In 1972, John B. Calhoun built an utopia for mice. Every aspect of Universe 25, as this particular model was called, was designed to cater for the well-being of its rodent residents, increase their lifespan, and allow them to mate. It was not the first time the ethologist had built a world for rodents. Colhoun had been creating Utopian environments for rats and mice since the 1940s, with consistent results: overpopulation leads to explosive violence and hyper-sexual activity, followed by asexuality, self-destruction, and extinction.
