[edsheppa]

...but just as likely the mutation would be snuffed out randomly...

I hope you don't mind my jumping in, but I see two problems with your argument. First, you're talking about the odds of a particular set of mutations occurring. Second, the likelihood of a particular neutral mutation occurring is different (and I'd guess generally much less) than of it's being snuffed out after it occurs.

[maro]

I don't see why that would be true. Consider the nonfunctional mutation that Nebullis is so fond of. Wouldn't you expect that the percentage of individuals in a population having this mutation (the "Empirical Percentage") would be constant, at least for relatively short periods of time after the first instance shows up? And wouldn't the probability of the mutation occurring at all be precisely the Empirical Percentage? (How could it be anything else?) (When populations come close to extinction, they go through a bottleneck, which randomly causes certain mutations to become prolific. But the a priori probability that any particular nonfunctional mutation would survive and proliferate is the same as its probability of occurring.)