As I understand, about ten percent of the population is left-handed. I would expect the correct explanation to include a reason why the number is close to ten percent.
I have my own theory. When I was a teenager, I visited a chiropracter and he told me that my left leg was one-quarter inch longer than my right leg. Anyone can tell if one leg is longer than the other by sitting on the floor with your back to the wall and extending both legs straight ahead. It’s immediately evident whether one leg is longer and if so, how much.
My theory is that when one leg is significantly (key word here is “significantly”) longer than the other, it establishes a different kind of gait when people walk than it would if both legs were about the same length.
I say “significant” is important because my guess is there is a number (let’s say it one-quarter inch) and if the left leg is longer than the right by one-quarter inch or more, that is enough to cause the propensity towards left-handedness. But if it’s not longer than that number, the leg is not long enough to cause left-handedness.
I suppose one way to try and prove this theory is to study people who were born without the use of their legs. My guess is almost none of them would be left-handed because there is a strong pressure from parents and teachers to force children to use their right hands.
I have no idea whether this theory is correct. Probably not. But I’d be interested to ask what other people think. Does anyone else have a theory?