Ah, the girls in their summer dresses.

But why isn’t it the boys in their summer dresses? Why don’t I wear a dress?

This question came to me the other day as I walked downtown, absentmindedly taking in the exposed shoulders and bare legs of the modern American woman. And when my colleague Petula Dvorak blamed the patriarchy for freezing these poor women in the crisper drawer of over-air-conditioned offices, I wondered how we’d arrived here in the first place: men in trousers, women in skirts.

I suppose the main reason I don’t wear a dress is that I’m as susceptible to peer-group pressure as anyone. In a town as conservative as Washington, even wearing a striped shirt can raise eyebrows. But the question remains: Why do women wear dresses and why don’t men?

Is it biological? Is there a deep-seated evolutionary reason whereby natural selection favors a woman whose ankles and elbows are visible to men?

No, said Joanne B. Eicher , regents professor emerita at the University of Minnesota and editor of the 10-volume “Encyclopedia of World Dress and Fashion.”

“Most of us would reject that,” said Eicher, an anthropologist. “I don’t think we would find very many people who say that men, or people who identify as men, or women, or people who identify as women, have some basic DNA that would make them want to wear a dress or wear a suit or cover up this way or that way. There are just too many variations.”

In other words, some cultures favor bikinis. Others favor burqas. Babies seem to be produced in both.

When we’re talking about clothes, we’re really talking about culture. We wear what we’re conditioned to wear by the society around us. In the West, that means men don’t wear dresses. How did we get here?

Let’s start at the beginning, or close to it. In the 1970s, textile historian Dorothy K. Burnham posited that early societies that depended on animal skins for clothing favored what we would call pants. A skinned hide naturally lent itself to that more form-fitting garment — for men and women. (Think Mongolians and Arctic peoples.)

Societies that wove fabric, on the other hand, created robed garments, what we would think of as dresses or skirts. The rectangle of cloth that comes off a loom is easy to fold and drape — on women and men. (Think Scottish kilts and Roman togas.)

For centuries in Europe, men’s and women’s clothing wasn’t all that different. More notable were class differences. Male and female laborers wore shorter skirts. A long robe would interfere with manual tasks. (In some societies, there were also sumptuary laws that regulated consumption. Lower classes weren’t allowed to wear the cool stuff.)

Over time, upper-class men began to adopt the clothing styles of the working class. In what might strike us as a foreshadowing of the rise of women’s hems, men’s skirts rose, revealing the tights underneath. They rose so high that codpieces were necessary. Eventually, tights become trousers.

Admittedly there is much variation in the details of women’s clothing, but by the 16th century, the basic bifurcation was there: Men wore the pants in the family.

If men’s pants were a result of the upper classes borrowing from the lower classes, the uniform of the modern male executive came from the other direction. The suit jacket came from the casual jacket that English gentlemen wore on their estates.

Completing the package was the necktie, a relative of the cravat. The word “cravat” is derived from the French word for “Croat.” It was 17th-century Croatian soldiers who first wrapped narrow strips of cloth around their necks.

The necktie today is about the only way male office workers can allow themselves a little decorative flourish.

“It’s decorative in the sense that it’s not utilitarian,” said Jo Paoletti , an American studies professor at the University of Maryland and a clothing historian. “But it’s still emblematic. It’s still identifying you as a guy and as a man who has a certain type of job. It’s funny that we talk about white-collar jobs and blue-collar jobs. You could talk about tie jobs and no-tie jobs.”

Where there is culture there are culture wars, and what is appropriate dress for different places is constantly argued over.

“There are official dress codes and cultural dress codes,” Paoletti said. “Nobody votes on cultural dress codes. Nobody circulates them. You just know if you’re a guy, you don’t wear Bermuda shorts to the office, unless you’re in Bermuda.”

And you don’t wear a dress.

I’m fine wearing a suit and tie. They make me feel — dare I say it? — like a man. Still, I’m kind of hoping the codpiece makes a comeback.

Twitter: @johnkelly

For previous columns, visit washingtonpost.com/johnkelly.