Cats may not be man’s best friend, but they’re arguably something even better: man’s key to instant Internet pageviews. It’s a long-established fact that Internet content—whether it’s a cutesy video, a photoshopped inside joke, or a longform public health article—has a better chance of achieving coveted “viral” status if it somehow evokes the sound of purring.

But if we’ve come to accept that cats play an outsized role on the World Wide Web, our understanding of why that’s the case still lags. Most of us would simply plead that we happen to think of cats, and their various digital reproductions, as “cute,” but the sheer magnitude of their popularity suggests that there’s something more than a purely subjective phenomenon at work. Fortunately, natural and social scientists have managed to shed some light on the mystery.

The first thing to acknowledge is that there was a deep interest in cats long before there was an Internet. Miles Orvell, a cultural historian at Temple University who specializes in visual culture, said that what the Internet has done is leverage a preexisting fascination. “There’s a contagious effect of the Internet where something that is there as a latent possibility can emerge at large in society,” Orvell said. “It’s not so much creating this interest in cats, it’s more exploiting this interest that was already there.”

Orvell pointed out that Western culture’s interest in cats extends as far back as the ninth century, when an Irish monk wrote a poem about his cat called “Pangur Ban.” It would prove a lasting trope. Nine-hundred years later, Christopher Smart would write the poem “For I Will Consider My Cat Jeoffry”; in the 1930s T.S. Eliot wrote his famed Old Possum’s Book of Practical Cats, which later became the basis for the musical CATS. Outside of literature, cats became a staple of American popular imagery in the twentieth century, from television advertisements to Tom and Jerry. Cat videos on the Internet that garner millions of hits, Orvell says, should be thought of as an animated extension of the cat calendars of yesteryear.

But why have cats specifically been so successful at soliciting our attention? One hypothesis is that there is a fateful link between cats and human babies that explains their Internet stardom. According to Michael Newall, a philosopher of art at the University of Kent, our inordinate interest in cats may derive from their formal resemblance to our offspring—their big eyes, smallish noses, and dome-shaped heads trigger the evolutionary nurturing instincts that we have evolved toward babies. There may even be a multiplying “superstimulus” effect at work: Newall posits that the exaggerated proportions of cats’ baby-like features prompt an exaggeratedly intense, and involuntary, response in people.