In 1968, animal behaviorist John Calhoun built a "utopia" for mice, called Universe 25, to study the effects of overpopulation. The enclosure was designed to provide for the mice's every need, with unlimited food, water, and space. Initially, the population thrived, but after about a year, the mice began to exhibit abnormal behaviors, such as aggression, withdrawal, and a complete breakdown of social structures. Despite the abundance of resources, the mice stopped breeding, and the population eventually died out. Calhoun's experiment was seen as a warning about the dangers of overpopulation and social collapse, but some have interpreted the results as less applicable to human societies. However, Calhoun's later work showed that by introducing variables such as creativity and purpose, the mice could be encouraged to thrive even in dense populations.
Here are the key facts extracted from the text:
1. In 1968, John Calhoun built a utopia for mice called Universe 25.
2. Universe 25 was designed to satisfy the needs of its mouse inhabitants.
3. The enclosure was a tank 101 inches square with walls 54 inches high.
4. The tank had 16 vertical mesh tunnels and four nesting boxes.
5. The tank was designed to hold 3840 mice.
6. Calhoun chose four breeding pairs of mice for the experiment.
7. The mice were specifically bred for the experiment and were hands-picked from the National Institute of Health's breeding colony.
8. The experiment started with eight mice.
9. The population of mice grew to 620 within a year.
10. After day 35 of the experiment, the population growth slowed down.
11. After day 315 of the experiment, the social bonds among the mice broke down.
12. The mice began to exhibit abnormal behaviors such as attacking each other, abandoning young, and refusing to breed.
13. A group of mice withdrew themselves from the rest of the population and lived in the upper levels of the enclosure.
14. These mice lost interest in social bonds and refused to interact or mate.
15. The last birth in Universe 25 took place on day 600.
16. The population eventually dwindled and all the mice were dead a few months later.
17. Calhoun believed that overpopulation would inevitably lead to social collapse and extinction.
18. Calhoun continued to research and tweak environments to find ways to keep the mice from going extinct.
19. He had some success in encouraging creativity in certain mice, which helped them thrive.
20. Calhoun's work was sponsored by the National Institute of Mental Health.