So the next thing you have to know is how he's connecting his mutation rates to the "2 of 6 total offspring survive". That he even mentions such a number makes me think he's structured the problem solution incorrectly. The proportion of offspring that survive should be a function of the mutation rates, not something that is specified.
Also, specifying the number of total offspring (6) is arbitrary. If only 1/3 of offspring survive then an average of 5 total offspring per couple means eventual extinction, 6 total offspring means stasis, and more than 6 means eventual overpopulation.
Look at it another way. Researchers have measured the point mutation rates of many organisms, including humans. It probably ranges from around 1 to a few hundred point mutations per reproductive event, depending upon the mutation rate for the organism and the size of its genome.
Mendel's Accountant says that using the mutation rates researchers have measured results in extinction, so what is Mendel's Accountant trying to say? I can only guess that Mendel's Accountant is saying that since we're not extinct that researchers must have mismeasured the mutation rates. My own guess is that the Mendel's Accountant program has flaws.
Are you a programmer? The program itself can be found at
Mendel's Accountant. Someone must have mentioned this program here before because I apparently downloaded it a couple years ago. It's written in Perl and is tiny, far smaller than the software for this discussion board. I doubt it has any of the sophistication they claim, particularly since it arrives at conclusions that are at odds with reality. But if you're a programmer we can look through it together and figure out if what it's doing makes any sense.
--Percy