Despite not owning a pet, I found myself nervously calling a veterinarian a few weeks ago.

"How many sick cats do you have?" asked the receptionist.

"Just one. There were more, but there's only one left."

"Long haired or short haired?"

"I don't know. Furry?"

"What color?"

"Calico, I think? Splotchy?"

"What's her name?"

"It doesn't have one."

"What?"

"It's a stray. I never gave it a name. I ... I didn't want to get attached." The receptionist laughed at me.

A few months earlier, I'd moved into a new apartment in Brooklyn (99-cent store Brooklyn, not artisanal coffee shop Brooklyn). Along with a backyard, my roommates and I inherited a stray calico cat and her three newly minted kittens.

They were trying to domesticate us.

We'd come outside to eat, and the patchy kittens would gaze up at us like giant googly eyes glued on cotton balls. Cats have big eyes in the middle of their round faces, useful for ambushing prey. Their noses are small because they don't rely on smell for hunting. Through a stroke of weird evolutionary coincidence, these traits remind people of human babies. It's a trick artists use all the time; despite being an ugly alien with leathery skin, E.T. was cute because he had those adorable features. Cats even have a special purr they use to ask for food that sounds like an infant crying, though these kittens never purred for me.

For weeks, my roommates and I would look away from their baby faces. It's not like we fed the backyard rats. Why should feral felines get welfare?

World domination

When humans disappear, cats will probably run the world. Iryna Kuznetsova/Shutterstock

As humans were inventing agriculture and civilization in the Middle East about 10,000 years ago, people gathered small wildcats to kill crop-eating mice, another species in the process of tying its fate to humans.

At least, that's one explanation. Some historians historians think that humans weren't particularly in control of the situation at all. Cats would come over to human settlements, and people let them hang around.

"We think what happened is that the cats sort of domesticated themselves," researcher Carlos Driscoll told the Washington Post. It seemed plausible, considering that it was happening to me.

Wherever humans went, cats followed. Cats sailed with Vikings and traveled with European colonists to the New World. When Genghis Khan was laying siege to a walled Chinese city, he promised the city he'd end the siege in exchange for 1,000 cats and 10,000 swallows. The city happily handed over the animals. The Mongols tied cotton to the cats' tails and lit the cotton on fire; the cats ran home and set the city ablaze. In the chaos, the Mongols stormed the walls and captured the city.

Humans have spent the last 10,000 years conquering the globe, and cats have come right along with us.

Today, there are roughly 160 million cats in the U.S.; about 90 million are pets while the rest roam free. There are 600 million cats around the world on every continent but Antarctica, 200 million more than dogs. That makes them the most popular recorded mammal on Earth after humans and the animals humans breed for food (mice may actually have everyone beat, but nobody seems to have figured out how to count them). Cats are doing far better than their wild counterparts; there are more tigers kept kept as pets in people's backyards than the 4,000 or so left in the wild, which is why you'll periodically read articles about tigers wandering California streets.

The only animal that orders humans around

One of the kittens in my backyard. Ilana Strauss

One day, I went outside to eat an ex-roommate's cereal like a typical stray 20-something. The single mother and her children sat at my feet, hungry peasants before a queen. There used to be three kittens, but now there were only two.

Life for street cats is tough. They deal with traffic, cold, disease and hunger. Nearly half of kittens born outside die before they grow up. I told myself that perhaps someone had adopted the third kitten, but I wouldn't have bet on it.

The remaining kittens had gotten skinny, too skinny. I reached out to touch one's silky coat, and I realized the animal was more Q-tip than a cotton ball, all fur, no muscle. The kitten wiggled away, but her mother kept staring at me. Their deaths will be on your hands.

"Just a minute," I said aloud.

