Back in the really early days, the men went out hunting, the women stayed home with the kids, and would hold the kid in one arm against the heart, so that's the left, and with the right arm they would throw. And it turns out you cannot make that calculation in real time. You have to have an algorithm set up. So these brain mechanisms evolved in order to do that, and when they evolved, the thing is that where there is a useful capability it often adapts to places it wasn't evolved for.
