Not all mutations are of equal weight. Some are really trivial. Others have a noticeable effect: One gene produces major changes in stickleback fish. So just counting mutations will accomplish little. And as I said before, all that is required for speciation is that the two populations no longer breed together. That can be due to a trivial factor. I don't think your attempt to model this stuff is on the right track.
Start back in the past. How far? Take you pick, but find a spot.
Figure out how many mutations it takes to get from there to here in your chosen species.
The rest is left as an exercise for the student. (Show your work.)
I think you might be forgetting that most fatal and severely detrimental mutations will be eliminate prior to conception or prior to birth. The odds of a sperm cell conceiving are a billion to one. Egg cells have gone through fewer divisions and will have fewer mutations.
Just something to enter into your equations. Personally, I think your formulas are not very well thought out. The fact that you haven't mentioned this as a factor tells me you haven't studied the problem.
It is refressing to encounter a real argument, but I think as you study it, you will find others have been there before you.
- Fixed population of 500 individuals
- Genome size of 500 loci
- Every new gene has a relative fitness
- - 1% have 0.8
- - 10% have 0.9
- - 72% have 1.0
- - 10% have 1.1
- - 1% have 1.2
- Total relative fitness for an individual is the product of the fitness of the genes in its genome
- Pairs of individual are selected randomly for reproduction in proportion to relative fitness
- Genes at each locus are selected from one or the other parent with equal probability of 1/2
- Mutations are introduced at a rate of one in 10^6 which is at the conservative end of your range
I ran the simulation 5 times. It took an average of about 2000 generations to completely fix 10 new genes. That is 2% of the genome which seems to me a reasonable analog for the development of a new species.
I'm sure you'll disagree so I ran it three more times and waited for 25 new genes to fix. This took an average of about 6000 generations.