Throughline - Of Rats and Men (2022)

Episode Date: February 23, 2023

Rats. Love 'em or hate 'em, (though you probably hate 'em), they're part of our world. And they've been out in full force: In New York City, health data show rat sightings doubled in the past year. It turns out they're a lot like us: They've colonized the whole planet; they're incredibly adaptable; they go wherever the resources are. And, they share one-fourth of our genome—meaning that when you look in the mirror, you're kinda seeing a rat staring back at you. So for this episode, we dove into the history of our rodent doppelgängers. What we found was a story that spans thousands of years and nearly every continent on Earth, from the fields of ancient Mongolia to the palaces of Victorian England to the laboratories of 20th century Maryland... and probably to a burrow near you.Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy

Support for this podcast and the following message come from the NPR Wine Club, which has generated over $1.75 million to support NPR programming. Whether buying a few bottles or joining the club, you can learn more at nprwineclub.org slash podcast. Must be 21 or older to purchase. Hey everyone, Run here. I am not a fan of rots, to put it lightly. And yet they seem to be everywhere I go lately. And it turns out, it's not just me. I just saw a news report showing that rat sightings in New York City doubled over the last year. I had to know what was going on. Alright, okay, so you ready for this? Yes.

Alright, so we're walking. It's a nice day today, very sunny. Surprisingly, no rats yet today. No rats yet. In sight. Because there's street sweeping, apparently. Yeah, but I'm sure that's going to change once we meet up with Bobby. Bobby Corrigan.

Yeah, rodontologist. Rodontologist. Rodontologist. Yeah, yeah, All things rodents. It took a while, but eventually I convinced ThruLine producer Lawrence Wu to go with me on a New York City rat safari. See the left, look to the right. Any rats? No? Well, just wait, just wait.

I think about rats a lot, like an unhealthy amount. Yeah, Run talks about rats all the time. Yeah, yeah, I'm sort of the rat lady of ThruLine at this point. But how could I not think about them? I live in New York City, in Manhattan, right next to this small empty plot of land where a brownstone once stood. That's now basically a rat condominium. They hang out on the sidewalk. They jump out from behind my trash can.

They run up and down the curb. They're often the first thing I see when I leave my apartment and the last thing I see before I walk into it. At night, 100% hands down, you walk, it's like a party. Whether or not you live in New York City, you've probably encountered a story or two about rats, especially during the early days of the pandemic. Warning this morning from the CDC, watch out for hungry and aggressive rats.

We have been seeing reports from around the country that rats were on the move, and you might start seeing them in areas where they had not been a problem before. Homes, garages, and even cars. Boston City Councilor said they're getting increased rat reports from nearly every neighborhood. It's absolutely disgusting. Large rats climbing all over a Bourbon Street pizza counter. Rats. That's what they're saying in San Francisco after rodents moved into a playground and parents want those rats gone. Aristotle once theorized that nature abhors a vacuum. During the pandemic, as humans retreated into their homes, the natural world reclaimed some space.

And rats, well, they're especially good at filling a vacuum. That's arriving. And what's more, these rats seem to have gotten an attitude. Trust me, even if you don't think you care about rats, we are going down the subway station. By the end of this story, I guarantee you will. I'm Randa Abdel-Fattah, and on this episode

of ThruLine from NPR, we're investigating the hidden life of rats. Our rat safari was set to begin at Collect Pond Park, a small one-square-block park in New York City's Chinatown that was once the site of a pond, and later a jail. But nowadays, it's home to a whole lot of rats. So it makes sense that's where Bobby Corrigan, rodentologist and rat safari guide, asked us to meet him. Hey, Bobby. How we doing? Good. Bobby grew up loving nature. He'd spend

hours watching and studying the bugs in his backyard. He says he always knew he was destined for some kind of environmental work, but that he stumbled across rats by accident in his backyard. He says he always knew he was destined for some kind of environmental work, but that he stumbled across rats by accident in a barn. The rats in his barn, I just sat there for a couple hours one day and I'm watching him do all these things. I said, you know, I got to know more about this animal. And the more I studied them,

the more I realized, you know, this is awesome. And this is an awesome animal. Rats became a lifelong passion and profession for Bobby. These days, he's a scientist who helps companies and local governments rein in their rat problems, retracing rat footsteps, figuring out the hot spots, coming up with solutions. Although, he admits, it doesn't make him the most popular dinner guest. You know, you're holding a classic wine glass in your hand. Well, what do you do for