I walked to the corner bodega and slunk down the aisles, past the canned beans and old oranges, until I found what so many sentimental pushovers like me must have found: cat food. Each can advertised "real meat," so you knew they hadn't secretly invented laboratory meat and used it exclusively for cats. I handed two cans to the cashier, head down, wondering if he realized the cats had won. Then again, he probably already knew; this deli also had a cat. I felt like I was joining some sort of pathetic secret society.

I opened a can in the backyard and dumped out a spongy pink blob of what was once a tuna fish living a regular tuna fish life. Tuna are endangered; cats are overpopulated. Pet cats and dogs eat about 25 percent of the meat consumed in the U.S. and as many calories as the entire population of France.

The mother reached the tuna first but stood back, waiting for her children to eat. The kittens tore in like starving prisoners. It was the beginning of the end of human dominion over the backyard.

Not quite tame, not quite wild

The mother cat keeps watch as her kitten eats. Ilana E. Strauss

It's easy for me to understand how humans relate to most other animals. We are generally bad news for wild animals; since the 1940s, wild animal populations have been cut in half in what scientists are calling a mass extinction thanks to habitat destruction, hunting and pollution. Domestic animals are basically slaves; cows, chicken and sheep are treated like food-producing machines. Even dogs are loyal servants.

But cats? Cats are different. They don't have social hierarchies, making them pretty bad candidates for domestication since they won't follow orders (and often tell us what to do). Yet they're doing very, very well in this human world of ours, largely because we just like them so much. In many ways, they're the most prosperous predators of our time, capable of both hunting and getting people to do their bidding.

Once I started feeding the cats, my roommates, who had been eyeing the adorable strays as long as I had, quickly followed suit.

"We're like a bunch of childless 30-somethings," said my roommate. Yes. Like that. Except unlike human children, these cats didn't even pretend to like us.

When I'd reach toward the kittens, they'd spring back. That is, unless I had food. Then they'd jump up onto my picnic table and attack my lunch until I hissed at them. When you train an animal, it learns to understand "sit," and "stay." When a wild animal trains you, you learn its language.

You're a mammal, I'd implore a kitten. You like touch. Why won't you let me pet you?

Some pet cats nuzzle up to you even when they're not hungry. But these strays were a different breed. I was just a food-dispensing machine to them. Eventually, I felt more and more cheated. I watched you grow up. I fed you. Get on board with the human-pet agreement!

The truth was that these cats didn't really need me. Cats can survive perfectly well on their own just about anywhere. I once spent a couple weeks with hunter-gatherers in the Amazon who had brought cats and dogs into the rainforest. The cats looked well fed, boasting sleek coats that suggested flawless health.

Cats doing just fine in the Amazon jungle. Ilana Strauss

The dogs, on the other hand, were a mess. They'd forgotten how to hunt, and so they waited for scraps, mangy and bony, ribs sticking out. They looked like they belonged in a heroin den.

Golden retrievers, pugs, poodles and most other dogs look nothing like the wolves they evolved from. That's because humans have bred them for thousands of years, turning them into devoted minions far better at pleasing humans than hunting. Dog breeding has been going on for so long that dogs are a bit like a European royal family; that's why Dalmatians are often deaf and pugs have trouble breathing. Here, on the other hand, is an African wildcat, the Middle Eastern desert animal that all domestic cats evolved from:

These guys still breed with domestic cats all the time. Ecoprint/Shutterstock

I couldn't pick it out of a line-up of housecats. Domestic cats look almost exactly like their wild brethren, and that's because humans haven't bred them all that much over the millennia. Unlike most domestic animals, domestic cats are just as genetically diverse as wild animals.

"In contrast to almost every other domestic animal, cats retain remarkable control over their own lives," wrote John Bradshaw, a professor at the University of Bristol. "Most go where they please and when they please and, crucially, choose their own mates."

It's hard to distinguish between feral cat, stray and housecat. Technically, a feral cat is a cat that doesn't like people, which I supposed means a feral human is a human that doesn't like cats (they call themselves "dog people"). Strays are abandoned pets. But it's really a spectrum; a cat can be born a pet, become a stray and go feral as it gets older. Street cats aren't a modern scourge or outgrowth of abandoned pet cats. It's the other way around; street cats came first, and indoor cats grew out of them. In fact, indoor cats used to be rare; even pet cats lived outside.

