I think I've read that in humans, it takes either 50,000 or 100,000 years for a mutation to fixate. But I've looked into the books I thought it mentioned it and I can't find it. I know there are theories that behavioral modernity has arisen before 40,000 years ago, and that modern humans evolved from Homo heidelbergensis, Homo rhodesiensis or Homo antecessor, some 100,000 to 50,000 years ago, but I don't know if this implies the same. Anatomically moderm human . On the other hand, this other article (7 years old now) says evolutionary change might take 1 million years (Not so fast).

How much time takes for an evolutionary change to take place in animals in general, but also in humans in particular? (if there is any difference between humans and the rest of the animals. I know mutations don't take the same time to spread in animals than in bacterias, for example)

  • $\begingroup$ I think the term you're looking for is "fixation". The fixation of a mutation is its presence in a population with frequency =1, that is every individual of that population has that mutation. $\endgroup$ Commented Jan 19, 2018 at 15:36
  • $\begingroup$ Are you arguing that it took 50,000 years for humans to cause the extinction of the Carolina parakeet? Or that it takes 50,000 years for XDR tuberculosis to become common? $\endgroup$
    – swbarnes2
    Commented Jan 19, 2018 at 17:21
  • 4
    $\begingroup$ Any change in allele frequency is considered an "evolutionary change". So, you don't need anything to fix to get an evolutionary change. $\endgroup$
    – Remi.b
    Commented Jan 19, 2018 at 17:43
  • $\begingroup$ But it seems not everybody uses it in that way, my question goes in the sense it is used in this link regardless of semantics. phys.org/news/2011-08-fast-evolutionary-million-years.html . BTW, I've also seen it used that way it's used in the link, in a book $\endgroup$
    – Pablo
    Commented Jan 19, 2018 at 17:45
  • $\begingroup$ @Pablo well this popular article is awfully phrased! I can't really judge the content otherwise as the popular article fails to link to the original research paper from which they supposedly report the results. $\endgroup$
    – Remi.b
    Commented Jan 19, 2018 at 17:54

1 Answer 1


How much time does it typically take for a new mutation to fix in an animal population?

The answer can really take any number. It will all depend upon the size of the population and the selection coefficient on the mutation. If we assume neutral mutations, then we can use Kimura and Ohta (1968)'s result. They showed that the expected time for a neutral allele to reach fixation (given that it will reach fixation) is

$$\bar t(p_0)=-4N\left(\frac{1-p_0}{p_0}\right)\ln(1-p_0),$$

where $p_0$ is the initial frequency and $N$ is the population size. Replacing $p_0$ by $\frac{1}{2N}$ and you get

$$\bar t\left(\frac{1}{2N}\right)=-4N\left(\frac{1-\frac{1}{2N}}{\frac{1}{2N}}\right)\ln\left(1-\frac{1}{2N}\right)$$

which can be simplified

$$\bar t\left(\frac{1}{2N}\right)=-4N\left(2N-1\right)\ln\left(\frac{2N-1}{2N}\right)$$

Stick in any $N$ you want and you'll get your answer. Of course, this equations assume panmixie. In absence of panmixia, then it all depends upon the interconnectedness of the different populations. If some population are perfectly isolated, then a mutation will never fix in the entire species.

How much time does it typically take for a new mutation to happen and fix in an animal population?

The time to wait for the mutation to fix is typically quite negligible comparing to the time it takes for this mutation to happen. Let $\mu$ be the mutation rate. The number of mutations happening each generation is $2 N \mu$ and assuming they are neutral a fraction $\frac{1}{2N}$ of them will fix. Hence, the expected waiting time is $\frac{1}{2 N \mu \frac{1}{2N}} = \frac{1}{\mu}$. In humans, the average $\mu$ is of the order of $10^{-8}$ per site but there is a lot of variation among sequences.

So, if your mutational target is only a single site, then the expected time to fixation of a currently non-existing mutation is $10^8$ generations! If you are considering the entire genome as you mutational target is the entire genome, your mutation rate is of the order of $10$ and the expected number of generations is only $\frac{1}{10}$.

  • $\begingroup$ Perhaps just to add a source, the standard mutation rate in humans is approximately 0.5×10^−9 per basepair per year, and mitochondrial dna mutates quite a bit faster - so it depends what aspect of a human is being referenced. link Cheers $\endgroup$
    – Aaron43
    Commented Jan 19, 2018 at 18:37
  • 1
    $\begingroup$ @Aaron43 See edit $\endgroup$
    – Remi.b
    Commented Jan 19, 2018 at 19:19

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