a living, right? I used to say, well, I study rats in cities. And you could just see people, like, they do this. Like you have rats in your pocket or something. Yeah, and they'll say to their spouse, hey, you know what, we need to refill our wine. It was great talking with you. I'm sure some of you are thinking, yeah, I definitely try to get out of that conversation. Why would I want to hear about rats at a party? They're gross. They're creepy. They sneak around at night with those long tails and daggers for teeth. And from where I sit, anybody who thinks otherwise has only ever encountered a rat in Ratatouille or the Rats of NIMH.

And there's been really good studies recently out of Vancouver University of British Columbia showing the mental stress rats cause on us. It's very significant. Some people just can't sleep at night. You know, they stress out if they see a rat. They can't concentrate during work. It's a big deal. It's a big deal.

Yeah, you might be in there. I think I went through that. But honestly, because I was seeing so many rats, I think I was feeling that anxiety, that stress of being like, I can't escape them. They're everywhere. Everywhere I look, I see plastic bags, and I'm like, it's a rat. But it's a plastic bag.

Okay, not my proudest moment. And I'll admit, I started out the safari thinking this was a uniquely New York thing. We're home of the pizza rat, after all. For those of you who don't know, this video of a rat pulling a giant slice of pizza twice its size, step by step, down the stairs of a subway station, got 12 million views on YouTube. It's funny, I was, two years ago I was in Norway, and there was a person on the rail, and they had a pizza rat button. And it was pizza rat, and it didn't say New York City, it just said pizza rat. I said, I'm from New York. He said, oh, pizza rat. It was like, I was famous for pizza rat. So I was like, oh my god, you know.

But Bobby quickly followed up by pointing out that in his travels all over the country and around the world studying rats, he's found this problem exists in pretty much every major city. Rats have taken over the world. They've occupied almost the entire planet. You know, the only one more successful than it in that group is the house mouse. So we're number one most successful species. So we say number two is the house mouse. And after that, the rats probably come in at third. So how can you not like an animal that is smart and adaptable and resilient? Let that sink in for a second.

Humans, mice, and rats are among the most successful mammalian colonizers of the earth. And that's not all we share in common. They tend to be homebodies. They love baked goods. Baked goods? Baked goods. The more Bobby described how rats live...

They're loving, they learn words, their commands, and so forth. The more I was struck by how weirdly similar they are to me, to us humans. This animal is able to, as it's moving about, it's visually recognizing things like we do. Like, remember to make a left at the light where the Starbucks is. Well, they have different visual cues, right? So all along the way, they're looking for vision. I have to admit, my respect for rats was starting to grow. And my curiosity about how they ended up in New York City, and it turns out pretty much every other major city, was also growing. So Lawrence and I got together with the rest of the ThruLine team and began digging into their history. What we found was a story that spans thousands of years and nearly every continent on Earth,

taking us from the fields of ancient Mongolia to the palaces of Victorian England to the laboratories of 20th century Maryland. Our Rat Safari continues when we come back. Hi, this is Taylor from Dolphacopter, and always get the real-time mid-market exchange rate with no hidden fees. Download the WISE app today or visit wise.com. T's and C's apply. Part 1. Eating from the same table. You know, you kind of see the landscape, and you're looking for signs of rats everywhere. Are there burros there? Is there rat feeding in that corner? So yeah, they're just, to me, like part of the city. This is Dr. Jason Munshi-South. He's a professor of biology at Fordham University in the Bronx, where he leads his own research lab. And since about 2008, when I moved to New York City, I've been studying the effects of urbanization on wild animals and also pest species like rats. Jason's lab focuses on understanding how humans

and cities affect wild animal populations in those places. So I called him up to get a little more insight into what is up with New York City's rats. And when we were getting on our Zoom call for this interview, something caught my eye. Well, first of all, I got to ask, I love your background. Where did you take that photo? Yeah, that's actually, it's a Shinto shrine in Kyoto, Japan that's dedicated to rodents. Oh my gosh. It's a tiny little place I found by accident. To his left and right, two statues of rats sit atop small stone pyramids, pedestals really. One rat is tall and slender, the other short and stout. And each of

the rats is holding onto something. One is carrying a scroll and one is carrying a jar of sake. And so the scroll is to symbolize wisdom and the jar of sake is like abundance. And so right from the start, it was pretty clear to me that Jason Munchie's self would know a thing or two about his rat neighbors. They're primarily nocturnal. They live in burrows, so they'll burrow into soil and spend, you know, most of the day down there. And they build these colonies, almost like villages of related rats. They're highly social. They spend a lot of time with other rats. They have to be somewhere near water sources. And they are, you know, territorial to some degree. So males will fight with one another.