"Back in [President Calvin] Coolidge's day no one thought of confining cats indoors — not even one belonging to the president of the United States," wrote Sam Stall, author of "100 Cats Who Changed Civilization." That state of affairs lasted from ancient times until the end of World War II.

The bag of dirt that changed everything

Kitty litter was invented by accident. Cristina Negoita/Shutterstock

It was 1946. The second World War had just ended. Frank Sinatra was releasing his first studio album. The bikini was debuting in Paris, though it wouldn't reach Americans for another decade or two; they were busy inventing nuclear weapons instead. And the human-cat relationship was about to change forever, thanks to a bag of dirt.

Edward Lowe, who was 27 at the time, was working lugging around ice and sawdust for his father in Michigan. His neighbor asked if he had any sand for her kitty litter box; very few people had litter boxes back then because sand and straw just don't work very well. Lowe suggested trying out some extra clay grounds he had in his car. The clay worked so well that he tried to sell it at a pet store.

"Everyone laughed at my idea in 1946," Lowe told The Chicago Tribune. "‘Dirt in a bag,' they said. ‘Who will buy dirt in a bag?'" Millions of people, as it turned out. Lowe ended up leading a $350 million kitty litter industry. He become a multimillionaire with 22 houses and a 3,000-acre estate.

"Don't call it an estate. It's a farm," growled Lowe on what must have been a weird day for that Chicago Tribune reporter.

Lowe had an art gallery full of photos of himself and a golf course with car-sized pickle vats instead of holes. He once took a liking to some heavy stone slabs from an old jail that were lying on his friend's lawn. The slabs were too heavy to move, so he just bought the lawn. He called himself a "typical American entrepreneur" and would say things like: "Anyone who wants to be a millionaire can be one."

"Ed Lowe can do something very few people can do. He can live his total fantasy," remembered Lowe's former coworker "fondly."

Thanks to kitty litter, indoor cats are now common, but this is new. Unlike dogs, cats still have not traded in their independence. Their lives are their own. And that's largely because they still know how to hunt.

Apex predators of the backyard

A kitten eats the salmon scraps we left out for her. Ilana Strauss

One summer night, as Christmas lights cast an eerie glow over our backyard, my roommates and I saw something odd. The mother cat crouched at the edge of the yard, watching her playing kittens. Then she leapt across the patio and pounced on her daughter. The mother raised her paw, claws outstretched.

My roommates and I stopped talking and stared at the strange scene. It seemed impossible; the mom couldn't really be attacking her children, could she?

Then the mother tapped the kitten with her paw and walked away like nothing had happened. "She's teaching them to hunt," realized my roommate.

From that day on, I'd frequently see a kitten crouch in the weeds like a tiny lion, then pounce on her unsuspecting sibling. I'd always assumed that hunting was pure instinct. But apparently, cats have to learn how to do it.

I got the feeling that, if humans disappeared tomorrow, cats would take over the world. There are millions of them, and they're master hunters.

"If we were in an apocalypse, the dogs would perish and cats would flourish," Wesley Warren, a genetics professor at Washington University studying how cats spread around the world, told me.

When humans come into a new area, they get rid of all the larger animals, and cats take care of the smaller ones. American cats kill off 12.3 billion mammals and 2.4 billion birds a year, leading some to suggest trap-neuter-release programs, while others demand death for every feral cat. So naturally, a war has sprung up between cat lovers and bird lovers.

In 2011, Nico Dauphine was not happy with her new apartment. She was a Smithsonian Conservation Biology Institute research fellow and bird lover who wrote about the dangers of invasive cats, and she'd just moved moved to D.C. to study how cats predate on birds. Ironically, the area outside her new building was full of feral cats.

