Across human history, societal disruptions have exposed the fault lines of our relationships.

For thousands of years, marriage served mostly a societal function. Aristocrats used it as a tool to consolidate wealth and property across generations. Meanwhile, serfs worked the land for feudal lords, who often controlled their marriages so that couples could be economically viable units.

“It was too vital an economic and political institution to be entered into solely on the basis of something as irrational as love,” writes historian Stephanie Coontz in her book, Marriage, a History.

But after the Black Death killed up to half of Europe’s population in the mid-1300s, there was a massive labor shortage. Serfs were able to take up trades or jobs that were independent of feudal lords, so they had more freedom and incentive to find partners they got along with. “A harmonious, well-functioning marriage was a business necessity as well as a personal pleasure,” Coontz writes.

Eventually in the late 1700s, people started to marry for love. But this gave rise to dogmatic beliefs that men and women have innately different natures—that men are better-suited to occupy public life, while women should gracefully uphold the domestic and moral standards of the home. By the early 1900s, these beliefs coalesced into the ideal that the man should be the sole breadwinner.

In the 1930s, the Great Depression threw a wrench into these expectations when men lost their jobs and women sought out work.

“This threatened the ‘modern’ ideas of masculinity and marriage that most men had come to embrace over the previous two decades,” Coontz writes. “Unemployed men often lost their sense of identity and became demoralized. Many turned to drink. Tempers flared at home.”

Ever since the 1960s, more people have wanted their relationships to be about self-fulfillment. We want our partners to help us be our best selves, rather than playing a societal role. It has freed us from many traditional and often sexist expectations—but we’re also relying more on our relationships than ever before.

“Never before in history had societies thought that such a set of high expectations about marriage was either realistic or desirable,” Coontz writes.