You'll find, especially males with lots of wounds and things as they get older from battles with neighboring rats. Over time, they'll add more tunnels and they'll start to connect. They'll sort of overlap with neighboring boroughs. And so it becomes this big tangle. Like a subway, but for rats. So I've seen them, you know, in like New York City parks where there wasn't a lot of control going on. Where you could count like 300 holes and you could just watch them coming in and out all day.

That makes me never want to sit on a patch of grass again in the city. But for Jason, seeing all those rats coming in and out of those rat holes sparked a question. What's going on with rats in New York City? How did these animals get here? This was long before the pandemic, long before RUN was grappling with that question. And Jason decided to build a whole study around it. The first thing he discovered was that New York City is actually overrun by just one kind of rat, the brown rat. Their Latin name is Radus norvegicus, which would translate to the Norway

rat, but that's a misnomer. They did not originate in Norway. We don't exactly know why they have that name. The most likely story is that the British naturalist John Birkenhout mistakenly wrote that the rat had arrived in England from Norway. And the mistake stuck. Jason and his team decided that in order to find the actual origin of the New York City rat, they had to compare its DNA to other rats in the world to find a match. Kind of like an Ancestry.com or 23andMe, but for brown rats. So he and his team started calling and asking labs around the world to send them DNA samples of their brown rats. We ended up with, you know, like 500 samples all around the world. And we just decided, OK, let's do this properly and try to understand what major groups of rats exist everywhere and use that as context to understand what rats are in New York City.

And what they found was that all the signs were pointing to a place thousands of miles east of Norway. As far as we know, they originated in East Asia. Likely in a region between northern China and Mongolia, a couple million years ago. It's likely that originally they were living along like streams, sort of grassy savanna areas where there was water sources. They're probably eating all sorts of things, seeds, fruits, insects, you know, snails. They've even been found in coastal areas to eat like mussels and things. And for a long time, the brown rat kind of did its own thing.

So the question is, how and when did our paths get so intertwined? When did they become commensal with humans? Commensal is this Latin term that basically means eating from the same table. And they probably began utilizing human foods when agriculture began in China. And that was, you know, 11,000 years ago. And initially, you know, the records suggest that farmers were growing things like millet and then switched to wheat. And so it's probably that period when humans began growing grain in large amounts and storing it for their purposes that rats started feeding on it. And, you know, some of them may have become

pretty specialized to do that. They just live around humans and eat our food. And from those early days in Mongolia, they started freeloading more than just food. They moved in with humans. They think this is pretty cool. It's warm because they don't hibernate. They can't hibernate. So they're thinking, so I don't have to worry about all this energy to stay warm. So there's a fire in here. It's warm.

These people drop food. They spill food. They're messy. And whatever this species is, which is us Homo sapiens, they think life is pretty good. But how did the brown rat go from Mongolian fields to shacking up with humans to riding the subway train downtown with me? It seems like brown rats kind of stayed for a while and they didn't really spread out for a long time, for hundreds of years, maybe thousands of years. And then boom, something happens.

Our dates suggest less than a thousand years ago, they got to Southeast Asia. By the time they got there, you know, humans had more advanced ships and you were starting to to see regional trade through the Indian Ocean and even up into Europe. Cities start building up, human populations are expanding, and you see the brown rat just getting everywhere. But the great brown rat migration didn't end there. In fact, in order for the brown rat to take over the world, they needed to hitch a ride with humans looking to take over the world. Rats would hang around ports, waiting to board ships that were stocked with all kinds of foods, perfect for rats to feast on. And it turned out, in the 17th and 18th centuries,

there were a lot of ships moving around the globe. It was the age of conquest. The British Empire, the Dutch, the Spanish, the French, they were all moving rats all over the place. In North and South America, in Africa, in New Zealand, in Australia. Whenever a ship docked in a new place and brown rats encountered a rival rat species there, they would ruthlessly fight them off, staking their claim to that new place. And their biggest competitor, the second most common rat in the world, was the black rat. Aka the black rat, a.k.a. the roof rat.

