Mouse UtopiaIn 1968 Dr. Calhoun created 'Mouse Utopia' a large fixed environment with unlimited food, and water, free of disease and predators intermittently cleaned and regularly resupplied. Four pairs of mice were introduced into the 'utopia' on July 9 1968. Initially they thrived exhibiting exponential growth then something changed.
http://tomax7.com/HeyGod/misc/MousePopulationStudy.PDFAs the unusually large number of young gained adulthood they had to remain,and they did contest for roles in the filed social system. Males who failed withdrew physically and psychologically; they became very inactive and aggregated in large pools near the centre of the floor of the universe. From this point on they no longer initiated interaction with their established associates,nor did their behavior elicit attack by the most territorial males. Even so, they became characterized by many wounds and much scar tissue as a result of attacks by other withdrawn males.
As a result of the extreme demands made on territorial males their ability to continue territorial defence declined. Gradually the frequency of this involvement in territorial defence declined as did the area defended. This left nursing females more exposed to invasion of their nest sites. Normally nursing females in the presence of territorial males exhibit little aggression. However, in response to invasion of nest sites and bases of ramps leading to them, the nursing females did become aggressive, essentially taking over the role of the territorial males. This aggression generalized to their own young who were attacked, wounded, and forced to leave home several days before normal weaning.
Maternal behavior became disrupted. Young were often wounded in the delivery process. Females transported their young to several sites, during which process some were abandoned. Many liters of young age on one survey disappeared before the next survey.
Population increase abruptly ceased on Day 560 after colonization. A few mice born up until Day 600 survived past weaning. Between these times deaths just slightly exceeded births. Beyond Day 600 the incidence of pregnancies declined very rapidly. Last conception was about Day 920.
Male counterparts to these non-reproducing females we soon dubbed the 'beautiful ones'. They never engaged in sexual approaches toward females, and they never engaged in fighting, and so they had no wound or scar tissue. Their behavioral repertoire became largely confined to eating, drinking, sleeping and grooming, none of which carried any social implications beyond that represented by contiguity of bodies.
Most of the last of the population born were fully or largely like these non-reproducing females and these 'beautiful ones'(males). At this time only the 'beautiful one' category of males, and their counter part females, remained at an age normally compatible with reproduction, but they had long since failed to develop this capacity.
By March 1 1972, the average age of survivors was 776 days, over 200 days beyond menopause. On June 22 1972, there were only 122 (22male,100female) survivors. Projection of the prior few months of exponential decline in numbers indicates that the last surviving male will be dead on May 23 1973,1780 days after colonization.The population will be, reproductively,definitely dead at that time, although such death was predicted by 700 days after colonization. This demise of a population contradicts prior knowledge which indicates that when a population declines a few remnant groups, some individuals will reinitiate its growth.
The results obtained in this study should be obtained when customary causes of mortality become markedly reduced in any species of mammal whose members form social groups.
Prior theory indicated that a population in this type of environment would stabilize not go extinct. So why did it the mice in 'mouse utopia' die off? Some have argued that increasing mutation load is the cause but I find such arguments unpersuasive. Dr. Calhoun created an environment that destroyed the social structure and social behaviors of mice. This led to their extinction.
Biology is often conserved and there is a simple biological model that expanded and extrapolated might account for the extinction seen in mouse utopia. That model is one of
cellular apoptosis.
This experiment provides a contextual framework for the observations and papers upthread showing that both active group involvement in religious organizations and active group involvement in secular organizations are associated with health benefits.
