Universe 25: The Rat Utopia Which Became a Rate Dystopia

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Podcast Transcript

Have you ever wondered what it would be like to create a utopia? A place where all your wants and needs were taken care of and there was never any fear of harm? 

Creating such a world for humans may be far off, but one man did try to create a utopia for rats. He created a world that had everything they would want and where all their needs are taken care of.

It didn’t turn out like anyone expected. 

Learn more about Universe 25, and how a utopia turned into a dystopia, on this episode of Everything Everywhere Daily. 


If you take a strict definition of the scientific method, you first create a hypothesis, and then you conduct an experiment to test the hypothesis. 

While it is great when science works this way, often the most interesting results come when someone just says “let’s try this out and see what will happen”.

This was the impetus behind the study which was the subject of this episode. 

An ethnologist by the name of John B. Calhoun who worked at the National Institute of Health devised a study in 1958 that would take place on Norwegian rats. In a barn in rural Maryland, he created what he figured would be a rat paradise.

In this rat utopia, there would be no shortage of food or water. There would be no predators. Plus, there would be plenty of space for the rats to live and build nests. 

The area for the rats was divided into four parts that were 3.0 m × 4.3 m × 2.7 m in height. There was a hallway around the structure, and all of the rooms had glass ceilings so the researchers could see what was happening. 

He ran these experiments for a total of four years before having to cease the experiments to take a sabbatical at Stanford. 

He wrote up his findings for Scientific American, and the results became famous in several communities. But more on the results in a bit.

In 1968, he once again went back to the rat utopia blackboard, and this time he ran the 25th version of his experiment, hence the name, Universe 25. 

This setup was a bit different. For starters, he used mice instead of rats, and he created some vertical tunnels for the mice to access nesting areas, but other than that, the mice would have everything they needed. 


The only real limit on the mice was space. There was a finite amount of space, but he estimated that Universe 25 could hold 3,840 mice.

The experiment started with eight mice, four males, and four females. They were put into Universe 25 and allowed to be the best mice they could be.

At first, everything went great. The mice spent a lot of time eating, running around, and reproducing. 

The time it took to double the population of mice was 55 days. 

The mice slowly began taking up all of the space that was available, and the mouse population kept doubling at the 55 day rate for several months. 

However, when the population hit about 620 on day 315, something happened.

The mouse society began to change. Starting with day 315 the time it took for the population to double rose to 145 days, up from 55. 

For about the next 330 days, the mouse society in Universe 25 began to break down and the behavior of the mice changed radically. 

Baby mice were often kicked out by the mother before they were finished weaning.  Young mice were often attacked. Dominant males would often start fights for no apparent reason and became extremely violent. They would often resort to cannibalism. 

Females became aggressive with other females. Non-dominant males basically just gave up and wouldn’t fight back when attacked. 

Eventually, the new mice were born into this system and didn’t know anything else. 

On day 560, population growth basically halted. The total mouse population hit 2,200 mice, which was well below the number of mice that the universe could theoretically hold. This began what became known as the death phase. 

On day 600, the last mouse was born.  Reproduction among the mice totally stopped. None of the mice, male or female, were interested in reproducing. 

One group of mice separated themselves and they were dubbed “the beautiful ones” by the researchers. They did nothing social. They didn’t reproduce. They didn’t mark territory. They didn’t fight. They didn’t do anything. They engaged in no social activity whatsoever. 

The mice at the point had no clue how normal mice behaved. They never grew up in that world. 

Eventually, the entire population of Universe 25 became extinct. It wasn’t from a lack of food or water or even space.  There was plenty of space, especially towards the end as the population was nearing zero. 

What Calhoun found in Universe 25 was basically the same thing that he found in all the other previous 24 universes. 

The population would grow rapidly. At a certain point, the mice or rats would engage in anti-social behavior and the social order would collapse. All the mice would shift to solitary activities, reproduction would plummet, and eventually, the population would go extinct. 

Calhoun dubbed this change a “behavioral sink”. 

The big question on everyone’s mind was, what did the results mean? 

One problem is that everyone seemed to read into the experiment whatever they wanted to. There have been many different interpretations of what the results meant. 

The first and most obviously direct interpretation was that the change in behavior was due to overcrowding and overpopulation. 

This is certainly a plausible hypothesis, however, the population didn’t come close to its maximum capacity, and given the parameters of the experiment, there was never a shortage of resources. 

Another explanation has to do with social roles. There are only so many social roles that can be filled in a mouse society. When mice fall outside of those roles, such as being a dominant male, in nature they would just go off somewhere else, perhaps find a different mate. 

In Universe 25, there was nowhere to go. This caused social problems to be inserted into the mouse society that otherwise would never exist in nature. 

Yet another theory was that there was too much socialization. Laboratory rats raised in isolation can often have stunted development, however, perhaps there can be problems at the other end as well. 

Those were just the theories to explain what happened to rats and mice. 

Everyone then had theories for what they meant for humanity. 

In the 1960s, some felt that the overpopulation and dense crowing in cities like New York led to a general sense of apathy. This, it was claimed, was reflected in the murder of Kitty Genovese in 1964 which was reportedly witnessed or heard by 38 people, none of whom came to her aid or called for help. 

The experiment was used to explain the breakdown of the family. Female mice unwilling to care for their young and violent males were compared to what was happening to people. 

