The Universe 25 Mouse Experiment

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 hypersexual activity, followed by asexuality, self-destruction, and extinction.