They're smaller, less aggressive, more prone to fight than fight. No match for the brown rat. And at some point, one of those ships crossed the Atlantic and made its way to us. So our rats likely came from the ports of England. And there's evidence that, you know, the brown rat was in New York City by the time of the American Revolution, almost certainly from, you know, British imperial ships. And it wasn't just New York City ports getting all the brown rat love.

Basically every port city. Boston, Philly, Sydney, Mumbai. And then once they were in all those ports, they just moved inland across continents. And so they hitched a ride with humans. And, you know, we can look at their history as kind of a proxy for human history because humans moved them around, around the world. Rats have been our companions for a long, long time. And you know what they say about couples.

The longer you're together, the more you start to resemble one another. They're very intelligent. They're very adaptable. Just like humans, you know, they moved around with us because they can live in lots of different places and figure out how to survive. They also, you know, they're not lone wolves.

They're like humans. They're very social. And part of their survival is going to be because they live in these groups. They've even found that they laugh. I think there's a lot to like about rats. But of course, there's also a lot not to like about them. So the viruses and rodents go hand in hand.

So do the bacteria, so do the fungi and protozoans. So it's an animal we don't want in our cities for that reason. And what better example of that than the plague? Black rats were believed to have helped spread a bacteria that killed millions of people across Europe in the 1300s. More current theories point towards the plague being spread by lice and fleas on human beings. But rats had a bad reputation as they ran wild in European cities, especially in London where writers like Shakespeare and Charles

Dickens couldn't help but add them into their stories. Our natures do pursue, like rats that raven down their proper bane. A thirsty even, and when we drink, we die. When it came to rats, Victorian London was kind of what New York City is today. A rat city. Nobody near me here but rats, and they'll find stealthy secret fellows. To this day,

some believe London has more rats than humans, though it's hard to say if that's just legend talking. And then, like now, the frontline defense we have against rats are people whose job is to meet them in battle. So we put the flashlight on the floor and we looked. There were rats running everywhere. Coming up, we meet one of history's most famous exterminators. A rat catcher fit for a queen. This is Anya calling from Washington, D.C., and you're listening to ThruLine. Support for this podcast and the following message come from Autograph Collection Hotels,

offering over 300 independent hotels around the world, each exactly like nothing else. Hand-selected for their inherent craft, each hotel tells its own unique story through distinctive design and immersive experiences, from medieval falconry to volcanic wine tasting. Autograph Collection is part of the Marriott Bonvoy portfolio of over 30 hotel brands around the world. Find the unforgettable at Aut autographcollection.com. If you're listening as a subscriber to ThruLine+, we just want to say thank you. And if you're not yet a subscriber and want to learn more about how to listen to the show without any sponsor breaks, head over to plus.npr.org slash ThruLine. Becoming a Plus subscriber helps support all of our work at ThruLine. So we hope you'll join. Now, back to the show.

Part two, the fancy rat. Hello. Hi, is this Benny? This is Benny. Hi, Benny. My name is Run. This is Benito Camacho. You can call me Ben. Ben was born and raised in Harlem, not far from where I live now. He works for a company called VJ Pest Management. You're always nervous, no matter what. I don't care what exterminator would say, I'm not scared.

No, your heart is always pumping when you're dealing with a rat because it just takes one bite. So I'll tell you a rat story. I'm going to tell you a rat story. I'm ready. I'm ready. And this is Ron of City Express Pest Control. He's been an exterminator for over 30 years. In fact, he and his brother and two sons are all in the morning. So he went, he got the keys, I put him in the lobby and I locked the door behind him and I left. So in about 15 minutes, I get this call from him,

frantic, screaming, like he was being murdered. I was like, what's the matter? What's going on? He goes, you gotta come get me right now. I said, all right.

So I did turn around and I went back to him. I opened up the door. And I said, what's going on? I said, go in there. Go ahead. Go in there. Go in there and look.

