Button Up

When I was a child I remember the first time someone pointed out that men's and women's shirts buttoned on opposite sides,I wanted to know why and was told at the time it was so you could tell if it was a male or female shirt. Long story short I never did get an answer though I recently came across a few logical guesses. The first conjecture was that since women held their infants mainly on their left it made it easier to unbutton to nurse. Secondly when women still rode side saddle it was also to the left so the buttons lessened the amount of cold air. The third and final guess only applied to those who had servants to help them dress,the buttons would be easier for the help to work with,and the men in those times apparently dressed themselves.