Only a right-hander would have to ask such questions. Us true Lefties not already know the answers but knew you were going to ask the questions in the first place. We tolerate this Ad nauseam because it amuses us. 
BTW, it has nothing to do with the physical position of the heart.
At least as late as the 1980s, I met people who thought that I should force my left handed daughter to write and eat with her right hand. I refused to this. She learned to use scissors and a mouse right handed, even though I bought her lefty scissors.
My maternal grandfather was left handed, and the teachers (regular public school teachers) tied his left arm to his body in school, so he sort of learned how to write with his right hand. Then he broke his right arm, and they had to let him write with his left hand. He always claimed that this was why his handwriting was so bad.
You ‘handed’ people amuse us ambis even more. I’ll take on any of you ‘handed’ people, any time. Magic markers at twenty paces. The winner is the first who can write a number ‘6’ top-side up, and proper right-left orientation on the other’s right and left cheeks wins. :p:p:p
What could possibly make them think this was a good idea?
President Garfield was.
He could write in Greek with one hand, and in Latin with the other hand, at the same time!
Because in ye olden days no one believed in a genetic preference for handedness, and since righties were the majority, all kids were forced into learning to write with their right hand.
It sounds quite bizarre; in fact it sounds like how we treated sexual preference until very recently.
Wow. I’d never connected the two before, but that’s exactly what it is. “You can’t favour your left hand! That’s not moral or correct. You must favour your right hand! I’ll teach you to be right-handed!”
As to the question “why handedness?”, I would argue, based on my own personal experience, that handedness confers a definite evolutionary advantage.
I’m right handed, but cross-dominant - that is, for certain things, I prefer my left hand.
The problem is, that requires increased decision-making time.
When I’m cooking, the cross-dominant really comes out - there’s a lot of things where I have to stop and think which hand to use, or I have to experiment to see which is better. For instance, when I’m peeling carrots, it just feels better to hold the carrot in my right hand, and use the peeler in my left. But then it’s time to cut the carrots, and it just feels better to hold the carrot in my left hand, and use the right hand to hold the knife.
So what? Well, lat’s think about caveman Piper and his buddy Thag. Thag sees a saber-toothed tiger coming and, being strongly handed, grabs his spear with his favoured hand to defend himself.
Caveman Piper pauses and thinks, “Hmm, spear against sabre-tooth. Righthand or left hand? Which feels better? Let me experiment …”
Sabre-tooth tiger: “hmm - one guy with a pointy stick at the ready; one guy switching it back and forth … Ka-runch!”
Similarly, I have trouble telling my right from my left - something that other cross-dominants on this board have mentioned in previous threads.
So when I’m driving and Mrs Piper says “Turn left”, and I think, “left - which is left again?” I just sail through the intersection.
So what? Well, when Thag yells, “Caveman Piper - sabre-tooth on your left!”
And Caveman Piper thinks, “left - which I left, again?”
And sabre-tooth again thinks, “one guy with a pointy stick aimed at me, another guy looking at his hands: Ka-runch!”
Ya but that doesn’t explain why left handed people are so underrepresented; it may explain why pseudo-ambidextrous people who suffer from a moment’s confusion are though.
This correlates with homosexuality rates, doesn’t it? Hey, I’m no expert and I’m not drawing conclusions, but it seems to me that there must be, and always have been, genetic predispositions involved in both of these somewhat abnormal conditions.
I wasn’t saying it was. As the opening line of my post indicates, I was just commenting on “why handedness?”, not why there is a general preference for a particular hand.
It might be that right-handedness doesn’t confer any evoluntionary advantage, but rather it’s genetically linked to a trait that does.
There’s research showing that both left-handed and ambidextrous people tend to have certain neurological abnormalities than the right-handed. Autism, schizophrenia, dyslexia, and ADHD are disproportionately represented among left-handers. Both geniuses and mentally handicapped people are also more likely to be left-handed.
The left hemisphere is where most people base their language functioning, both right and left-handed people. But for some reason left-handed people are more likely to have less lateralization, which may make them more physically clumsy and less “smooth tongued”. It’s no surprise that the athletic eloquent fellow is more likely to pass on his genes than the stammering klutz.