So I went in there with him. And it was very dark. So I put my flashlight on. There were rats running everywhere. I mean, I'd never seen so many rats in a restaurant in my life. They were just running. They were everywhere. You couldn't have got me down that hole if you threw me down there.

There was no way at nighttime I was going down there exterminator enough. Too many rats for a rat catcher. I mean, what chance do I have against them? If you ever caught one and you have to fight one, just remember it only takes one good kick to their head because they have sensitive ears. All right. Okay. Have you ever kicked a rat in the head? All the time. Oh, really? Okay. So it works. All the time. All the time. After talking to a few New York City exterminators, we began wondering how other cities handled their rats. So we got in touch with Andy Brigham.

I'm Dr. Andy Brigham. I'm Rent2Kill's head of science. Rent2Kill. You pay, they exterminate. They've been in business for nearly a century now, and they've got the global exterminator market on lock. I think we're in something like 92 of the world's 100 largest cities now. Andy was talking to us from Rent-A-Kill's headquarters about an hour south of London,

where Rent-A-Kill developed a lot of its early rat-catching techniques. London is a place that, like New York, has an identity tied up with the brown rat. I've had them referred to as our brothers of darkness or something. I mean, you know, rats. And Andy says it was back in the Victorian era that the rat-catching business really took off, and rats began occupying a different place in our society. So we sent our former intern-turned-ace producer,

Anya Seinberg, down a rabbit, or should I say rat hole, trying to track down what was going on in London at that time. The London rat is an animal of legend. It's described in famous novels and in widely read poetry. In Victorian England, rats were everywhere in the culture. They were a constant threat, lurking in the shadows. But they were also carried around by rich people in cages, like some kind of trophy, and forced to fight to the death in the city's underground gambling rings. It was a strange existence, one of constant terror and terrorizing, caged comfort and intense fear. And as you can imagine, there were also some very weird human beings

involved in the creation of this reality for rats. Perhaps the most notorious, or famous, depending on who you ask, was a man with a very catchy name. Jack Black. He enjoys the reputation of being the most fearless handler of rats of any man living. Playing with them, as one man expressed it to me, as if they were so many blind kittens. Black was rugged, a florid complexion, bushy black hair, bushy eyebrows.

This is amateur rat historian Gerard O'Sullivan. I'm currently a higher education consultant, but my original training was in 18th and 19th century British and continental literature and culture. I grew up in New York City, and I rode the subways quite frequently. And anyone who knows New York knows that just as humans love the subway system, so do rats. So I've been fascinated by rats since, I would say, young adulthood. When he was in grad school studying British literature, Gerard stumbled across a book by a journalist named Henry Mayhew called London Labour and the London Poor. I saw his hand dip into the cage of rats and take out as many as he could hold, a feat which generally caused an oh of wonder to escape from the crowd,

especially when they observed that his hands were unbitten. That book influenced Charles Dickens and dozens of other writers and authors. It was really the first work of qualitative sociology, at least in the English language. And also my first encounter with Jack Black. Jack Black lived during a time of change. The Industrial Revolution had transformed England. New factories were popping up, and millions of people were crowding into the city to work at them,

hoping for a better life. It was a city of extremes. Nightmarish poverty existed shockingly close to outlandish wealth. Starving children begging at the feet of finely dressed aristocrats. High society snobbery built on the backs of exploited workers. And when those workers arrived in London, there was an animal there, waiting for them. Radus norvegicus. The Norwegian brown rat.

The brown rat arrived in London sometime in the 1700s, and it quickly overtook the rats that were already there. It's bigger, and it reproduces with alarming rapidity. They're liminal creatures. They come from underground. They live in sewers. They go from the light into the darkness. They cross thresholds. And they negotiate between worlds, almost like between the living and the dead. And humans find creatures like that, at the same time, fascinating and horrifying. The rats thrived in London, a dirty, chaotic city that was falling apart under the pressure of its growing population. There was really no barrier between London's sewers and the River Thames. And so you had an enormous cesspool.

