New research at the University of Illinois examined data on nearly 1,500 men and 1,800 women between the ages of 52 and 60 and found that couples who resist traditional gender roles, or who shoot for a so-called equal marriage, are less happy than those who swim with the tide.

Researchers Karen Kramer and Sunjin Pak found that when women’s paychecks increased, they reported more symptoms of depression. But the opposite effect was found in men: their psychological well-being was highest when they were the primary wage-earners.

“We observed a statistically significant and substantial difference in depressive symptoms between men and women in our study,” said Kramer. “The results supported the overarching hypothesis: well-being was lower for mothers and fathers who violated gendered expectations about the division of paid labor, and higher for parents who conformed to these expectations.”

This was true even for couples who had an egalitarian view of work and family. Modern views notwithstanding, men’s health took a hit when their earnings shrank—clearly suggesting the traditional role of primary earner is still very important to men.

While these findings aren’t surprising to many of us, they certainly defy the cultural narrative. Americans are forever being told that “gender equality”— which is no longer defined as equal opportunity but as male and female interchangeability—is the only road to a happy life.

If happiness is not the result, well, that’s society’s fault. Our expectations about gender roles have been slower to evolve, some say. “Men and women who deviate from 'conventional gender roles' — especially fathers who leave work to care for children full time — may be perceived negatively, which in turn can affect their mental health,” writes Claudia Tanner, at MailOnline.

That’s not it.

Men and women are not interchangeable beings, pure and simple. They may both be capable of being breadwinners and full-time parents, but that doesn’t mean they want to perform these tasks with equal fervor. Typically speaking, a man’s identity is inextricably linked to his paycheck. A woman’s is linked to her children. That this does not hold true for every woman and every man doesn’t change the fact that what drives most women is different from what drives most men.

Giving birth is a woman’s unparalleled accomplishment—her first instinct is to provide for that child physically and emotionally. A man’s first instinct is to protect and to provide for that child. That’s his unparalleled accomplishment.

It’s time to stop pretending the culture is to blame for why “equal marriages” backfire. (I use the term “equal marriages” reluctantly, since an equal marriage has nothing to do with who performs which tasks inside and outside the home.) Human nature doesn’t change just because society does. Just as women are emotionally invested in the home in a unique and primal way, men have a visceral need to provide and protect. That’s how most men and women gain their sense of self-worth.

That is not to say no married couple can successfully navigate a role reversal. It is only to say that it’s rare. Even today, approximately 30 percent of married women with children choose not to be employed— and in families where both parents are employed, “70 percent consist of fathers who earn more than mothers.”

That’s because it’s natural for a woman to want to depend on her man, and it is not natural for a man to depend on a woman. No matter how hard that is to hear, or how politically incorrect it may be, it still stands.

The research from the University of Illinois (and for the record, it’s not the only research with similar findings: try here and here and here) is clear: When females were the main breadwinner in the family, they reported more symptoms of depression; but men’s psychological well-being was highest when they were the primary wage-earners.

Societal attitudes may have changed, but human nature has not. Perhaps it’s time we surrendered.