Just an aside: There are quite a lot of people in research that don't consider PNAS a "proper" scientific journal. That has mainly to do with the standard peer review process not being applied to a quite a lot articles appearing there (this one is NOT case of this article - which went through the usual steps).

I also have noticed that most times that people around me refer PNAS articles is to point out gross problems. Also I've heard that PNAS is quite weary of publishing rebuttals of their own published articles. While this paragraph comes from my own (small sample) experience, the paragraph above depicts a serious, objective problem.

I don't trust PNAS.