How Cats Evolved to be Pets

Y’know cats? Tiny, cute, kind of stupid, allow you to live in their house and feed them and pet them? They don’t act like they’re in charge for no reason. According to science, they actually are!

As a supervillain, I have a right hand cat I’m required to stroke nefariously when someone comes into my office and I dramatically swivel my chair around to face them. Then he meows in approval after I say something evil. And when I say “required”, I mean he’ll probably murder me in my sleep if I don’t. He’s a good boi though. His name is Felis. ¹Felis is a tabby, but I’m too lazy to draw the stripes

By the way, this article is about several topics relating to cats, such as their self-directed domestication, how they are more genetically diverse than dogs, their evolution as predators, and their association with a parasite that can mind control mice.

Table of contents:

• Cat Origins
• Pet Diversity Paradox
• Cats are Vicious Predators
• Toxoplasmosis Mind Control

Cat origins

You may think that humans domesticated cats like how we did with dogs, horses, cows, etc. Y’know, we kidnapped some of them and raised them and selectively bred them until they were more friendly. 

But no, genetic analysis shows that selective breeding cats for appearance didn’t really start until the 19th century.

The only major difference between house cats and north African wildcats, besides all the crazy fur colors ²genetic analysis has shown that the markings of tabby cats didn’t exist as recently as the Medieval era!, is that house cats retain their kitten behaviors even in adulthood. That’s it.

It’s not like dogs who’ve been twisted into a completely different, outright manic, psychology from that of wolves. All it took to turn cats from wild animals to loving companions was becoming a man child. A single mutation. 

Early on, farmers in the Middle East and Egypt ³House cats originally evolved in the middle east. So if you ever wonder why your cat spends so much time curled around anything warm, it’s because your house is freezing to them. Their ideal room temperature is an average day in Egypt.would tolerate wildcats on their farm because they were good at killing mice that ate their grain. Same reason why farmers let barn owls live in their barns. But other than that, they didn’t have much of a relationship with cats. Cats were shy, solitary predators.

But over time, mutant manchild wildcats would start acting all cute around the farmers. They would do kitten things like meowing, the feline equivalent of a baby crying for food or attention. ⁴a cat’s meow is at the same frequency as a baby’s cry, and actually triggers the same instinctual response to help and protect in human adults as crying. Normal wildcats are solitary predators, but kittens prefer being around others and are more playful.⁵though they aren’t specifically adapted to it, which is why cats often come off as rude.

Farmers, being humans with souls, had their hearts melted by the cute cats. They let them live in their houses and started feeding them and petting them. 

Obviously, a reliable source of food and shelter is a pretty significant advantage over not having that. So the mutant man-child cats were much more successful than normal mature adult cats. Soon the man-child gene spread through the population until man-child house cats outnumbered the wildcats.

The newly evolved housecat subspecies quickly spread across the world. Framers from the furthest corners of Asia to Europe couldn’t get enough of these adorable little mouse munchers. 

Pet Diversity Paradox

On average, only about 0.1% of dog DNA differs between breeds. That may seem like a lot if you know that only about 0.01% of DNA differs between any two humans on average. But for cats, about 0.4% of their DNA differs between breeds! 

How could cat breeds be so much more genetically diverse than dogs when dogs look way more diverse? How can a chihuahua and a pug be more closely related to each other than a calico and a tabby cat?

This is called the “Pet Diversity Paradox”. But it’s not really a paradox. I mean, it’s really just something that’s counter intuitive, not an actual logical paradox. But it isn’t even all that counter intuitive if you think about it. 

Of course dogs have less genetic diversity than cats. Dogs are all horribly inbred from hundreds to thousands of years of selective breeding and maintaining pure breeds. 

Meanwhile, we haven’t really even begun selectively breeding cats until the 19th century. And even then, we mostly just do it for appearance or personality. Not for crazy superpowers like the husky’s infinite endurance, borzoi’s speed, or the dachshund’s continuing evolution into a worm.

Plus, domestic cats tend to have more gene flow from various wildcat species than dogs. Dogs can interbreed with wolves and coyotes, but the result of this unholy union never makes a good pet. In fact, in many places I don’t think it’s even legal to keep a wolfdog or a coywolf as a pet. So dog breeds aren’t getting any new genes from other species. 

Meanwhile, domestic cats can interbreed with African wildcats, European wildcats, jungle cats, lynxes, caracals, bobcats, small Asian leopards, etc, and the result is nearly indistinguishable from a normal house cat. Remember, the only meaningful genetic difference between a domestic cat and a wildcat is that domestic cats act like kittens. So as long as the hybrid got the man-child gene, you’re good. So hybrids often get back into households and the wider cat genepool. In fact, several famous cat breeds specifically are the result of hybridization, such as the Bengal cat or the toyger.

