It could be a future diorama at New York’s Museum of Natural History: A human male and female who not only got married, but stayed married.

Divorce among 50-somethings has doubled since 1990. One in five adults have never married, up from one in ten 30 years ago. In all, a majority of American adults are now single, government data show, including the mothers of two out of every five newborns.

These trends are often blamed on feminists or gay rights activists or hippies, who’ve somehow found a way to make Americans reject tradition.

But the last several years showed a different powerful force changing families: the economy.

The effects of the Great Recession on families are hard to ignore. Births and marriages have plunged, as millions of millennials skip or delay starting traditional families. The economic uncertainty of the downturn dismantled job security which, in turned, ripped up many wedding plans.

Families that have made unconventional arrangements are the most financially fragile. An Allianz survey of 4,500 Americans included an extra sample of families outside the historical norm, including single parents, same-sex couples and blended families. These “modern families” were less financially secure than traditional families, the study found. They were 50 percent more likely to have unexpectedly lost their main form of income -- and twice as likely to have declared bankruptcy.

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Rocky times rearrange plans and priorities. When women in their early 20’s face an economy with high unemployment, for example, they tend to have fewer children. The spike in unemployment starting in 2008 should result in 9.2 million young women giving birth to 430,000 fewer babies over their lifetimes, according to a 2014 National Academy of Science study.

Why would more unemployment mean fewer babies? When asked what they’d like in a potential spouse, single men’s top answer is “similar ideas about having and raising children,” a Pew Research survey found in September. But when women were asked, 78 percent said they wanted a spouse with “a steady job.”

A man with a steady job is harder to find. Since the 1970s, men have been holding jobs for shorter and shorter periods of time. Women’s average job tenure hasn’t fallen, but that’s only because so many more joined the workforce in the ‘80s and ‘90s. Both sexes are working more temporary or contract gigs, have stagnant wages and enjoy fewer company benefits. The number of big companies offering pensions has dropped 57 percent in 10 years. Even good-paying jobs are more demanding and more likely to end in layoffs or buyouts. Meanwhile, the cost of raising a kid is up 24 percent in inflation-adjusted dollars since 1960, the Department of Agriculture estimates, to $245,340.

While single women find it harder to find men they want to marry, existing families feel the strain of what University of Virginia sociologist Allison Pugh calls “the age of insecurity.” Job insecurity causes anxiety and depression and, a 2012 study shows, makes fathers less supportive of their kids. Women in areas hardest hit by the recession report more “controlling behavior” by boyfriends and husbands, University of California, Berkeley sociologist Daniel Schneider says. When most Americans talk about their jobs and families, they sound stressed and frantic, Pugh’s research finds. “Job insecurity destabilizes our assumptions about what we owe each other at work and at home,” she says.

Affluent, college-educated people can afford to shrug off much of this insecurity. Their jobs aren’t exactly safe, but if they’re laid off they have a good chance of getting a new one. The jobless rate for college grads is 3.1 percent, about half the overall rate. The attitudes of the affluent best match those of union members with steady jobs, Pugh says. Both groups are full of “low-key pragmatism” about jobs and relationships, not feelings of panic or betrayal.

That explains why families of both union members and college-educated professionals still look pretty traditional. The 14-year-old daughter of college graduates is actually more likely now than in the 1970s to be living with parents who have remained married to each other.

If economic stress leads to more unconventional relationships, will an economic recovery send more couples down the traditional aisle? The most recent data suggest the marriage rate stopped its slide as the economy rebounded. Unfortunately, the number of divorces is also on the upswing. A better economy makes it easier to get hitched, but also easier to go through with divorces postponed during the recession. Wedding venues and divorce lawyers aren’t cheap.

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