And these rats, often aggressive, came into close contact with people. They bit, they attacked food stores, they made life hell. And people were willing to pay a few days' hard-earned wages to get rid of them. So Jack Black was responding to market forces. The first time I ever saw Mr. Black was in the streets of London,

at the corner of Hart Street, where he was exhibiting the rapid effects of his rat poison by placing some of it in the mouth of a living animal. Jack Black was part of a new and rapidly growing industry. Rat catchers were like blacksmiths or shoemakers, an established trade. But Jack Black insisted that he was different, that he was a self-made man. Now you might be asking, how did rat catchers work? Well, in Jack Black's case, he'd show up to the house that needed his services wearing his uniform, a gentleman's coat, top hat, and a huge leather belt bedazzled with cast iron rats. And the first thing he would do wasn't to lay traps or poison, but to roll up his sleeves.

He was able to cover his hands with lure, special bait that rats couldn't resist, that he used to catch the rats live and by hand and stuff them one at a time into a bag or into a cage. He was a kind of rat whisperer and a showman. Crowds of people would gather to watch him do his work. Women more particularly shuddered when they beheld him place some half dozen of the dusty-looking brooch within his shirt next to his skin. And men swore the animals had been tamed as he let them run up his arms like squirrels.

And this was dangerous, risky work. Jack Black got bitten all the time. And sometimes those bites made him sick. But he wasn't catching rats with his bare hands just because of showmanship or bravado. He had to catch rats alive. It was a big part of his business model. He would rescue city rats, clean them up, dry them off, and then sell them as country rats for pets or for purposes of rat baiting. City rats and country rats who lived

very different lives. Life One, The tavern basement, where rats would fight to the death. A boxing ring, but smaller. Where men sat on benches, surrounding the rat pit on all four sides. Bedding. A whistle or a bell would ring.

The rats would be released. And then a dog would be released. And the dog would have a certain amount of time to kill as many rats as possible. Life 2, the Victorian ballroom, where rats were pampered in gilded cages. They were ornate, fancy rat pets in sweet little cages, and they could be trained to do tricks. Rats are exceedingly smart, and they're actually very affectionate. Competitive rat breeding became quite popular in Victorian England and has evolved over time into an international competitive, I won't say sport, but certainly an activity. All those rats, the fancy ones and the scrappy ones,

were supplied by Jack Black and other rat catchers. It was a whole industry. And Jack Black had competition. So he had to learn how to sell his services. Like today's entrepreneurs, he was his own brand. He rode around London in a cart, handing out his advertising pamphlets that read, quote, rat and mole destroyer to her majesty. Yeah, that's right. He claimed to be Queen Victoria's personal rat catcher. Because no matter who you were, rats were a problem.

I mean, look, one of the things that makes Jack Black such a memorable figure is that he monetized vermin in a city that was overrun with them. In the process, he blurred the boundary between friend and foe, danger and comfort. So there's a very thin line separating the sewer rat from the pet rat. They will always be with us. And they are creatures that are at the same time compelling and horrifying. And I think that's why they're so fascinating. They are fascinating.

The rat, sure, but also those rat catchers. They helped rebrand an animal that for centuries was thought of as little more than vermin, synonymous with disease, into something more positive. A livelihood. A pet. A status symbol, even. A sophisticated creature that maybe has more of a place in our lives than we'd ever imagined. Does that mean I'm ready to get a pet rat? Hell no. But I can respect the hustle. For the next stop on our rat safari, we put on our white coats and head to the lab, where rats help save lives and put our morals to the test.

Hi, this is Kevin Weber from Kansas City, Kansas, and you're listening to ThruLine by NPR. Part 3. Of Rats and Men. Coming, going, always on the move. The people, the customs, even the places. In this restless, bustling city that is New York. Okay, we're back in New York City. Not today's New York, but 1960s New York.

Here, the law of the concrete jungle applies. Here, muggings and bashings are an everyday happening, be you black or white. Talk about two lives of a city. Striving to keep abreast of the ceaseless, teeming traffic of the mass of busy workers in ever-new New York. In this news report, there are shots of garbage everywhere, broken glass, and one particularly close-up shot of a dead rat. I've been sifting through old archival footage of New York, and the 1960s have stood out as a kind of turning point for humans and rats. For humans, serious fears were arising about whether

the planet was becoming too crowded. It's already happening. The threat, which is now a reality of overpopulation. What would happen if we outgrew the planet we have? Now America is a land of mighty cities. Would our resources run out? Would the social fabric fall apart? Would humans be doomed? And for rats, this was a time of reinvention. They were no longer simply vermin. They were test subjects in laboratories helping scientists develop life-saving drugs and a better understanding of illness and disease.

