[Nebullis]

One single point mutation may or may not lead to a selectable trait. For practical purposes, the probability of such a single point mutation is the same, regardless of whether it leads to a selectable trait or not.

Have you heard of recombination? Transposable elements?

[maro]

What you say is literally true, but irrelevant. As Edsheppa pointed out, what we are really talking about (and what we should be talking about) is the probability that a mutation exists in a population at a point in time. To begin to calculate that, we have to ask ourselves what the probability is that a mutation would occur. The second question is what the percentage is of individuals with the mutation over the next relevant time span. I contend that, assuming no natural selection, these 2 numbers are identical or just about. I think Edsheppa disagrees with the latter proposition.