Allele frequency problem in “Looper”

Time travel movies are always full of bad physics and and contradictory logic, though certainly some do it better than others. I usually just try not to think about them too hard so that I can take in the entertainment value. Looper (streaming|DVD) is no exception, but the most glaring error in the movie’s science was not in the physics; it was in the biology.

The beginning of the movie tells of a new mutation, the “TK mutation”, that has crept into the population to give people weak telekinetic powers. The idea of a gene, and more importantly a mutation in an existing gene, somehow allowing telekinesis is of course absurd, but that isn’t what I’m talking about.

I’m talking about the allele frequency. The movie takes place in the 2040’s. Only thirty years from now. And, at that time, the movie says that 10% of the human population has the TK mutation. This frequency is fantastically improbable.

Why? Well, right now 0% of the human population has this mutation. The thirty years between now and then have to bring that to 10%. That sounds impossible – let’s see if my suspicion is correct.

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