Pete... "... many ,if not most supposedly MYO fossils are virtually identical to the modern organism."

Simply not a fact. The only way anyone can reach that conclusion is by defining anything that seems 'different' as not related to the same modern organism. It is clear that we DO have older fossils that are both different AND related.

As to fallacies: it is true that someone **may** obtain a 'correct' answer, even though their reasoning is totally confused.

" ...it does not follow that the overall argument is wrong." It does, though. The criteria for valid, logical reasoning is not the same for evaluating data. If I tell you that mixing orange juice into concrete will produce strong concrete, and you add some and get strong concrete, it does not follow that the juice was the key.

What fallacies show is that IF we find fallacious reasoning, we should suspect the answers. If two conclusions are contradictory, at least one must be wrong....perhaps both.

By analyzing the DNA of fast breeding insects (and some other organisms), we can SEE certain mutations taking place in order to maximize odd of survival.
There was a beetle which was proven to have changed its coloration to avoid detection by predators on certain colors of tree bark..... this was a case of GENETIC mutation, not just 'lucky beetles' or some other guess. They proved this.