There’s an unfortunate corollary in science journalism; the flashier the headline, the more likely it is that the study being reported on was performed in a test tube or on a mouse. At this point, when I see headlines like ‘coffee: maybe killing you or maybe just helping you poop’ I go right on drinking another espresso to prepare my own human data.
But when one of those animal studies predicts an inevitable extinction as a result of overpopulation? I’m a little concerned about how we’re gonna sort out any human data.
Today’s Moment of Science… Universe 25 & Behavioral Sink.
Mice and rat studies are indispensable to the life sciences. The list of reasons is long and includes their small size, short lifecycle, and surprising degree of genetic similarities to humans. Yeah, there are more genetically similar critters used in research, but when testing out something brand new? Nobody’s getting funding for a lab full of macaque monkeys on day one of “I had a thought.”
It’s hard to pin down an exact percentage of studies in mice and rats that pans out in humans. Typically, about one in ten drugs that passes through trials on mice will make its way onto pharmacy shelves. But how often do psychology or sociology experiments in animals apply to humans? No, really, I’m asking, it’s the rare time when the internet doesn’t want to cough up an answer for me. Rude.
So, let’s see how well studies of mouse population dynamics in a closed environment can apply to the end of the human race. Light stuff today.
After John Calhoun completed his PhD thesis on the Norway rat in the early 1940s, his first large scale experiment was in 1947. These spoiled little fuckers had a 10,000 square foot outdoor pen. During the 28 month study, the population never rose above 200. The rats organized themselves, breaking up territory amongst a dozen or so colonies. The rodents found a happy equilibrium.
He continued studying and configuring rat pens through the 1950s. Then, in the 1960s, his famous research at the National Institute of Mental Health (NIMH) kicked off. Calhoun was trying to build his rodent utopia. He was sure eventually one of these pens could be set up with the right combination of Earthly delights to make a kumbaya existence for thousands of mice.
The new pen was called the “Mortality-Inhibiting Environment for Mice.” But after his first 24 attempted- and to various degrees, failed- mouse houses, you might know it as Universe 25.
A 9×9 foot enclosure standing 4.5 feet tall, this mouse paradise came with unlimited bedding, food, water, and 256 nesting boxes capable of accommodating over 3,800 mice.
So uh… would it surprise you to hear that nowhere near 3800 mice ever lived in Mouse Utopia?
They started with four breeding pairs. The critters took to breeding with some goddamn vigor. These itsy fuckers were doubling the population of New Mouse City every 55 days. At first.
By day 315, there were 620 inhabitants and still space to house over 3,000 more mice. But a population that had been doubling every 55 days now slowed to doubling every 145 days.
Calhoun had noticed the rodents’ tendency to crowd together even with ample space available. To be clear, this didn’t mean a few of them would accidentally pig pile at the food bowl when gathering with buddies. I mean they were ignoring most of the available space, society was breaking down, the population was in freefall, and they were just beating the fucking life out of each other like the mouse purge was upon them.
The term for this turn of events is ‘behavioral sink.’ And it was the beginning of the end for his perfect tiny mouse world.
Dominant males thrived at first, producing progressively douchier offspring. Nursing mothers became aggressive in turn, often kicking young out of the nest prematurely. If they survived, they had some goddamn abandonment issues and didn’t know how to mouse. There were outcast males who started little fight clubs in their ample free time. Then there were the non-dominant males. They were occasional targets of cannibalistic attacks by dominant males.
Then there were the ‘beautiful ones,’ the mice that tried to chill the fuck out away from everyone else and groom themselves excessively. They had no interest in sex though. Just like everyone else, they had no healthy socialization, and were better at looking pretty than bumping uglies.
The infant mortality rate skyrocketed. The population peaked on day 560 with 2,200 mice. The last birth in Universe 25 was on day 600, at which point pregnancies virtually stopped. The population dwindled to its slow demise over the next three years.
So, uh, now that this end times scenario is seared into our nightmares, anyone else want to know where this falls on the list of potential ways that humanity bites it?
To be fair, we haven’t ruled it out. And the internet is filthy with speculation that this is how it ends. Calhoun also thought we could all turn into cannibalistic rage mice if shit got too cramped. In the publication of his research, he said there’s “no logical reason why a comparable sequence of events should not also lead to species extinction.”
This has been your Moment of Science, not too worried but also not telling you what my plans are for the purge.
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