The relationship between rats and humans was becoming more complicated. Some people even believed rats could help answer our worries about overpopulation. So one of our producers, Victor Iveas, dug deeper into what was going on at that time. In 1960, there were 3 billion people on Earth. Just 60 years earlier, in 1900, the population was half that.

Human population was exploding. Some even called it a population bomb. And it was projected to keep growing, at a rate that was starting to seem unsustainable. A threat. Really, we're going to look at this problem as a potential catastrophe of mankind. The population explosion is just to me as serious as the atomic explosion. And among those sounding the alarm were scientists.

Dr. Calhoun is a human being. Are you worried about the future of mankind? A pathological situation like this gives us an understanding of what may be going on in the human situation, which might go on and be catastrophic. And what is really catastrophic and where the real fear is, that a scientist in Maryland named John B. Calhoun thought that the answer to our human overpopulation problems might be found with rodents. Mice and rats. By this point, rodents had been used in scientific research for a few decades

because, well, they were practically our mere images. They shadow us wherever we go. They eat very similar food than we do, which means that they're seen as very similar physiologically. And they were quickly becoming the main test subjects. But on the other hand, they're seen as vermin, which means that we are allowed to use them in an experimental setting. Experimented on to help treat things like diabetes, high blood pressure, heart disease, and cancer, and to test out new drugs. My name's Ed Ramsden, and I'm a historian of science and medicine. I'm based at Queen Mary University of London. Ed is co-writing a book on John B. Calhoun and his rats. Our familiarity

with the rat is usually based upon its living and close association with humans. There was a kind of cognitive dissonance happening. On one hand, almost all human genes associated with diseases have counterparts in the rat genome. So they're kind of like a twin of the human. But at the same time, rats were vermin, not human, creatures to be feared and exterminated. We think of sickness, disease. We think of an animal that is very unclean and aggressive. We see it as a very destructive species, even to represent sort of evil itself, the rat. So it was a balancing act. Fine to do rat experiments to test new medicines and cure diseases, but a little more iffy when it came to addressing things like the effects of overpopulation by comparing how rats and humans behave and think. John B. Calhoun was determined to change that.

You know, he's choosing an animal that is really synonymous with urban and moral degeneration. Calhoun began using rats in experiments designed to figure out one thing. What are the effects of living in a crowded environment? Which brings us to 1962 and one of Calhoun's most influential experiments. He wanted to find out whether there was a natural limit

on the growth of populations when all social order breaks down, even if all the basic needs of those populations are met, minus space. what he does is he rents a nearby barn he then divides this into four with partitions so they're into equal sizes. And these partitions are electrified, meaning that the rats can only enter and exit into the four pens through the ramps that are provided. He gives the rats as much food and water and bedding as they could possibly ever want. And he often describes his environments as rodent utopias.

The one thing they're missing, of course, is space. And as the populations begin to grow, this becomes increasingly problematic. Cajun allowed the population to grow to 80 adults, which would have been uncomfortable even if the rats spread out evenly. But because of the way the study is designed, dominant male rats took control of entire pens, pushing the rest into tighter, cramped spaces. Calhoun called these dominant males... Despots of kingpings, aristocrats. And this is where things really begin to go awry. He sees a series of pathologies beginning to emerge.

The animals become increasingly aggressive. He describes males as going berserk, attacking females, juveniles, and less active males. He describes them biting each other on the tail, which they don't normally do. He describes one group as being completely withdrawn. So withdrawn, they don't really react or communicate to any rats, male or female at all. Their coats are sleek, they look well fed, but that's because they've stopped really interacting and behaving as male rats would. Rats fight a lot. They've stopped fighting. Females suffer a great deal in this environment.

