Usually, to be generally accepted, hypotheses like in the OP require multiple independent lines of evidence. (E.g., for human migrations, DNA, linguistic traces, and technical artifacts could serve as independent lines.)

Publishing this article in a wide forum like PNAS is the way of asking the community at large for reactions, for or against. If it had been a more narrowly discipline-specific article, it would appear elsewhere, like Oikos or Oecologia.