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

This is something that has always puzzled me. Why are some people left handed?

Why is it that a minority of people are left handed, why isn't it 50:50?

The same is true with the right and left hemispheres of the brain. In most people, the left does the logical bit and the right side does the talking bit (broadly speaking). In some people this is reversed, and most, but not all, of these people are left handed. Likewise, some people with their brain the right way around are left handed.

What's going on?

D.

Hmm, I think you got the part about the brains wrong.

Funny that; I've just written something about the two halves of the brain (it's currently going through PR... at the mo... but it's not a plug...)

Two Halves: One Brain

http://www.bbc.co.uk/h2g2/guide/A655337

Not everything you need to know, as we haven't found everything yet...

Stay ,
WD

My mum is left handed. She always says that left handed people are the only ones in their right minds!

I found something interesting somewhere. I don't know wether it is true or not. It was that every year there are 2500 left handed people in the world, that die from incidents with things made for right-handed people.

Don't know, but I think there's a difference in avrage lifespan against LH people.


Dancer

I heard somewhere that being left-handed is the result of a very slight bit of mental retardation in the brain, or something to that effect. I'd assume that's a very common condition, since one of 9 people are left-handed. I myself am LH, and I have two cousins (they're brothers) and an uncle (their father) who are LH, so I speculate that it might be hereditary.

i suspect the opposite there is no one else in my family whose left handed that i know of.

Retardation is probably the wrong word. It seems to be that people usually use the left half of the brain most. While a few use the right half most. And those are left handed. Right half controls left hand and vice versa. But 1 in 9, that is a big number.

It's the wiring. Very little of the brain is actually hard-wired...basically the hind brain that deals with the breathing and basic's. And to be honest with you on the hereditary thing, it could very well be, as with anything else, as bit of both....Hereditary in some families and sporadic in others.
Not that we'll ever really know what causes it...just like it is unlikely that we will find all the factors that decide height, hair colour, eye colour and such stuff. At least not in my lietime...or that os my sisters kidies..

I believe it's determined genetically by a number of genes, at least some of the alleles that cause left-handedness for it being recessive, hence it being less common than right-handedness, and definitely not a 50:50 split as might be expected from codominance.

For some reason, right-handedness is dominant. I don't know why, I don't think anyone knows why - it's like blue eyes. They're caused by recessive alleles - but why? Why should blue be recessive and brown dominant? It doesn't seem to make any sense, but that's just how it is.

More of the random chance coming into evolution there I think.