In Calhoun's experiment, mice were placed in mouse utopia. Mouse utopia had plentiful food, water and free space. There were no predators.

You'd expect the mice population to grow until it runs out of space, right? Wrong. What actually happened was that the mice went insane from lack of challenges. The population peaked before all available space was taken and after a few generations the mice had become so dysfunctional that the colony went extinct.

Around the time the population peaked, the females became more aggressive towards males and towards their own young. They also became less nurturing. Males withdrew from society, some became homosexual and some went MGTOW. Each new generation of mice was more dysfunctional than the last, because the parents increasingly stopped raising their kids properly. Rat society broke down.

So what caused this? Again, the mice went insane due to a lack of challenges in everyday life.

I'm not the first to make this connection, but Calhoun's experiment may explain the dysfunction in our society. The west has for a long time been (and to a lesser extent still is) a place where there's abundant food, abundant water and almost no animals that try to eat us. And indeed, humans are behaving strikingly similar to how Calhoun's mice are behaving.