The “Universe 25” experiment is one of the most chilling scientific studies ever conducted, aiming to explore aspects of human societies through the behavior of a colony rats. The results and the implications were terrifying.

In the 1960s, ethologist John B. Calhoun crafted an experiment: Universe 25. A maverick scientist obsessed with how environments shape behavior, Calhoun built a mouse paradise, a 9-foot-square enclosure with endless food, water, and nesting spots, free from predators or disease. Starting with four breeding pairs, he watched to see what happens when life’s too easy and space gets tight

Initially, the rat population flourished, experiencing rapid growth. However, as their numbers increased, social issues began to emerge. The rats became more aggressive, territorial, and antisocial.

Female rats displayed heightened aggression, withdrawal from social interactions, and a reduced interest in reproduction. This led to a decline in birth rates and an increase in mortality among younger rodents.

A new group of male rats, known as the “beautiful ones,” emerged during the experiment. These rats showed little interest in mating or defending territory; their primary concerns were food and rest.

Eventually, the “beautiful males” and socially isolated females became the predominant groups within the population.

As time passed, juvenile mortality rates reached 100%, and reproduction ceased entirely. Homosexual behavior was observed among the remaining rats, along with an increase in cannibalism, despite an abundance of available food.

John Calhoun replicated this experiment 25 more times, with consistent results each time.