[maryz]

What I want to know is what causes left-handedness, and why in such a low percentage?

Nature seems to favor the clock-wise rotation over counter-clockwise.

Actually, I read a few years ago that, as far as they can determine "handedness" among animals, it seems to break down 50-50 between left and right. The discrepancy among humans is anomalous.

[ffusco]

It's probably a cultural thing. For centuries left-handedness was considered "sinister". Lefties are still encouraged to be somewhat ambidextrous, tool makers also favor the right-handed design.