Cats are Vicious Predators

Before they evolved to be adorable social parasites, wildcats were (and still are) extremely proficient predators. As small predators, they not only need to worry about feeding themselves but also avoiding getting eaten. They evolved extreme levels of stealthiness so they can sneak up on prey and hide from larger hunters. 

The best way to judge how good a predator is hunt success rate, or what percentage of hunts the predator attempts actually results in a kill. By this metric, cats are actually pretty good at 32% success rate. This comes from an Australian study where scientists haphazardly attached some cameras and GoPros onto feral cats and watched them do their thing. 

I would just like to make it known that the authors of this study reported names the cats, such as Diddles, Sophisticat, Bazza, Captain2, Eyegore, Ginja Ninja, Jaws, Pork Noodle, and Mike.

Now, you may be thinking, 32% isn’t that much. It’s less than half. And you’d be right, that is less than half. But you’re also wrong, so shut up. For reference, tigers only have a success rate of 5-10%, so 32% is good. And it can be as high as 70% if the hunt takes place in an open environment.

Judging how good a predator is is of course subjective. And to be fair, this probably isn’t the best metric. After all, the predator with the highest success rate is the leatherback sea turtle at 100% because it exclusively hunts almost completely immobile and defenseless jellyfish. 

Plus, this study was conducted in Australia where cats are an invasive species. The things cats hunt in Australia probably aren’t as good at avoiding them as are prey in the middle east where cats originate from.

But it makes sense that cats would be reliable hunters. Again, being that they are both predators and prey, they need to spend as little time hunting as possible. The reason why cats like to sit inside boxes and sleep all day there is because they evolved to spend the majority of their time hidden.

Toxoplasmosis

There is a parasitic protozoan that lives in the GI tract of cats called Toxoplasmosis gondii. Don’t be misled by the name, T. gondii is not about to go on any hunger strikes for the sake of peace, that’s for sure. Toxoplasmosis primarily lives in and can only reproduce inside the digestive tract of felines. You might already see a potential issue with such a lifestyle I’m not going to spell out for you. What happens if a toxoplasmosis protozoa finds itself outside a cat?

Well, with any amount of luck after being ejected from the cat it will find itself inside a mouse. I’ll let you use your imagination as to how that would happen. And well, cats eat mice, so that would be the toxoplasmosis’ ticket back home!

But if you’ve ever seen Tom and Jerry, you’d know there’s no guarantee any given mouse will actually get eaten by a cat regardless of how many hijinks they use. But, what if the toxoplasmosis could make Jerry a bit less wily? A bit less cautious? A bit more risk taking? Well, it’s not so uncertain then.

Toxoplasmosis causes mice to be less afraid of cats, in particular the scent of cat urine, making it easier for cats to catch and eat them. In this way you could sort of argue that toxoplasmosis is symbiotic with cats. While the cat does get a little sick after eating the mouse, they still get the mouse, and for far less effort than they normally would. It’s basically a free meal. Not to mention, it might also be helping cats to get humans to do their bidding.

Toxoplasmosis alters behavior through several mechanisms. Toxoplasmosis produces a precursor of dopamine, phenylalanine, as well as an enzyme involved in making dopamine, tyrosine hydroxylase. All the extra phenylalanine and tyrosine hydroxylase leads to increased levels of dopamine during the Toxoplasmosis infection.

You may know dopamine as the “happy hormone”, which isn’t technically true. That’s serotonin. Dopamine is the “motivation hormone”. It’s the thing that motivates you to do stuff by rewarding your brain whenever you do something. Which is basically anything. Not having any dopamine would leave you paralyzed, so it’s pretty important. But too much is also bad, ADD/ADHD are likely caused by overproduction of dopamine.

Toxo also causes permanent behavioral changes, even after clearing the infection, by permanently turning genes on in your brain which code for vasopressin. Vasopressin does a lot of things, but in the brain it regulates some social behaviors.

There is some evidence that there’s a correlation between toxoplasmosis infection and risk taking behavior in humans. But all that said, the science is still out on to what extent toxoplasmosis affects the behavior of humans. It can infect humans, so be careful when cleaning your cats’ litterbox. But it evolved to infect cats and mice. There is a lot of commonality between how the brains of humans and mice work, but obviously it’s not one to one.

I mean, I’m practically always in contact with my cats and I turned out fine. I’m only a mad scientist with an unhealthy obsession with cats, ADD, and self destructive risk taking behavior on account of being a villain.

Addendum

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McGregor, H., Legge, S., Jones, M. E., & Johnson, C. N. (2015). Feral Cats Are Better Killers in Open Habitats, Revealed by Animal-Borne Video. PLOS ONE, 10(8), e0133915. https://doi.org/10.1371/journal.pone.0133915