Maybe you've noticed it, maybe you haven't, but one of the primary differences between men and women's button up shirts is that they button up on the opposite side. On shirts, they're on the left for the ladies and on the right for the gents. 

Which made us wonder... why?

Well, the answer is because of horses, babies, and Napoleon.

There are several different theories as to why buttons are gendered on dress shirts. Many of them are interesting, and historically rooted, but none have been deemed labelled definitive.

Theory 1. swords

Men's shirts had buttons on the right side, with the open flap on the left. In the olden days of yore, wealthy men's clothing often included weaponry (I'm waiting for the day when the GAP has a buy 2 get 1 sword free campaign!). Since most people are right-handed, and therefore hold their sword in the right hand (sorry lefties!) it was, according to this Quora thread, "more convenient and quicker to use their left hand for unbuttoning. 

So where's the evidence? Portraiture. Take a look at this dude and you'll notice a pretty popular "hand-in-coat" stance from the 19th century. 

Seen here is a right-button orientation that, according to The Art of Chivalry: European Arms and Armor from the Metropolitan Museum of Art, was designed to "insure that an enemy's lance point would not slip between the plates, they overlapped from left to right, since it was standard fighting practice that the left side, protected by the shield, was turned toward the enemy. Thus, men's jackets button left to right even to the present day."

Well, we've got the men's buttons down, but why are women's buttons on the left?

Theory 2. Babies

Sorry again lefties, this shirt button orientation has really left you in the dust. The position of these buttons was based on the fact that most women (right handed women) hold their infants in their left arms. So putting the open flap on the right made it easier to maneuver their shirt for breastfeeding. 

Theory 3. Horses. 

So you know how in the olden days women, in large part, rode sidesaddle? Putting the shirt and dress buttons on the left hand side reduced gusts of wind from entering the shirt as women trotted along. 

Theory 4. Spite

The time when clothing manufacturing practices were becoming more standardized (aka the early days of industrialization) was also the early days of the women's movement. One theory holds that clothing manufacturers were feeling spiteful, so standardized little things in men and women's clothing that would ever so subtly re-assert a difference between the genders. 

Theory 4. The most reasonable theory

It's pretty well known that during the age of industrialization, when clothing was becoming standardized, wealthy women didn't dress themselves. The buttons are on the other side because it was easier for servants to help rich women get their shirt on if the buttons were mirrored. 

When buttons became easier to manufacture and apply to clothing, opening them up to mass consumption, the buttons remained on the left so the masses could mimic the style of the wealthy. 

Fun fact about this one: The 19th Century sexologist Havelock Ellis tried to use the difference in buttons to argue that women were inferior to men, because men were able to dress themselves. 

So what do you think?