Part of why these awesome folks are able to find so many lookalikes is the fact that the term itself is pretty loose. As mathematician David Aldous, formerly of Berkeley, explained to Discover Magazine, to even attempt a quantitative calculation of whether everyone has a doppelganger requires two things — a precise definition and real data — "and neither is easy to do."

If we take Twin Strangers, a website that promises to find your lookalike using facial recognition software, as the basis for our 'study', there are at least 9.3 million doppelgangers in the world.

However, by some estimates as many as 100 billion people have walked on Earth—the dead far outnumber the living. Considering that many more humans will come after us (fingers crossed), I'd say our individual chances of having a doppelganger are pretty high. But whether or not we'll meet them is a totally different thing.

Interestingly, there have been quite a few attempts—like this one by a team of Australian researchers—to calculate the odds of you having a living doppelganger.

In the above-mentioned study, scientists said it's less than one-in-a-trillion, though Aldous thinks how they came to that number is “quite dubious.” The study looked for exact doppelgangers, which means they're more similar to one another than identical twins. Humans simply don't recognize each other like that.

The human face is made up of several attributes — the nose, eyes, eyebrows, jaw, cheekbones, and so on — that are measurable and governed by genes. While the number of possible human faces is perhaps a theoretically knowable figure, the simple fact is that nobody today has any idea what that number might be, geneticist Walter Bodmer explained.

In The Human Inheritance: Genes, Language, and Evolution, Bodmer said one of his research goals was to recreate a face from DNA. And there's work currently being done to recreate the faces of our long-extinct cousins, the Denisovans.

If there's one thing we can be sure of it's that facial features are considered to be highly heritable.

Research also suggests that there are relatively few genetic variants associated with the shape of the face, "or features wouldn't be as heritable as they are," Bodmer said. "If you found enough [genetic variants] to explain the genetics of every face, that would be your objective measure of the variations."

The geneticist highlighted that the more of these genetic variants people share, the more similar their facial features will look. But he isn't sold on the idea of complete lookalikes.

"I think to turn it into a mystique of doppelgangers is a mistake, and I don't think we have the data to tell us," Bodmer said. "Every picture I've seen, I could tell the difference between them." Doppelgangers, pretty much as a rule, only catch people at first glance."

So, does each and every one of us have a doppelganger out there now? Or is there one lurking in the past or waiting in the future?

"Probably everyone has one, at a glance," Aldous said. "The fact that you see it happening to other people means you know it’ll happen to you. At first glance, I’m sure that happens to everybody."