They fail to build proper nests. In time, the females stop building nests at all. So the infant mortality skyrockets to some 96% and then the infants become cannibalized by others. So it's an extremely horrific experiment in the end. There's so many problems that he's able to identify in his crowded pens that seem to plague humanity in crowded cities. Seam being the key word here. Because while yes, at the time of this study, the population was booming and cities were growing across the U.S.,

with housing projects being built to fit everyone, infant mortality rates and poverty rates were actually declining. But that perception of cities as dirty, crowded, and dangerous was strong. An influx of people were migrating from rural to urban areas, leading to a higher concentration of poverty in cities compared to the suburbs, which probably helped those perceptions stick. And Wynn Calhoun published his findings from the experiment in an essay called Population Density in Social Pathology

right below the headline of the essay, even before you see Calhoun's name. He lays it out pretty simply. Quote, When a population of laboratory rats is allowed to increase in a confined space, the rats develop acutely abnormal patterns of behavior that can even lead to the extinction of the population.

End quote. Talk about Dyer. He was sounding the alarm. Overpopulation can lead to complete collapse. And to sum it up, he coined a term, the behavioral sync, meaning a form of pathological togetherness. So for instance, violence is rampant throughout the rat pens. But because the rats are so accustomed to the presence of others, they continue to crowd together in large numbers at eating and drinking areas. They're drawn to the crowd, despite the danger it poses. Behavioral sync. You know, this is a very attractive term because it seems to capture, I think to many people reading it, one of the paradoxes of the city. You know, the city is seen as a sort of dangerous place and it's a time of

urban crisis, rising homicide rates and so on are being really reported in the news. But at the same time, as destructive as the city is, it still seems to attract us. We're drawn to it. So the behavioral sinks seem to capture something about this. The crowd is both destructive and dangerous to us, and yet we are still pulled towards it. The story Calhoun was telling about his rodent utopia turned dystopia and the cautionary tale it represented for our own human future caught fire. It was being talked about in the national press, written about in newspapers, and other scientists were paying attention. His rodent experiments were cited many times and included in a textbook called 40 Studies That Changed Psychology.

But there was one person who was starting to have doubts about this fate. Calhoun, who began rethinking his conclusions about the rat universe as time went on. He's saying, if we effectively build better environments, we can increase population density without the stress. Calhoun started to realize that the rat dystopia he observed in his study wasn't inevitable. Maybe it wasn't only an overpopulation problem. Maybe it was a design problem. Maybe you can have a similar amount of rats in a similarly sized pen and design the space differently and create a harmonious, healthy environment. So he set out to do new studies, redesigning the physical space. Trying to build environments that are less damaging to his rats, that have more partitions, that protect them from stress. So he wants to increase population density,

but without causing stress-related illnesses. Calhoun spent the end of his career trying to revise the narrative. Despite his efforts, the story of the behavioral sink is the story that people have held on to. When people think of his work, they think that it's somehow inevitable that crowding stress will emerge from dense environments, which isn't necessarily so. Calhoun died before he was able to convince the public

that we weren't necessarily doomed. His warnings of overcrowding and dense urban environments led to hysteria, and that study is still shared today. But if Calhoun had one lasting impact he'd be proud of, it's the connection he drew between rats and us, and the way he helped us see ourselves in them. This animal is so close to us, we can do all kinds of stories about them, which we have. So you think it's partly like, I don't know, we're kind of doing stories about ourselves when we're doing stories about them, you know? You know, exactly. And yet, here we have this craziness.

On one hand, we hate this animal. It's the animal we love to hate, in fact. But on the other hand, it has done so much for our benefit, for society, for our health, for everything. And yet, most people don't connect those dots. It's the same exact species. So later on, if you guys don't mind, it's Friday night. You know, the next time you're sitting, enjoying,

having a toast to say, please say thank you to our friend, Radis Novigigas. Okay. from NPR. This episode was produced by me and me and Lawrence Wu, Lane Kaplan-Levinson, Julie Kane, Victor Ibez, Skylar Swenson, Monsi Karana, Yolanda Sanguini,

Casey Miner, Kumari Devarajan. Fact-checking for this episode was done by Kevin Vogel. Thank you to Anya Steinberg, Okala Alessia, Farai Masika, Tamar Charney, and Anya Grenman.

This episode was mixed by Josh Newell. And music for this episode was composed by Ramtin and his band, Drop Electric, which includes Anya Mizani. Naveed Marvi. Sho Fujiwara. And finally, if you have an idea or like something you heard on the show, please write us at ThruLine at NPR.org or hit us up on Twitter at ThruLine NPR. Thanks for listening. This message comes from Grammarly. Back and forth communication at work is costly.

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