Like many people, I needed a cat photo for my personal website. Lulu did the trick. She was puffy and orange and belonged to the former roommate of my sister's boyfriend. Lulu - whose nickname is Luyonce - vamped obligingly, and Lulu's owner soon decided that her budding cat model required an Instagram account.
That was just over six months ago. My website's traffic has languished, but Lulu now commands nearly 40,000 Instagram followers. "Be the cute you wish to see in this world," one post says. In another, she gloats from the bottom of a laundry hamper.
The glorious rise of my furry affiliate came as a bit of a shock, and I'm not alone in my consternation. Nobody intended for the Internet to be swarmed with cats. (Asked what surprised him most about online life, digital pioneer Tim Berners-Lee replied, "Kittens.") Yet here they are, modelling toupees made from their own discarded fur as part of the Trump Your Cat movement or popping up to protest against Brexit.
Of course, nobody intended for the planet to be swarmed with house cats either. In many ways, their online dominance is an extension of their earthly conquests, and the same flesh-and-blood behaviour that propelled cats across the globe also sustains Lulu and her peers.
A recent study of ancient feline DNA showed how cats left their native lands in the Near East, hitching rides with human seafarers - including, delightfully, Vikings - and then ditching us to invade an ever-wider array of habitats.
This is pretty much what happened on the Internet. The online community 4Chan is thought to have introduced the LOLcat (the "laughing out loud" cat) in the mid-2000s as an inside joke. But the LOLcats escaped and spread and multiplied, just like the Viking cats or Australia's colonial-era cat castaways, which have become nearly 20 million strays today.
Cats aren't the only creatures to thrive online, of course, and dogs actually eclipse them in search traffic. But their viral success is unique. According to data from Buzzfeed, the most popular cat posts get almost quadruple the traffic of the most-clicked dogs. Cat images also have unparalleled staying power. Other creature memes - the "O Rly" snowy owl, the Socially Awkward Penguin - tend to rise and fall rather quickly. But cats remain on top, pixelated apex predators whose peaks of online attention last for months or years.
Their virtual success is rooted in their real biology. Cats are solitary, asocial hypercarnivores built to do one thing: get meat. The famous cat meme I Can Haz Cheeseburger, in which a gaping grey cat demands a quarter-pounder, had the right idea. Every fibre of the feline being is evolved to hunt, and cats employ a distinctive stalk-and-ambush approach, in which they sit very still and watch for prey to innocently wander by, then explode from the underbrush to slaughter it.
This stalking and pouncing is perfect for a six-second Vine or a pithy tweet. Think of your favourite YouTube cat videos: A cat springs into a box, or bops a baby on the head without warning, or rockets out from beneath the bed. What you're watching is an ambush.
Dogs, by contrast, aren't surprise predators. Their wild relatives, wolves, are long-distance hunters, tracking prey for miles. Such dogged personalities make for better long narrative arcs, which is why canines outnumber cats in movies and novels. But the Internet is more like poetry: nonlinear, fragmented, spontaneous and explosive, a place to simultaneously hide and strike. And from Dr. Seuss to T. S. Eliot, poetry is a rare medium in which cats are more prevalent than dogs.
Cats' social habits - or, rather, lack thereof - also prime them for life online. Dogs are highly social animals, whose behaviour is such a mirror of our own emotions that without people in close physical proximity they can seem like unfinished beings.
Cats, though, are self-contained. Because cats need staggering quantities of meat, they are by necessity solitary, patrolling large tracts of territory alone. They perform best in perfect isolation, and we get almost the same satisfaction admiring a cat through a computer screen as we do from observing one lolling on our own carpet.
But what about the quintessential Internet artefact, cat photos? These portraits involve neither socialising nor violence. Yet their appeal is still connected to feline biology, through the mesmerising structure of the feline face.
As watch-and-wait hunters, cats have big, round eyes planted right in the centre of their heads, giving them excellent depth perception when they leap for a kill. They have little snub noses, since they lurk in hiding places instead of snuffling after prey for miles like dogs. And they have rounded faces and chubby "cheeks", the by-product of short, powerful jaws designed to deliver a killing bite.
These facial features, a terrifying distillation of feline lethality, happen to also be what humans consider cute. They remind us of our own faces, and especially of our babies, since humans, too, have big eyes planted in the centre of our heads, which we use in large part to read the facial expressions of others. Through this uncanny but accidental inter-species resemblance, cat faces prime us to communicate, whether by post, tweet or pin.
In nature, cats themselves aren't big communicators. Most interact with other members of their own species only when they fight or mate. Unlike group-living dogs, which have a large, expressive repertoire, cats have faces that are empty canvases, as animal behaviourist John Bradshaw suggests - strikingly human but also perpetually deadpan.
This is why cat photos seem to cry out for captioning: We feel moved to fill in their blanks.
Hello Kitty, whose popularity anticipated the success of online cats, exaggerates this beguiling blankness by having no mouth at all. But we are also transfixed by cats whose captions seem built in. Many A-list Internet felines, like Grumpy Cat, have oral deformities that make them seem to smile or grimace, as if they are furry emoticons.
Although cats were predestined for online dominance, they might have missed the boat had the Internet started a little earlier. Until the past half-century or so, most pet cats lived outdoors, and - precisely because cats are cryptic loners, and largely nocturnal to boot - we seldom saw them for extended periods. Only recently, with the advent of the "indoor cat", have we finally gained round-the-clock access, and the ability to immortalise our cornered pets' every move.
But as ever with the cat, these photos and cellphone movies give us only the illusion of control. Stranded in our living rooms but loosed online, cats slip our grasp yet again.
• Abigail Tucker is the author of the book The Lion In The Living Room: How House Cats Tamed Us And Took Over The World, from which this essay is adapted.