Movies like Soylent Green were analogous to what some people thought happened in Calhoun’s rat universes. 

Recently, some people have been making connections between the experiment and how people react on social media. They compare the behavior of subgroups of people on the internet to how some of the mice behaved when they suffered from too much socialization. 

However, many of these opinions were just that. Opinions. They weren’t backed up by any actual data, they were just ideas that people were spitballing. 

For obvious reasons, it would be very difficult to replicate a study like this with humans. It would take decades to carry out, not even considering the ethical issues of keeping someone locked up for that much time. 

However, some limited studies on humans were done. There were some sociological tests done on people with limited, extreme crowding, but they didn’t get results anything like what Calhoun found for mice and rats. 

Eventually, researchers began to offer more technical critiques of Calhoun’s experiment. 

For starters, they noted that the utopia he build was really just a prison. The mice did have everything they wanted, except for space. That isn’t much different than humans in a prison who are fed.  Mice in the wild would never live their entire lives in confines so small. 

As with prison, it allowed for the most aggressive mice to control everything, which eventually led to the breakdown of the whole society. 

Over the years, the interpretation of Calhoun’s experiment has changed to reflect whatever the current issue of the day is. 

Ultimately, humans are not rats or mice, especially when it comes to socialization. Humans have long memories and can reason our way out of situations that rodents can’t.

Nonetheless, the rodent experiments of John B. Calhoun have been the inspiration for several fictional works including Judge Dredd, & Mrs. Frisby & The Rats of NIMH.

Calhoun’s ratopia experiment was odd in that, at least scientifically, it wasn’t really useful to explain much of anything. It was a fascinating study, but people are still arguing about its implications and why it went the way it did.


However, as a metaphor and a cultural touchstone, the experiment was a huge success. 


Everything Everywhere Daily is an Airwave Media Podcast. 

The executive producer is Darcy Adams.

The associate producers are Thor Thomsen and Peter Bennett.

Today’s review comes from listener nutjob over at Apple Podcasts in the United States. They write, 

Almost perfect

“Everything Everywhere Daily” is nothing short of brilliant. Gary Arndt’s bite-size recounting of history, science, geography, cuisine, etymology, and points in between are the perfect distraction for any time of the day. I personally like to let several of the “amuse-bouche” episodes pile up and then settle in for a long dose of engaging and engrossing information. Arndt tackles historical figures you know and don’t know, finance (like the fascinating history of credit cards), mathematics like the prime numbers and conditional probability, and even where and how our everyday eating utensils came to be. It’s perfect…almost!

The only thing I can’t stand is the “five star reviews” he reads at the end of each episode. Gary Arndt’s found a sneaky way of making sure his podcast is at the top of the charts: he essentially bribes people to have their own words spoken by him—but if they leave five-star reviews. That’s an underhanded trick, buddy. And it’s not nice.

The podcast—on content and delivery alone—is worth five stars, absolutely! But teasing people with the chance of fame (“Hey ma, listen, I’m on the air!”) to boost ratings—and making me fast-forward through those inane reviews—is why I can only give four stars.

Ok, Nutjob, I need to explain to you how the Apple Charts work because your understanding of it is wrong. 

Reviews have nothing to do with how Apple ranks podcasts on the Apple Charts. Nothing at all. All the five-star reviews in the world will not do anything to help a podcast. 

This isn’t just me saying this, this is directly from Apple itself. 

From the Apple Podcast website, 

Although ratings, reviews, and shares also help indicate a podcast’s newness, popularity, and quality, they are not factored into the algorithm that determines the rankings for Top Shows and Top Episodes. In other words, they may not help people find a podcast on their own, but they influence whether people will listen or follow, and those factors influence the charts.

I have placed a link in this episode’s show notes to the page on the Apple website where you can read this for yourself. 

So I’m not gaming or cheating anything. I am not at the top of the charts, which you are free to verify yourself. The top of almost every chart category is almost always podcast by large companies. I am a one person operation. 

This show is currently usually ranked about 50-60th in the Apple history charts in the United States. I have never been anywhere close to the top of any chart, except for some reason in the country of Malta. 

The only thing which determines where you rank on the Apple charts is the number of people who actually listen and subscribe to the show on Apple, with a bit of a bias towards new listeners. That’s it. 

So why do I read reviews every episode?

First, is that yeah, I certainly want people to leave good reviews for the show. I’m guilty of that. Podcasts primarily grow through word of mouth. While the algorithm isn’t affected by reviews, human beings certainly are. No different that using Yelp or TripAdvisor or Amazon, good reviews are a means of social proof to people who might be new to the show.  So I absolutely encourage people to leave a good review if they enjoy the show, and I’m not going to stop encouraging that. 

Secondly, podcasts do not have a like or share button, and there are no comments. Reviews are one of the only ways people have to actually interact with a podcaster. That is why I don’t just read reviews from Apple, although they are the majority of them because they are the most popular podcast app.

I’ve read reviews from PodcastAddict, PodcastRepublic, Castbox, Podchaser, Instagram, Patreon, Twitter, and even emails sent to me directly.

Any sort of feedback and interaction is great for me because otherwise there would be nothing. So if you want to leave a review and hear me read it at the end of the show, sure. I’m happy to do so. 

Just like I did it for your review. 

Remember, if you leave a review or send me a boostagram, you too can have it read the show.