5
votes

enter image description here

I've heard it said more than once that everyone has an evil twin out there somwhere.

By "evil twin" I mean someone who is non-genetically related but bears a striking, (I realize that term is subjective but try to work with me) if not identical resemblance to ourselves. Of course, they don't necessarily have to be evil.

For fun, websites like this are using facial recognition software to compare the faces of their users to those of celebrities.

  • What is the likelihood of two random, unrelated people sharing identical features? Has anyone studied this?
  • Have there been documented cases of this occurring?
  • I'm sorry, is this april 1st? :-) – Lennart Regebro May 18 '11 at 8:20
  • @ Lennart: while this question may seem silly, it's perfectly in place in skeptics.SE. Please tell exactly what you think is wrong with it, if you think there is anything. Even if the alleged problems with the question seem obvious to yourself :) – user288 May 18 '11 at 9:22
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    Photographer Francois Brunelle has a project in this regard: examples. – Oliver_C May 18 '11 at 9:32
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    @Sejanus: Problem #1: You haven't defined what "identical" or "striking" resemblance means. It could be quite loose or very tight, making the answer different. – Oddthinking May 18 '11 at 16:31
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    @Sejanus: Problem #3: There is no claim here. You start by talking about (the fictional trope of) "evil twins", and then discard the evil requirement and the twin requirement, to leave a vague statement that no-one claims is true. – Oddthinking May 18 '11 at 16:36
3
votes

What is the likelihood of two random, unrelated people sharing identical features?

To start off, it's kind of hard to answer since you didn't define "identical". A good definition would probably use terminology/methodology from image/facial recognition software world.

Having said that, I will assume common cultural understanding of the term (e.g. look-alikes and Doppelgängers):

For "evil" connotation, see http://en.wikipedia.org/wiki/Doppelg%C3%A4nger

For simple resemblance, http://en.wikipedia.org/wiki/Look-alike

Have there been documented cases of this occurring?

Again, for "evil" twins: http://en.wikipedia.org/wiki/Doppelg%C3%A4nger#Notable_reports

For simple lookalikes, Wiki has a hilarious example:

  • During the 1920s, Charlie Chaplin once went to a Charlie Chaplin-look-alike competition. Chaplin didn't even make it to the finals. (source: Howell, Melissa; Howell, Greg; Pierce, Seth (1 August 2010). Fusion: Where You and God Connect. Review and Herald Pub Assoc. p. 275. ISBN 9780828025478)

  • Another notable example, though to be honest they don't look all that similar to me:

    Paul McCartney and William Shears Campbell

  • And here's Stalin's body double

    enter image description here

1
vote

Even identical twins don't share the same features exactly; there are developmental differences. And the chance of being genetically identical-enough is vanishingly small; hundreds of genes affect appearance, so even multiple (non-identical-twin) children from the same couple don't look that much like each other.

So, given that a genetic match is out of the question, is there some chance that we just can't tell that many people apart so that you will have a very very close look-alike somewhere? Celebrity look alikes provide some data as to how alike people look. There is no particular reason to believe that celebrities are more or less likely to have look-alikes than anyone else, and there is strong pressure to find celebrity look-alikes, so this gives a reasonable estimate of the level of similarity one should expect.

There is also research into the dimension of "face space"--that is, in how many independent characteristics can faces vary? The answer, according to both psychology and modeling, is in the range of 100-200. Since there are so many independent characteristics, the chance that two unrelated people will share essentially all of them is vanishingly small.

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