[mnehring]

The underlying statistical model implied is invalid because it presupposes that all mutations and variations have a negative consequence.

That's pretty much the flaw I read in this story. It is the assumption that a mutation only leads to a negative trait. For example, the mutation that causes sickle cell anemia also makes it where you can't get malaria so it would be a beneficial mutation in areas where malaria is prevalent. While sickle cell anemia is harmful, it isn't even as a fraction as deadly as malaria and could result in a stronger population in malaria prone areas.

[Mount Athos]

That's pretty much the flaw I read in this story. It is the assumption that a mutation only leads to a negative trait.

The flaw is in your reading comprehension, not the study.

The author directly addresses positive mutations (natural selection). He does not pretend they do not exist as you suggest. It is brought up again in the conclusion of the study.