Left-Handedness

The most common explanation for why some people are left-handed is that it has to do with how the right and left halves of the brain function differently. Yet, research has shown that it is unrelated to the brain in any way. Even with genetics, we still lack a solid means to anticipate whether someone will end up being left or right-handed since the spinal cord makes this decision long before the brain has fully formed inside the womb.

Then there is the mystery of why roughly 90% of people are right-handed, which would seem to have a fairly even distribution. As things stand, it's another one of those puzzles that, despite our constantly expanding collection of scientific tools, we've known about for a while but haven't been able to solve.

Also, it has an evolutionary and social component. Being left-handed is unquestionably a disadvantage because everything appears to be made with right-handers in mind. Moreover, left-handedness has historically been associated with evil in many cultures around the world; in fact, the word "sinister" is derived from a latin term that means "on the left side." If the trait was hereditary, it should already have been eliminated from the population by now, but we lack solid studies to definitively verify that it is.