Dauphine noticed that an old woman in her apartment often left kibble under the bushes outside; skinny feral cats would come over to eat it. So she sent an email complaining about the cats to the building's management.

"Please do keep my name in confidence," she wrote in the email, "as I know from experience how emotional people can get from these types of situations."

Soon after, the neighbor found a mysterious white substance on the kibble. She called the Humane Society, who tested it: It was rat poison. Grainy security footage spied Dauphine, wearing a striped winter hat and coat, going over to the cat food and taking something out of her bag. The cats were fine, but she was charged with animal abuse. Her case was a high-profile one, but it wasn't unusual; similar accusations about cat people and bird people abound.

The case turned into a massive media scandal. Dauphine hired Billy Martin, the celebrity lawyer who had failed to save Michael Vick when he was charged with dogfighting, which in retrospect seems like a terrible strategy. She lost the case and had to flee the city, followed by death threats.

Everyone has a weakness

The kitten that eventually got sick. Ilana Strauss

Unlike the cats Dauphine allegedly tried to poison, one of the kittens in my yard, the alpha, was getting sick. She wandered into our yard one day looking like a used Q-tip; the other cats and I looked over. She padded to her mom, who hissed and swiped at her. I imagined my mom turning me away with a hiss.

We continued to watch the sick kitten suspiciously until she wriggled through a hole in the fence and into another yard. I realized that, for all my judgment, I was no different than the mom. For all intents and purposes, I was just another cat, and I didn't want a diseased animal coming near me either.

"Can we take it to a vet?" asked my roommate.

"If you want to take it."

The healthy kitten was alone now, her mother having dubbed her adult enough to make it on her own, and her sister fallen prey to illness. She started spending the days sitting on an old desk propped against the backyard wall, nestled against a bag of charcoal. She didn't play anymore; she just sat there, waiting for whatever a cat waits for when her family is sick, dead or has abandoned her.

It rained a couple weeks later. All the other cats were staying dry under a balcony, but the sick one just wandered through the rain like a ghost, seemingly obvious to the water. It walked over to a puddle, tried to lick it, then got confused and ran away.

The healthy kitten and I watched it from the desk. Like someone awkwardly comforting the bereaved at a funeral, I reached over, expecting that the healthy kitten would, as usual, jump away when I came close enough. But she didn't move. I ran my hand across her satin back, feeling her delicate bones. She looked up at me with her murky green eyes. My hand began to vibrate. She was purring.

A love-hate relationship

Some people associate black cats with witchcraft, and other people think that cats carry bacteria that control human minds through a disease called toxoplasmosis. GeorgySar/Shutterstock

Humans have had a love-hate relationship with cats for millennia. Ancient Egyptians worshiped cat gods and decorated vases and artwork with images of cats. When a household cat died, the family members would shave their eyebrows in mourning. Today, cat lovers are ubiquitous online. One Japanese train station even made a cat its stationmaster in 2007, complete with a little conductor hat and badge.

But Medieval Europeans considered cats demonic. One story in the "Malleus Maleficarum," a well-known book on witchcraft published in 1487, describes a man chopping wood who was suddenly attacked by a bunch of cats. He beat them back, but he later was thrown in a dungeon, accused of beating townswomen. The man claimed he'd hit cats, not humans, and the town's authorities were all, "Ah, of course, the devil must have turned them into cats."

"They released the poor man and let him go away unharmed, telling him not to speak of this matter to anyone," reads the "Malleus Maleficarum," which seems suspicious. If the devil were turning people in my town into cats, I'd want to know.

The Belgium town of Ypres celebrates an annual tradition in which people throw stuffed cats off a church. In the old days, they threw live cats.

"Not many Americans know about Danish holidays," chirped the Danish Museum's article explaining the tradition.

