This question has probably been asked a million times on here, but I’m going to ask it again anyway 
. Why are the large majority of people right-handed, and what are the causes of right-handedness to be favored over left-handedness?
I think the thing here is sheer habit. Most people are right handed so they train their kids to be the same. I don’t think right-handedness is favored but most objects are made for the typical right handed consumer in mind. Now, how the masses of people started out using that hand a majority of the time, I don’t know… It was a fifty fifty chance with that one.
I don’t have my old sociology book with me, so I can’t remember the exact culture, but I do know that some middle eastern cultures tend to wipe their ass with their left(or is it right?) hand, and eat with their right (or is it left?). This was under a section about culture shock and the point was that someone from this culture would be appalled to see you eating with your left(?) hand.
Here’s some info. Hope it helps.
My daughter is a lefty. We never “trained” her to be any specific way. Determining her handedness was one of the few times I followed what the baby book said to do, and that was simply place objects in front of her, and let her use whichever hand she was more comfortable with. By the time she was about a year old, it was obvious she was a lefty.
Muslims are taught to always eat with the right and wipe with the left. There is a lack of water in the desert, obviously, so they learned this for hygiene reasons. There is a rule for wiping one’s backside with a stone which gave instructions on which direction to turn the stone one used and how to place it on the ground afterward. I read that in an hilarious book called ‘The REsearch Guide to Bodily Fluids’. I’m sure they are past this line of reasoning now, but it is still considered gauche to shake hands with the left. I seem to recall a news story a few years back about a reporter who photographed a prominent person in the Arab world shaking hands with the left and was jailed a few days for publishing the pic.
I saw a fascinating documentary about identical twins a few years ago in which they stated nearly 80% of all pregnancies begin as identical twins, but one of them is lost before the mother even know she is pregnant. They also said if the egg splits right away, you have identical twins, if it splits after perhaps ten days, you have twins that are a mirror image of eachother, eg., one will have a protuding incisor tooth on the right side, the other on the left. One will be right handed, the other left handed. They surmise with a left handed person, they were born an identical twin where the egg didn’t split right away, and the other twin didn’t make it.
Source: http://duke.usask.ca/~elias/left/
<hijack>
You forget that everyone is born left-handed. You turn right-handed when you commit your first sin.
</hijack>
Duckster <----- No sins!
Indeed, the left hand has always been considered to be, for whatever reason, the “bad” hand. Consider the Latin words for left and right: sinister and dexter, respectively. Hence the root for the English word sinister.
As far as the genetic basis for left or right-handedness, I heard somewhere that it can have a great deal to do with the direction that the sperm swim when attached to the egg (seriously). Apparently even after fertilization the sperm stay attached to the egg and “swim” in place, not actually going anywhere but keeping nutrients flowing across the developing zygote. I don’t remember where I read this though…
zkitcab, Duckster–
For what it’s worth, my family seems to be a case where genetics rather than learning determined handedness. I remember spending much more time around my right-handed father than my left-handed mother as a child, and he was the one mostly responsible for teaching me how to write/throw/etc–but even then I was already an obvious lefty like Mom. My sister, on the other hand, was being raised entirely by my mother when she finally stopped being ambidextrous (around kindergarten) and became right-handed.
Two cases prove nothing, I know, but figured it was worth a mention.
P.S. Is it true that you can tell whether a left-handed person has his entire brain hemispheres or just his motor centers “switched” by watching how he holds a pencil?
There are whole raftloads of theories about what makes people left and right handed. Most of the ones with any plausibility centre on pre-natal environment.
It’s not taught. It’s not habit.
But the genetic component doesn’t seem to be very large, either.
The leading theories, as I recall, have to do with such things as hormone levels and fetal position during pregnancy. I’ve heard the twin theory, but if I recall correctly it isn’t very strongly supported by the evidence.