Assume two isolated human communities with 500 individuals in each. If the same neutral mutation happens at the same time in two individuals, one from each community, what is the probability that it will be eventually fixed in both of the populations? How would the result change if the two communities fully interbreed? Write down the numbers in scientific notation and separate the two answers with a comma, e.g. 10-?, 3 × 10-².
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The probability that the mutation becomes fixed in each isolated population of 500 individuals is approximately 1/(2 × 500) = 10-³. The combined probability for fixation in two independent populations is thus equal to 10-³ × 10-³ = 10-?. If the two populations fully interbreed, they can be considered as a single population of 1000 people with two mutations. The fixation probability is therefore calculated to be 2/(2 × 1000) = 10-³. Hence, it is more likely for the same rare neutral variations to become fixed in the entire population in these communities if they highly interbreed.

Assume Two Isolated Human Communities with 500 Individuals in Each