Imagine a group of humans confined in a place of fixed but commodious dimensions, well-tended and wanting for nothing. They have plenty to eat, plenty of water, plenty of places to live, and only the dimmest sort of apprehension of a larger world. They might even think of "the outside" as a kind of malicious fiction perpetrated by malcontents. It's a circumstance not unlike the one "sustainable development" is supposed to create for us. Also, it is not unlike the “universes” of John Calhoun's rats.
Laboratory animals often substitute for humans in tests of hazardous environmental factors. Their use in the study of cancer-causing and toxic chemicals is almost universally accepted. Their responses can, and do, give insight into human behavioral psychology. They are useful as models for humans precisely because their repertoire of behaviors is simpler than that of men and women, and so it is easier for scientists to control the variables. This also gives us the latitude to say, when we don't like the results of such tests, that humans and rats are different.
And that is why, when ecologist John B. Calhoun passed from the scene in September of 1995, The New York Times noted in his obituary that his work had often met with "studied disregard." He had spent his life studying the behavior of enclosed rodents.
The term "enclosure" has a specific meaning different from crowding. Calhoun's animals were not just thrown together in a cage. They grew up in confinement, generation after generation, without the ability to imagine an escape.
The research began at Johns Hopkins in 1946 and continued through the '60s, when Calhoun, then a research psychologist at the National Institute of Mental Health, published a report of the work in Scientific American. What fascinated students and readers of this research, then and now, is that the rats, mice, and voles in Calhoun's experiments developed social pathologies similar to the behavior of humans trapped in cities. Among the males, behavioral disturbances included sexual deviation and cannibalism. Even the most normal males in the group occasionally went berserk, attacking less dominant males, juveniles and females. Failures of reproductive function in the females - the rat equivalence of neglect, abuse and endangerment - were so severe that the colonies would have died out eventually had they been permitted to continue.
Before going on, it is especially important to be clear on this point: None of Calhoun's experiments began with throngs. All of his populations started out small, with superabundant resources, and grew after many generations into a state of crowding that approximated 80% of carrying capacity. That is to say, 80% of the nesting boxes in the enclosures were occupied at the peak population.
Appropriately, Calhoun called his confinements "universes," since the animals inside them knew nothing of an outside. Full details of Universe 25 appear in a 1970 paper titled “The Explosive Growth and Demise of a Mouse Population.”
A few salient points from the paper:
• The mice in Universe 25 developed a social system with a fixed number of places. In nature, the excess population emigrates to what, in human terms, would be a frontier. But in Calhoun's rodent Shangri-La, the possibility of emigration was excluded because ecologists define emigration as a "mortality factor." It is therefore not utopian. Rejected males gathered in "pools" on the floor of the universe, where they fought frequently. Females not accepted in the social structure withdrew to less-preferred nesting boxes in the higher reaches of the universe.
• Dealing with large numbers of maturing competitors overtaxed the territorial males. In response to the invasion of nesting sites by interlopers, females became aggressive, taking over some of the defensive duties of the males. This aggression generalized to their young. A pronounced rise in preweaning mortality marked the end of social structure in Universe 25.
• With the end of successful reproductive activity, the population plunged exponentially and the age distribution shifted into senescence. The remaining individuals of reproductive age had, by this time, lost interest in courting. Calhoun dubbed these males "beautiful ones" for their obsessive grooming.
• It had been expected that the population would rebound after declining to a few remnant groups. It did not. What's more, healthy young individuals from Universe 25, transplanted to an empty universe of their own, failed to develop a social structure or engage in reproductive activity.
It seems clear that, for rodents at least, the absence of frontiers leads to what Calhoun calls "death of the spirit." This first death leads to species extinction, the "second death." A study of the headlines over the last thirty years or so yields some interesting parallels with the human condition, but there's no room for that here.
A final observation: Calhoun's work remains unfinished. His experiments could be extended to include a frontier, or an unlimited succession of frontiers, by linking a populated universe with a string of empty ones. The path to each new universe would have to be made arduous, say by a maze, or by an electrical grid designed to deliver painful but non-fatal shocks. Even more interesting, for computational types, would be the creation of digital life forms complex enough to check out frontier theory analytically.
Those of you readers interested in such things, do try. One might say your life depends on it.
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