Why aren't more people left-handed?

My great-grandfather was left-handed. He had five children and wanted one of them to be left-handed, too. I am the first member of the family that is left-handed and I am four generations away. I did a quick Google search and determined that about 13% of the general population are left-handed. Once upon a time I worked in quality control and was familiar with some industrial statistics but my feeble familiarity with probability theory is way past. It seems to me that given three possible outcomes: right-handed, left-handed, and ambidextrious with ambidextrious being, rare exception, a larger percentage of the population should be left-handed. What gives? Any statisticians or geneticists among the teeming millions?

Just because there’s an even probability of result x or result y in a given situation, it does not necessarily follow that the result of a large number of such situations will turn out 50-50. The dominance of right-handedness is by chance. It’s the same as in England, there are far more people called Smith than called Wright, despite there being similar numbers of blacksmiths and wheelwrights (ie one in each village) at the time when surnames became common.

Perhaps there’s an alternate theory about the dominance of the left half of the brain and it’s control of the right hand, in which case I’d love to hear it.

If there is a preponderance of X or Y in a very large population then there isn’t an even probability. If the probability was 50/50 we’d see some variation but certainly not an overwhelming right hand bias in virtually ever sample as well as the whole world’s population. I think it may be more meaningful to say that just because the choices are binary doesn’t mean there is an equal probability of each outcome.

I hit enter a bit too soon before adding my cite.

My wife, TheLadyLion (who has a masters in developmental psych), informs me that the dominant hand is related to the speech center of the brain which is normally in the left hemisphere for about 90% of the population.

A lot of people who are “ambidextrious” account for your missing lefties. While lefties are in the minority even as toddlers, there are a lot more of them than the 11-14% precent you end up with as adults. Many studies put the figure at close to 1/3rd of toddlers showing left-hand preference.

The problem is, until fairly recently (and even today to a lesser extent) being left-handed was seen as something kids could be “cured” of if they weren’t allowed to use their dominent hand. So there are a lot of people like my mother who, because she was forced to write with her right hand in school, are equally “good” with either hand - an ambidextriousness of a sort. You’d swear she should have been a doctor from her writing. :mad: I’m only 26, but even I had a 1st grade teacher who tried to make me write with my right hand (but fortunately there was no knuckle beating or tying of my hand like mom’s nuns did to her as a kid) so people aren’t terribly enlighten yet; and it’s worse for lefties in other parts of the world.

As for why there are less of us born left-handed in the first place, it’s a miracle that we survive childhood at all given that the majority of objects and machines are designed for the use of the opposite hand :smiley:

An evolutionary/anthropological view, to add to Padeye’s post:

Leakey, Richard. The Origin of Humankind, © 1994, pp. 128-130

There’s a proud educational tradition–especially in Catholic schools–of treating left-handedness as some kind of willful deviant behavior, correctable with a modicum of discipline, like nailbiting or nosepicking. My nephew, a grade-schooler in the early 90s, was actually told “No, Louie, we write with our right hand!” In his recounting of the story, he added “So I left with my left hand!”

There are four possibilities: left, right, both, none. Some people are born without hands.

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It seems unlikely to me that there would be equal numbers. Blacksmiths spend a fair amount of their time in shoeing horses, and that needs to be re-done very few months. Wheelwrights produce wheels, but once made they typically last for years. Plus there were many horses of that time used exclusively for riding or farm work, not pulling wheeled vehicles. So those horses needed shoes, but not wheels. Thus it seems likely that the average village needed more blacksmiths than wheelwrights.

Also, blacksmiths are not the only ones who ended up with the name of “Smith”. There were also whitesmiths (tinsmiths/pot menders), goldsmiths & silversmiths (jewlers), coppersmiths, bronzesmiths, and even locksmiths.

(An alternative to the name “Smith”, they often ended up with the metal/color name, thus “Black”, “White”, “Gold”, “Locke”, etc.)

What’s “left-handed” and “right-handed” exactly?

I know the rule of the thumb is that if you write with your left, you are a left-hander. But what if (for me, for example), I write with my right, but do a lot of other things with my left? eg using a pair of scissors, or with utensils like forks and knives (if presented with just one of them I will instinctively hold them with my left).

So how do you define left and right handedness?

I write with my left hand. Teachers tried to force me to change but it just felt “wrong” to write with my right hand so I never did.

hmmmm…Interesting question. What defines if you are a “true” lefty or not.
I write, eat, etc with my left hand. It just seems natural.

However, I use my right hand for; the mouse, I shoot right handed, and I play guitar right handed.