Is right-handedness the result of Darwinian evolution?

It’s said that the left side of the brain is “analytical”. We use it for logical thinking, creating strategies, forming words and languages, etc. The right side is said to be “artistic”. We use it for spatial perception, symbols and images, risk taking, etc. We also know that the left side of the brain controls the right side of the body, and vice versa. Most people are right-handed, so following this logic most people are “left-brained”, right?

It seems to me that a left-brained person would have an advantage in survival situations such as those in which we evolved. An “left-brained” early human might be able, for example, to study the movements of animals and be able to kill them. A “right-brained” early human might get the “big picture” (i.e., he sees an animal and imagines himself eating it), but might have a more difficult time than a “left-brained” early human in bringing his imaginings to fruition. So it seems that a “left-brained” early human would be a better hunter, and would thus be more successful.

If this is true (and I don’t know if it is, which is why I’m asking), would that explain why most people are right-handed?

Since no one knows exactly what causes handedness, it’s impossible to say. What I can tell you is that handedness isn’t anywhere near 100% genetic in origin, based on twin studies.

However, I will say that “left-brain” and “right-brain” stuff is largely crap. Moreover, handedness doesn’t correlate anywhere near perfectly with “hemispheredness”, and even when lefties are right-brain dominant, the mapping of brain functions often follows different patterns. So they might not be “artistic”.

Makes sense to me. Never really thought about it until now, but most left handed people I know do seem to think a bit differently than I do.

Also, a bit of a follow on. When I go to bed, I’ve noticed that if I’m laying on my left side, I start “daydreaming” immediately. Roll to the right, and there isn’t a thought in my head. Back to the left, and my “daydreams” pick up right where I left off. Blood pooling/draining in the brain maybe?

Can you direct one to such studies?

I vaguely remember half hearing a report several years ago that statistic indicated that left-handedness could arise from two independent genes, one recessive, one sex-linked (maybe the same gene was both.

Does anyone remember the details any better?

Off to google

Well, you’re about as likely to find something with google as I am, I guess. But here’s one I dredged up:


Seems reasonable to conclude that pre-natal environment has as much or more to do with it than genetics.

Why didn’t I go straight to Science Friday?

Two brief quotes:
Dr. Amar Klar, a researcher at the genetics laboratories for the National Cancer Center has found that people who inherit a specific gene, from either parent or both, are born right-handed. People who lack the gene altogether have 50/50 odds of being either right- or left-handed. [1997]


They found that all quantitative information was in excellent agreement with a 2-gene, 4-allele model, one locus pertaining to left or right hemispheric dominance and the other to contralateral or ipsilateral hand control relative to the dominant hemisphere.
[three studies too old for me to grant too much creedance; I won’t trust handedness on any one older than I am, as I was encouraged to use my right-hand in school]

Off to read the article, and it’s sources; both my spouse and I are the only know lefties in our families, so I find the subject very interesting.

In what context? Could you clarify this?

A right-brain person would be more likely to come up with group hunting strategies, such as flanking the animal and driving it into an ambush.

This quote is a bit chopped up:

*f left-handedness were less favorable, one would expect the amount of left-handers to decrease over time. This does not appear to be the case. Coren (1992) has addressed issues concerning the evolution of handedness …[he] searched university collections of art books from European, Asian, African, and American sources and found 10,000 works spanning the Stone Age to 1950. It is assumed that the artist tells us the handedness of the people around him or her by the way the objects are placed in the picture. Coren claims there has been the same distribution of right-handers for 50 gener2ations. Additional studies have been done by anthropologists who analyzed tools used by man since the Stone Age. These studies report the same handedness distribution (Coren, 1992).

I always figured when man started using weapons that those who used them in their right hand for some reason, most likely luck, happened to win a few more fights which led to more right-handed fighters. Or perhaps a great right-handed swordsman taught the Roman legions how to fight, and everyone learned right-handed to make it easier to teach, make hand-specific weapons, or line up in more perfect formations if everyone’s using the same hand. Um…no cite on this :slight_smile: