[Skidoo]

[ QUOTE ]
Some individual in A1 undergoes a mutation that makes them infertile with the rest of A1. They die.

This repeats endlessly until A1 is extinct.

This doesn't make any sense. If this could happen, why would it wait until the groups are separated to start occurring? Under this assumption, every species on earth should go extinct by becoming internally infertile.


[/ QUOTE ]

Yes, in exclusive terms of the process of mutation of the genome without some mechanism of repair.

As for A becoming A1, it does not matter how small the increments are. Your first bone fide instance of "speciation" in A1 is where your problem lies.

The propagation of alleles per se is not the issue, rather it is how a new group A1 can be developed from A. It's no use trying to sneak anything through using gradualism. What remains a necessity under all conditions is the continuity between parent and offspring such that the latter is reproductively compatible with (the other offspring of) the former. Otherwise, what has been produced is itself incapable of having offspring.

You are still faced with the problem of the reproductive discontinuity necessary for one mutually fertile group to develop into another.