Why is Left-handedness Relatively Uncommon in Human Beings?

[Ingvaeonic]

I recently read, or rather re-read, Martin Gardner's excellent book from the 60s, The Ambidextrous Universe: Left, Right, and the Fall of Parity (1st published in 1964 as The Ambidextrous Universe: Mirror Asymmetry and Time-Reversed Worlds), and this got me thinking as to why left-handedness is comparatively uncommon in human beings and there remains no conclusive answer as to the cause or source of this human phenomenon.

In other mammals and in some species of birds, I have been lead to believe, the preference for one one paw, claw, etc. is evenly distributed between the left and right and in the case of some primates, ambidexterity is the rule and not the exception.

The uncommonness of left-handedness among human beings seems strange and it would seem that this is a characteristic more man-made than naturally occurring.

[MarsOsix]

My intuition would be that as animals who heavily rely on tool use and social cooperation, there would be some sort of selection towards one form of handedness, just on the basis that tools and that sort of thing would be produced with dominant-handed people in mind.

[Ocko]

My guess would be that it has to do which brain half a culture prefers, left brain or right brain.

I recently heart that it has also deeper psychological correlations all the way to ethics.

[Ingvaeonic]

My intuition would be that as animals who heavily rely on tool use and social cooperation, there would be some sort of selection towards one form of handedness, just on the basis that tools and that sort of thing would be produced with dominant-handed people in mind.

Yes, there is that to it. But if predominant right-handedness is a product of the evolutionary process, it must be hereditary. However, it has been hotly disputed by some that handedness is hereditary.

These some very learned and knowledgeable persons have maintained that there is enough good and cogent empirical evidence that right-handedness is more a product of learnt behavior and practice than genetics. Handedness is produced by the primacy of nurture over nature. And if this is so, why the predominance of the right hand over the left hand and not vice versa? We live in a universe that knows neither left nor right, which are useful but purely arbitrary human terms.

And it would make sense from an evolutionary standpoint that ambidexterity rather than predominant right-handedness would have been more useful. Equal strength and dexterity in both hands would make for tasks to be better and more readily accomplished under circumstances that favor one side or the other.

[Ingvaeonic]

My guess would be that it has to do which brain half a culture prefers, left brain or right brain.

I recently heart that it has also deeper psychological correlations all the way to ethics.

Once more, this is an aspect of the argument that handedness, as a product of cultural bias, is a product of learnt behavior and practice. Nurture over nature again.

[Catterick]

My intuition would be that as animals who heavily rely on tool use and social cooperation, there would be some sort of selection towards one form of handedness, just on the basis that tools and that sort of thing would be produced with dominant-handed people in mind.

I remember that in vertebrates laterality goes back at least as far as sharks. Sharks and bony fishes show a preference for one side over the other. In humans brain laterality is particularly developed, and it is thought to have something to do with toolmaking.

[MarsOsix]

I remember that in vertebrates laterality goes back at least as far as sharks. Sharks and bony fishes show a preference for one side over the other. In humans brain laterality is particularly developed, and it is thought to have something to do with toolmaking.

Why might this be the case in vertebrates? I can't imagine there to be an analogue of tool-making, but I guess there would be other factors to select for laterality.

[Catterick]

Why might this be the case in vertebrates? I can't imagine there to be an analogue of tool-making, but I guess there would be other factors to select for laterality.

The theory is genetic variability for handedness in a population helps confuse predators anticipating the movements of prey.