[mike2niner4 (OP)]

Hey,

I've wondered why some people are right and some people are left handed? Is it just a random thing that occurs in nature, is it a mutation like blue and brown eyes?

Thanks, Mike

[lucyejo]

sure everyone is born ambidextrous if that's how you spell it, ad its a matter of which is used more in early days, becomes habbit and obv the strengthening of muscles etc. always what I've thought anyway.

[JnA]

New mothers are often advised to hand their children things through the centre line.. that is not selecting a hand to pass them something.
Peads check newborns for differences in sides.. they want the baby to be equally strong on both sides.. this is normal in newborns. Mothers often notice that one hand is clenched more or one arm is waved more. Studies of these show that the 'preferred' hand is equivalent to the ratio of left and right handedness in humans.

Children will use both hands but often show a preference early. This becomes more obvious as they develop greater muscle control.. but you will still find toddlers using pencils with their 'non preferred hand'. Hand choice isn't usually reliable until about four.

The percentage of left-handed people is pretty constant around the world, with *some* regional variations.. No culture is known in which there are equal numbers of left- and right-handed people, a strong argument that the cause of handedness is biological, not cultural.

I used baby signing with my children and noticed that my first used her right hand for most signs (she is right handed) I first thought this was because I signed with my right hand.. however, my second (still signing) uses his left hand to sign.. (my suspicion is that he will be left handed.. I'll have to wait a few years to get that confirmed.)

[Chemistry4me]

Some other random links:

http://www.thenakedscientists.com/forum/index.php?topic=1067.0
http://www.thenakedscientists.com/forum/index.php?topic=4979.0
http://www.thenakedscientists.com/forum/index.php?topic=2412.0
http://www.thenakedscientists.com/forum/index.php?topic=1478.0

[ereader]

I was once told that the crown of the head (shown by the sworl of hair at the back) shows a person's handedness.  Sounds strange but it seems to be so in most cases - I'm left-handed and left-crowned.  I'm also ambidextrous but that is something that I have learned when sewing, ironing, using a hammer or screwdriver etc simply because it is useful to approach things from a different angle very often.  I was glad to hear about the link between hair growth and handedness as it seems to rule out brain damage at birth, which was another explanation I had heard, along with the fact that we are the left-over twin (the opposite one having died early after conception without being missed).  What was that book I heard recommended on NS about left-handedness?