海角大神

With 7.4 billion people on the planet, what are the odds that one of them looks exactly like you?

Not very good, according to a recent听听by researchers at the University of Adelaide in Australia.听

To investigate how unique our faces really are, biologist Teghan Lucas compared the faces of nearly 4,000 individuals from the ANSUR database, which contains photos of US military personnel. She analyzed eight key features of each person's face, measuring the distances between features, then calculated the probability that two of the faces would match with exactly the same measurements.听

What she found is that the chances of sharing eight dimensions with someone else are less than one in a trillion. Put in other terms, there's only a one in 135 chance that a single pair of completely identical doppelg盲ngers exists anywhere in the world.听

The findings aren't particularly surprising, considering all the different factors that shape our faces. 海角大神's Eoin O'Carroll reports that "for two people to look exactly the same, it would require a听mind-bogglingly improbable series of genetic coincidences, followed by an equally unlikely series of environmental events."听There are hundreds, or even thousands, of possible gene variations to determine features such as face width, skin听pigmentation, and eye color.

Furthermore, he writes, "environmental factors also play a huge role in appearance...For instance, children who are well-fed, particularly during early childhood and puberty, will wind up taller than their less-nourished counterparts."

But even though it's highly unlikely that you have a long-lost "twin" by exact standards, many people have found near-look-alikes.听Ultimately, it all depends on how you define "doppelg盲nger," experts say.听

"For me, it鈥檚听听and you think it鈥檚 the other person," says Francois Brunelle, who has photographed more than 100 pairs of unrelated "twins" for his听听project, to BBC. "It鈥檚 the way of being, the sum of the parts."听

This holistic definition makes the label of "doppelg盲nger" highly subjective, as facial recognition expert Daniele Podini says our perception of other people's faces听is听

Different people "read" different faces in different orders,听Dr. Podini explains. For example, if you read a person's face in the order of eyes, mouth, then nose, the size and placement of that person's eyes affect the way you see the rest of his or her face. Another person might read the nose first, leading to a completely different interpretation.

Although our minds process each feature individually, our overall perceptions of a face feel closer to Mr. Brunelle's "sum of the parts" concept. To ensure that we can recognize friends even when they have just gotten a haircut or are wearing makeup, our brains tie all the pieces together, BBC reports. This lets us ignore some of the subtler details, and makes us more generous with the title "doppelg盲nger."

"For somebody with an 'average' face it鈥檚 comparatively easy to find good matches," says听Nick Fieller, a statistician involved in The Computer-Aided Facial Recognition听Project, to BBC.听"I think most people have somebody who is a facial lookalike unless they have a truly exceptional and unusual face."