John B Calhoun, scientist

Smithsonian write up

In July 1968, four pairs of mice were introduced into the habitat. There was no shortage of food or water or nesting material. There were no predators. The only adversity was the limit on space.

quote:
Initially, the population grew rapidly, doubling every 55 days. The population reached 620 by day 315, after which the population growth dropped markedly, doubling only every 145 days. The last surviving birth was on day 600, bringing the total population to a mere 2200 mice, even though the experiment setup allowed for as many as 3840 mice in terms of nesting space. This period between day 315 and day 600 saw a breakdown in social structure and in normal social behavior. Among the aberrations in behavior were the following: expulsion of young before weaning was complete, wounding of young, inability of dominant males to maintain the defense of their territory and females, aggressive behavior of females, passivity of non-dominant males with increased attacks on each other which were not defended against.

quote:
At the peak population, most mice spent every living second in the company of hundreds of other mice. They gathered in the main squares, waiting to be fed and occasionally attacking each other. Few females carried pregnancies to term, and the ones that did seemed to simply forget about their babies. They’d move half their litter away from danger and forget the rest. Sometimes they’d drop and abandon a baby while they were carrying it.

The few secluded spaces housed a population Calhoun called, “the beautiful ones.” Generally guarded by one male, the females—and few males—inside the space didn’t breed or fight or do anything but eat and groom and sleep. When the population started declining the beautiful ones were spared from violence and death, but had completely lost touch with social behaviors, including having sex or caring for their young.

Sound familiar?

quote:
After day 600, the social breakdown continued and the population declined toward extinction. During this period females ceased to reproduce. Their male counterparts withdrew completely, never engaging in courtship or fighting and only engaging in tasks that were essential to their health. They ate, drank, slept, and groomed themselves – all solitary pursuits. Sleek, healthy coats and an absence of scars characterized these males. They were dubbed "the beautiful ones." Breeding never resumed and behavior patterns were permanently changed.

The conclusions drawn from this experiment were that when all available space is taken and all social roles filled, competition and the stresses experienced by the individuals will result in a total breakdown in complex social behaviors, ultimately resulting in the demise of the population.

A new conclusion came though, years after the fact, from more liberal scientists.

quote:
Inglis-Arkell explains that the habitats he created weren’t really overcrowded, but that isolation enabled aggressive mice to stake out territory and isolate the beautiful ones. She writes, “Instead of a population problem, one could argue that Universe 25 had a fair distribution problem.”

So you see? The isolated, 'beautiful ones', that didn't have sex, kids, or any normal social interaction were actually just the mice 1%.

A lot of parallels to be drawn here.