If you’re looking for someone who looks precisely like you, the odds are infinitesimal. In 2016, Teghan Lucas of the University of Adelaide explained to the BBC that there was a 1 in 135 chance of even a single pair of doppelgangers existing in a population of 7.4 billion people. However, given sufficient time, it would happen. In that sense, it’s akin to the infinite monkey theorem. If you sit a monkey in front of a typewriter and let it bang away at the keys forever, it will eventually hammer out the Complete Works of Shakespeare. Similarly, if humans do a different sort of banging and make babies, over time you get a case of monkey see monkey duplicate.

If you loosen the definition of doppelganger to allow for slight physical differences, the odds get a lot higher. Generally speaking, your eyes don’t focus on fine details when processing faces, so there’s a good chance that you will see two biologically unrelated people as looking like twins. That may help explain why there are so many instances of seemingly immortal celebrities and public figures, like climate activist Greta Thunberg, who, as reported by the CBC bears a striking resemblance to a girl in an 1898 photo taken in the Yukon during the Klondike Gold Rush. And let’s not forget how a photo from 1870 ignited rumors that Nicolas Cage is a Civil War-era vampire. So depending on how you see it, you’re either one in a million or a dime a dozen.