded, but I don't know about the others.

Change of handedness is often associated with "hemispherical dominance" (lefthanded people tend to be good at patterns, poor at language), but in a small numer of people it seems that the organisation of the brain is a mirror image of the normal (language centre in the right hemisphere).

Noggin

Further to the previous posting I wondered if people could activate parts of the brain currently lying more or less dormant by transfering simple tasks to their weaker hand (in my case to my left hand) e.g. combing my hair, brushing my teeth, picking up the coffee cup and so on,
and thereby stimulate the building of new brain connections.
Would it be useful for the elderly to try this to prevent the onset of senility?

Left-handed people do tend to be more arty.

I think its because the right side of the brain is the more creative side of the brain.

http://www.angelfire.com/wi/2brains/


Hmmm, I *should* be ambidextrous then!!

a friend of mine from school is left-handed. she was extremely bad in math. she could somehow get along with algebra. but geometry was the absolute disaster for her . she is a dentist now
so i guess left handness (curious word. i doubt that it exists at all ) and math doesn't always go togehther.

by the way, i always thought that there is something special about left-handed people. don't know why. they seem weird to me in a very sympathetic way

It is amazing how many actors, artists and art critics have said they wasted their time doing Maths at school as they were completely useless at it. Presumably, their English was good. I always had the feeling that they *should* be bothered *and* embarrassed about not being able to do Maths but if it is because they a right-brain dominant then that is a good reason. But as they probably do not actually realise WHY they are bad it still looks bad on them. It would be great if an artiste! actually said 'Well, of course my maths is awful, I'm right-hemisphere dominant!'.

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The correlations are only statistical, and relative to the population as a whole. As has already been said there isn't only *one* reason for being lefthanded.

Noggin

Don't start on stats Noggin, those Right-brained people won't know what you are on about.

And <<...not being able to do Maths but if it is because they a right-brain dominant then that is a good reason.>>

That mathematicians are statistically more likely to be lefthanded than average (as opposed to being more likely to be lefthanded) means that they are *more* likely to be right hemisphere dominant (the right hand is controlled by the left hemisphere, and vice versa)

Noggin

Alfster,
there's a more scientific test at www.sseah.se
but your looks more fun to do at parties.

Im left handed but my right hand is stronger than my left, So I dont understand how thats supposed to work

www.sseah.se gave a rather pleasant result for me it coincide with my idea of me

Wow, that was scarily accurate in how I am. I am ony very slightly right hand biased.

It does capture my slightly weird way of thinking which is in a way good as I know there is a reason for it!!!

A darn shame you can only print the analysis but doing a 'print screen' and paste into a word document also works.

Thanks.

yep, looks accurate to me as well. i'm wondering what would be the result if i make it again?

I've got to look at the test. But although mathematically you'd expect 25% left handed people, not 10%, would the fact that for hundreds of years lefties were considered evil, and often killed/executed, affect the proportions?

Originally cack-handed had the same meaning as left-handed, whereas now it's more likely to mean clumsy.

Or have I just made all that up?

You would not expect 25%.