The Rodent inside Me

The large majority of my friends, ranging from millennials to seniors, are single whether never-married, divorced, or widowed. Not all, but most. Some of the reason is probably the tendency for married people to hang out with other married people and thereby select themselves out of the mix, but that doesn’t account for all of it. A lot of the reason is simply that there are more single adults than there used to be.

When I was a kid, nearly all of my parents’ friends at picnics and parties were married. I use the word “nearly” because there might have been an exception, but right now I can’t think of one. I didn’t think much about it back then. Marriage just seemed to be something that happened to adults like dry skin and worsening vision: as inevitable as birthdays themselves. This wasn’t true, of course. There always have been advocates for and practitioners of the single life in all times and places. Note the 1942 Kay Kyser hit Jingle Jangle Jingle. A century earlier Charles Darwin waveringly contemplated the costs and benefits of marriage, weighing "terrible loss of time" and "less money for books" against a "constant companion and a friend in old age ... better than a dog anyhow." (Charles decided against the dog and married his cousin Emma.) In 1872 Victoria Woodhull ran for President of the United States in part on an anti-marriage Free Love platform: “to change that love every day if I please, and with that right neither you nor any law you can frame have any right to interfere." (This wasn’t a vote-winner in 1872.) Sumerian proverb etched in a 4000-year-old clay tablet: “Marriage for pleasure, divorce to regain it.” In the 20 years after World War 2, however, it was as close to being true as it ever has been before or since.

The current median age for first marriage (for those who get married at all) is 29 for men and 28 for women. In 1960 the median age for first marriage in the U.S. was 22 for men and 20 for women, meaning almost half the brides were teenagers. In 1960 72% of those between 18 and 35 years old were married with the bulk of the singles at the lowest end of that range. Today according to the Pew Research Center 61% of Americans 18 to 35 are “unpartnered”; the study includes unmarried couples as “partnered,” which means most younger people don’t become couples with or without the formality of marriage. Many never will. For the first time since records have been kept a majority of all adults are single. There is one segment of the population that so far still features ample ambulation down the aisle: marriage rates are holding up surprisingly well for those in the top 20% income level – the group that dominates the culture and the traditional media. They have fallen off a cliff for everyone else. The birth rate is way down, too. In the top 20% income level the majority of births are still to married couples. In the rest of the population they are not, but across the board the fertility rate is down to 1.7. The replacement rate is 2.1, so the population would decline were it not for immigration. In several of the advanced nations in Europe and Asia the populations are already declining. (Global population continues to rise however with the poorest nations growing the fastest.)

There are endless articles on the subject in newspapers, popular magazines, journals, and publications such as Psychology Today. Predictably, most contain spin for one side or other of the gender war, which, like all aspects of life that are remotely political, has grown more choleric in recent years. Authors with opposite spins (overwhelmingly members of that upper 20% either way, one must remember) tend to agree the fading of marriage is a problem however. I’m not so sure that it is. Single parenthood is extra hard to be sure both for the parent and the child, but that is a separate issue from singlehood per se.

The numbers do, however, bring to mind a series of experiments that got quite a bit of news coverage and commentary when I was in high school and college. Every now and then a spate of articles still will appear about them, but they don’t get the traction they did 50 years ago when folks worried more about overpopulation than they do today, even though there are 120,000,000 more people in the U.S. now than there were then.

Dr. John Bumpass Calhoun of the NIH originally studied rats for insights about rodent control in cities, but his studies eventually led him in a different direction. In 1947 his efforts to breed rats on a quarter acre seemed to hit a natural limit when the population hit 150. Despite plentiful food and ideal living conditions they started acting strangely and stopped breeding after reaching that number. Repeating the experiment produced the same result. With support from the NIMH (National Institute of Mental Health) in the 1950s he built ever larger and more elaborate rat utopias, again with the same result: the population would soar, level off at well below an enclosure’s capacity, and then crash despite abundant food and resources for the rats. Shortly before and during the crash, the rodents exhibited bizarre and unsocial behaviors, which he dubbed a behavioral sink. In the 1960s he switched from rats to mice for practical reasons including their smaller size and short life cycles (they live about 2 years and can have 10 litters per year), but the results were the same as with the rats.

Universe 25

The most elaborate mouse facility was “Universe 25” in 1968: a mouse utopia abounding with tunnels, nests, and nesting materials. There were ideal temperatures, plentiful food for all, and no predators. Universe 25 should have been able to accommodate 3000 mice easily, but it never got there. From a handful of breeding pairs the population doubled every 55 days in the “exploit period” until it reached 620 on day 315. The birthrate then began a long decline though at this point it still exceeded the replacement rate. Apparently stressed by the inescapable presence of other mice (again, there was no shortage of food or resources), the mice acted ever more oddly as the population grew. They crowded in some nests while leaving others nearly empty. The females grew aggressive (even toward their own young) while the males became either passive or violent. There were bursts of hypersexuality. By day 560 a generation of mice that hadn’t experienced normal murine upbringing showed diminished interest in mating, competing, or raising young. A few showed enough energy to take possession of some upper nests (mouse penthouses) exclusively for themselves and a few of their favorites – Calhoun dubbed them the “beautiful ones” – but they didn’t reproduce much and avoided interactions with the common mice. Population peaked at 2,200 on day 920. Mouse social behavior by then had become weirdly detached for the most part, but there were outbursts of extreme violence unrelated to the usual competition for status and mates. There even was occasional cannibalism. The birthrate plunged below replacement level and the population began to fall. The birthrate kept falling even when population dropped back below 620; once the social decay set in, it was irreversible. The last baby mouse was born in 1973. The remaining population grew old and died to the last mouse. Every similar experiment ended exactly the same way with 100% mortality.

Calhoun wasn’t shy about suggesting parallels to human societies. To the rejoinder that we aren’t mice, he would answer that in many ways we kind-of are. (See Death Squared: The Explosive Growth and Demise of a Mouse Population [1973] by John Calhoun, which begins “I shall largely speak of mice, but my thoughts are on man.”) However we rationalize our behavior with ideology and philosophy, he suggests, our responses actually may be rooted in biology as much as they are for the rodents. In addition to just the stresses of crowding, he comments, part of the problem for the rodents was precisely the lack of struggle for resources that keeps urban street rats in their brutal environments socially healthy and relentlessly fecund.

Was he right? If so, are the resource-rich nations on day 315 or even 920? I don’t know. But I’m happy being a childless single even if that’s a rationalization and even though I don’t qualify as a “beautiful one” in a penthouse.

Maria Muldaur – Ain’t Gonna Marry