So it’s probably not that right-handedness is so desirable that it alone wins the evolutionary contest. It’s just that it’s a sign that, for whatever reason, the brain is laid out in a “desirable” way. But as humans become more reliant on technology, the more “geeky” traits associated with left-handed people may give people more “fitness”. And the nerds shall inherit the earth.
That was pretty much it. Lefthandedness was also linked to being evil in general, and a sign that a person was wicked. A child with a strong preference for using his/her left hand was considered to be headstrong and disobedient at the very least, and my old boss thought that being lefthanded led to devil worship. Of course, she also thought a lot of other things led to devil worship. If she’d known that I had not one but TWO black cats when she’d interviewed me, I never would have been hired.
Handedness is one byproduct of brain lateralization. We still don’t really know why lateralization became prevalent, but it seems to confer some advantages for separate processing. One reason why lefties are supposed to be more creative is that they tend to have less strongly lateralized brains, so they come up with connections between disparate ideas more easily. High intelligence also seems to be lightly correlated with left-handedness.
There’s a pretty good chunk of The Language Instinct and How the Mind Works, both by Steven Pinker, that discuss lateralization, particularly the connection with language. Those are probably the most approachable, yet scientific books I’ve read on the subject.
Handedness is actually a continuum, with few people being totally right- or left-dominant. Some degree of mixed body dominance is common. You might have someone who is strongly right-handed, but strongly left-eyed and weakly left-footed, like a friend of mine I taught to shoot better. You should shoot based on eye dominance, not hand dominance; target acquisition and aiming are the most important things. It took some work to get him using his left hand, but his accuracy and speed went way up afterward.
While there is no single “left handed” gene, there are some genetic factors; handedness can run in families. But environment seems to be a stronger selector. Stressful conditions at conception and birth have an effect on the prevalence of left-handedness.
Actually, violence selects for more lefties. In other words, the minority preference confers an advantage in combat. Either that, or left handed people are naturally more violent 
(Full disclosure: I’m left handed. You got a problem with that?!)
From some of my anthropology reading I remember that the Yanomami have something like 20% incidence of left-handedness. “Fierce” men, who go on more raids and are more willing to undergo inter-tribal duels, have more wives than men who show less aggression, and these men are more likely to be left handed. (In duels they beat each other over the head with really long wooden poles, deliberately receiving head wounds to show how tough they are; this is not dissimilar to Heidelberg dueling).
No—that isn’t what **jtur88 **meant. For observers in the Northern Hemisphere, due to the Earth’s rotation, you see the Sun, Moon, and all the planets and stars going around the sky from left to right, regardless of which direction you’re facing.
Face south, and you’ll see the Sun (and everything else up there) rising on your left hand and setting on your right hand, moving from left to right in front of you.
Face north, and the Sun rises on your right hand and sets on your left hand, going behind you where you can’t see it. If you face north at the summer solstice, you’ll be able to observe the sunrise in the northeast and sunset in the northwest, and from what you can see of it facing north and turning your gaze toward northeast at sunrise and northwest at sunset, relative to the azimuth of your line of sight, it still goes left to right.
In the Northern Hemisphere, the only way to see things going from right to left would be if you had an extra pair of eyes in the back of your head, while still perceiving your left and right hands from the viewpoint of your eyes in the front of your head.
There are three questions here, not one. First, why do individuals have handedness? That’s fairly easy: It’s because being really good with one hand and lousy with the other is usually more useful than being sort of good with both. Northern Piper illustrates this well.
Second, why does handedness tend to be uniform within a species? The use of tools in humans may well be part of it, and humans do seem to have a larger bias than most animals, but many non-tool-using animals also seem to have a species-wide predisposition to one side, so there must be some reason for that.
Third, given a species-wide predisposition to one side or the other, why does a particular species have the predisposition it does? That one is probably just down to random chance.
About 90% of the inhabitable land mass of the earth, and 90% of its zoofauna, occupy the northern hemisphere and look south at the sun and see it go from left to right. As for reading maps, I’m quite certain that genetic handedness predated the convention of placing north at the tops of maps.
Sure, so tell me: What is undesirable about being left-handed? Why would lefties be naturally selected out of the gene pool? They wouldn’t.
They would if they were surrounded by righties, who made and used tools that were awkward for a leftie to use. Or if their righty brethren decided that the minority must be religiously persecuted. Or if there’s some factor external to humanity (the course of the Sun through the sky?) that somehow inherently disfavors lefties.
Unconvincing.