When issues began surfacing around the now-retracted Nature papers from Haruko Obokata at the Riken Center for Developmental Biology on the discounted STAP method, some wondered how the papers got through the peer review process.
The news department at Science reported in June that early versions of the papers had been rejected by Cell, Science, and Nature.
The Cell reviewers raised concerns regarding methodology and the evidence needed to meet such extraordinary claims, Science noted then.
As correspondence obtained by Retraction Watch and ScienceInsider indicate, reviewers of these early versions of the papers for Science and Nature had similar misgivings.
"This is such an extraordinary claim that a very high level of proof is required to sustain it and I do not think this level has been reached," one reviewer for Science said, according to Retraction Watch. That same reviewer noted that the paper included a reconstructed image and had a "suspiciously sharp" band edge.
As ScienceInsider reports, a reviewer for Nature likewise said that the authors needed to include "a full step by step account of their method such that the community can rapidly validate the reproducibility of the findings."
While both Science and Nature rejected the paper at this point, ScienceInsider notes that Nature left open an option for resubmission if further experiments addressed their reviewers' concerns.
Just what changed between then and the publication of the now-retracted articles last January is unclear, ScienceInsider says.