Inside Universe 25

“I shall largely speak of mice,” the paper begins “but my thoughts are on man.” So begins a truly extraordinary scientific paper, and an equally extraordinary story. “Death Squared: The Explosive Growth and Demise of a Mouse Population.” was published in 1973 by John Calhoun, and it detailed his increasingly bizarre research into the psychological effects of overcrowding. Over two decades he built a series of ‘rodent utopias’, where he could keep a population of rats or mice, meet all their basic food and shelter needs, but mess around with population levels. He wanted to see how they responded to having to live, cheek-by-tiny-jowl, with far more other rats than they were used to. And it wasn’t pretty. Social orders melted into chaos, rodents fought indiscriminately, or shut themselves away at the top of the enclosure. Mating orders collapsed, population numbers tanked, and eventually, every single rat was dead. His work came at a prescient time. In the 60s and 70s, the exponentially expanding human population was a hot-button topic, and ‘population panic’ was in full swing. Alongside the expansion of cities, creeping urban sprawl, rising city-centre crime rates and 'urban sinks', there grew a concern that human living conditions were about to take an interminable dive. How would we live, with so many of us on earth? Calhoun’s work was leapt on by the press and public as a dire prediction of our own coming collapse. His rodent utopias became a subject of great interest among architects and city planners, psychologists and sociologists, and anyone fascinated by the human condition. But has his work been misunderstood? 50 years on, what lessons can we take from the work of a ground-breaking but often misunderstood scientist, in the face of a human population now exceeding 8 billion. Emily Knight explores his extraordinary work, its implications for humanity, and the possibility of a human utopia, that might not look anything like you expect. Presented and Produced by Emily Knight in Cardiff

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Inside Universe 25 is an episode from Discovery by BBC.

This episode is 26:30 long.

This episode was published on Apr 20, 2026.

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