Don't read this if you're inclined to worry about the future

In 1968 an expert on animal behaviour, John Calhoun, started an experiment.  He built a utopia for mice, designed to satisfy every need.

Even though inhabitants of his mouse utopia had everything needed for an easy life, in less than 2 years the entire population was dead. So what happened?

Calhoun had performed several similar experiments with rodents starting back in the 1940’s.  In each case the population either stalled or turned on itself.  For example, in one experiment Calhoun built an enclosure that should have comfortably housed 5000 rats, but the eventual population never rose above 200 despite unlimited food, water and an absence of predators.

Calhoun noticed that despite ample space, his rodents would often crowd together, which seemed to disrupt their social structure. This unusual phenomenon led Calhoun to conclude that any overpopulated society would inevitably collapse.

His results caught the eye of the National Institute of Mental Health.  The institute was interested in whether the effects Calhoun had observed were due to overpopulation or to some undiscovered factor, and whether would human society might exhibit the same effects.  So NIMH gave Calhoun a grant to repeat his experiment, this time with mice.

Based on his earlier experiments, Calhoun built an enclosure that should have been able to support 3800 mice.  With food and water always plentiful, for ten months all was well: the initial population of eight super-healthy mice grew to 620.

But on day 315 things started to change.  First there was a noticeable drop in population growth.  Initially the population had doubled every 55 days, but after day 315 the doubling time grew to 145 days.  This seemed unusual as the enclosure still had room to comfortably house 3000 more mice.

Calhoun also noticed a marked change in the behavior of both males and females.  Although males had no reason to defend territory or food source--since both were plentiful--they began to form bands or gangs that would randomly attack one another for no apparent reason.  Females began abandoning their young or even attacking them.  And slowly but surely, the mice stopped breeding.

Some of the males began trying to mate with other males.  Some even began to kill other mice, despite the abundance of other food.  And mice began crowding together in groups of 50 or more in pens designed to hold 15, while pens inches away, with plentiful bedding, sat empty.  It didn't make sense.

Most intriguing, a small group of males and females withdrew from the rest altogether.  These mice stopped interacting with others, and had no interest in mating.

The last birth occurred on day 600, and after that the population slowly declined.  But even after the population dropped to levels where the colony had previously flourished, the mice refused to breed or interact.  A few months later the last mouse died.  

Calhoun noted that although the population had survived for many months after day 315, he felt that for all practical purposes it had effectively died on that day-- the day he believed the social bonds had broken down.  Later he wrote “Their spirit has died. They are no longer capable of executing the more complex behaviors compatible with species survival.”

Maybe it's just me, but I see a lot of very disturbing similarities between Calhoun's mice and humans today.  The number of murders (and worse) by druggies or insane perps seems to be skyrocketing.  You just don't hear about 'em unless they're within the coverage area of your local TV station. 

"When a place gets crowded enough to require ID's, social collapse is not far away. --Robert Heinlein