When royalty came to one Belgian town, the town celebrated by bringing a beautiful ship to the town square, filling it with cats and fireworks, and letting the sounds of cracking explosions and meows fill the town. Pope Innocent the Eighth ordered the Inquisition to burn all cats and cat lovers to spread godliness throughout Europe. I don't know how much godliness he spread, but he did successfully spread something: rats, finally free of their predators, infected Europe with the bubonic plague.

Halloween decorations still feature witches with their cats, and movie villains sit in swivel chairs, plotting world domination while stroking their pet cats. Some think that cats carry bacteria that control human minds through a disease called toxoplasmosis.

"I think that the fact that we have glommed onto this idea, and we write so many stories about it, speaks to the fact that cats do have some kind of mysterious power over humanity," explained author Abigail Tucker in an interview. "These stories about toxoplasmosis remind me of stories that used to come out six or seven hundred years ago about cats and sorcery — that cats have dark powers we don't understand, that they're witches in disguise."

The last kitten

The last kitten in my backyard wasn't looking so good. Ilana Strauss

The backyard cats indeed seemed to have me under their spell. I hadn't seen the sick kitten or mom in days, so I crept outside one night to find the last kitten, as always, cozying up against the charcoal bag. I cracked open an egg and offered it to her, but she uncharacteristically ignored the food. Something was wrong.

I read online that it's important to keep sick kittens warm, so I grabbed an old T-shirt featuring fading "South Park" characters and wrapped it over her. After further online medical searches, which are never a good idea, I found a disease that seemed to fit her symptoms. The prognosis was death.

The next day, I called the vet and made an appointment, which meant my roommate Anna and I needed to bring the kitten to the vet somehow. First, we tried putting her in a plastic bucket covered by a towel. She kept hopping out, so we went to the pet store to pick up a cat carrier, which is apparently a thing. The carriers were all really expensive.

"Maybe we can just put her in a cardboard box," I suggested.

"You can't put a cat in a cardboard box!"

"... Can't you?"

"Excuse me," Anna said, addressing a 20-something man who worked at the store. "My friend and I are deciding whether we should carry our cat in a cat carrier or a cardboard box."

The man thought about it.

"Cardboard box," he said. Anna was stunned.

"Like ... like a special kind of cardboard box?" she asked.

"Sure, we have those," he replied, pointing to a cardboard box on a shelf for $16.99.

"Is that any different than a regular cardboard box?" I asked.

"No."

We found an old cardboard box on the side of the street. Anna picked the kitten up and dropped her in, and I rapidly tried to tape the box closed. The kitten sat confused for a few seconds, then leaped out. We tried again; this time she scratched me. As cherry apple blood oozed from my finger, the kitten and I stared at each other, both in uncharted territory.

We finally got her in and took an Uber Pool to the animal clinic, Anna holding the box on her lap. A meow came from the box, and the other passenger looked over.

"We're going to the vet," I said.

"We've got a stray cat!" exclaimed Anna.

The passenger turned away and kept her eyes forward the rest of the ride.

She actually got pretty used to the box. Ilana Strauss

I was expecting a typical doctor's office — modern, spacious, sterile — but the animal clinic looked like an abandoned storefront that someone was using as storage space. Boxes filled the single, narrow room; an obese cat perched on the counter.

"I'm the one with the cat that doesn't have a name," I told the receptionist, who directed me to the single patient room: a cubicle next to the front desk.

As it turned out, the kitten was fine. She had worms, fleas and a bit of a cold, but that's apparently pretty normal for street cats. The doctor injected her with a special, pricey medicine to get rid of the worms.

"She'll probably just reinfect herself though," the vet said. When we got the total bill, Anna and I looked at each other like mice surrounded by cats. We paid in a stupor. At that moment, I knew we wouldn't be adopting these kittens.

Still, we spent the Uber ride home coming up with names.

"Mew Ze-dong."

"Stalincat."

"How about Princess Caroline?"

"That's too proper."

"That why it's perfect though. She's not fancy, but she's in charge."