If you don’t like the argument attack the journal? There are excellent papers in PNAS, and there is also junk – but that is true for all journals. Dismissing all PNAS papers out of hand is kind of slanderous. Each paper has to be evaluated on a case by case basis, as is true for every other journal. The trouble with PNAS is that members of the National Academy get to submit papers, either their own or their good friends, and to some extent side step the more rigorous peer review one would expect. The papers are still reviewed but the submitting member gets to choose the reviewers. It is always wise to see if one of the authors of a PNAS paper is also the submitting member. If it is, then the paper should be given much more careful scrutiny before taking it on face value.