In 1968, researcher John B. Calhoun conducted a famous experiment known as “Universe 25,” in which he created a "mouse utopia" with unlimited food, water, and no predators. At first, the mouse population grew rapidly, but as overcrowding increased, their social behaviors began to deteriorate.
Mice formed aggressive cliques, mothers neglected or attacked their offspring, and some individuals became isolated and apathetic.
Despite the continued abundance of resources, reproduction eventually ceased altogether, and the population collapsed to extinction.
Calhoun described this phenomenon as a "behavioral sink," suggesting that social breakdown, rather than material scarcity, was responsible for the collapse.
