The Universe 25 Experiment

A mouse’s perfect paradise… or not.

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Between the late 1960s and early 1970s, American ethologist John B. Calhoun created a seemingly perfect utopia for mice. Calhoun’s predator-free, disease-free enclosure was furnished with limitless food and even an upper level with miniature mouse condos. Essentially, the mice would enjoy all the modern comforts people have come to expect today.

But the rodent society, dubbed the Universe 25, would quickly prove to be far from paradise.

The Experiment

To begin the experiment, Calhoun introduced four pairs of healthy mice into the enclosure. For the first 104 days, the mice explored their new habitat, marked their territory, and began nesting. Then, the population began to increase, doubling every 55 days.

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Interestingly, even when the population was well under 1/4 of the enclosure’s capacity, most of the mice still crowded together in select areas. Eating, for example, was a shared activity so mice would group together during feeding times even though there was plenty of space to eat by themselves.

By the 315th day, the population reached 620 mice. Crowding behavior discouraged mating, heavily contributing to dropping birthrates. Universe 25 would now begin its slow but steady decline.

A prominent social ladder quickly took shape. Within the male population, the most dominant mice were characterized by their extremely aggressive behavior. The so-called “alpha mice” would often engage in wildly violent bloodbaths, proceeding to attack, rape, and even practice cannibalism at the expense of their peers. Disturbingly, these violent outbursts usually had no clear provocation or motive.

On the opposite side of the spectrum were the least socially adept mice who were completely excluded from mating. They spent their time moving between larger groups of mice, eating and sleeping by themselves. Occasionally, these mice would also fight one another.

Any mice that fell between these groups were rather timid and often became the victims of the violence perpetrated by their more hostile counterparts.

As the social roles broke down, the females took on more aggressive attitudes of their own. Taking care of their nests in the midst of such a chaotic domain was no easy task, so many mothers would sometimes act violently towards their own litters. Others would completely withdraw from their motherly responsibilities, ignoring their litters and quitting mating practices entirely.

Day 560 marked the beginning of the end, sometimes referred to as the “death phase.” The spike in mortality rate fluctuated at around 100%, halting population increase altogether. However, the new generations that did survive had grown up in the tumultuous environment that was the Universe 25. These mice had no perception of the “normal” lives that mice led beyond the enclosure’s walls.

As explained in Thomas J. Elpel’s Roadmap to Reality:

Studies … have consistently revealed that an absence of social stimulus and maternal care leads to a high rate of physical and emotional retardation and mortality.

In the context of the Universe 25, isolation paved the way for a new category of mice that Calhoun called the “beautiful ones.” These mice were segregated from the other, bloodthirsty mice and the violence that plagued the rest of the enclosure. Their subsequently unruffled appearances were the inspiration for their name. Furthermore, being separated from the rest of the Universe 25 mice, the beautiful ones made no contributions to the society. The mice gave no help in mating, mothering, marking territory, etc. Instead, they spent all their time feeding, drinking, grooming, and sleeping.

Eventually, the beautiful ones outnumbered the more aggressive mice. Still, rather than mating or creating new roles in the Universe 25 society, the beautiful ones continued to exist solely for their physiological satisfaction. With everything provided for them in the enclosure, the paradox of the beautiful ones reveals the self-destructive patterns that emerge when living a life without purpose.

Soon, because of the collective indifference towards mating or building a sustainable society, the mouse population began to die out until there were no mice left at all.

Implications for Humanity

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The Universe 25 experiment offers insight into the demise of humankind. The beautiful ones in particular show us that individuals will not assume a productive role in society if they do not have proper relationships or role models in the environment they grow up in. Additionally, if there exists no conflict, no danger, or no “work” to be done in a society, its inhabitants, like the beautiful ones, will ultimately lose their purpose in life.

Yet, the Universe 25 is not a perfect parallel to humanity. As a more sophisticated species, we have access to science, technology, and medicine which can help us prevent such a dystopia. Having more outlets for creativity and analysis also allow people to find meaning in life beyond just eating or sleeping.

Most importantly, Universe 25 was a manufactured environment. At our current technological standards, we do not have a viable way to replicate Universe 25’s conditions. This includes ensuring the end of disease, hunger, and even natural disasters.

In the future, as technology advances, the conditions of the Universe 25 may become more achievable. Then, we will truly see how different the minds are of mice and men.

Fessenden, Marissa. “How 1960s Mouse Utopias Led to Grim Predictions for Future of Humanity.” Smithsonian Mag, Smithsonian Institution, 26 Feb. 2015,

Giaimo, Cara. “The Doomed Mouse Utopia That Inspired the ‘Rats of NIMH’.” Atlas Obscura, Atlas Obscura, 14 Sept. 2016,

Inglis-Arkell, Esther. “How Mice Turned Their Private Paradise Into A Terrifying Dystopia.” Gizmodo, io9, 24 Feb. 2015,

“What Humans Can Learn From Calhoun’s Rodent Utopia.” VictorPest, VictorPest,

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