It is much more difficult to imagine how both the DNA evidence and the biomarker evidence could independently produce false positives pointing to the same conclusion.

The 2020 paper was also honest about the limitations of the fecal biomarker evidence.

The authors acknowledged that the preservation of biomarkers over thousands of years is not uniform and that some specimens may have lost their biomarker signal through degradation or contamination.

They acknowledged that the distinction between human and some other omnivorous mammals in the fecal biomarker profile is not always perfectly sharp.

And they acknowledged — importantly — that the question of whether DNA had moved through the Paisley sediments from younger to older contexts remained a concern that the biomarker evidence could not entirely resolve, since the biomarkers themselves could potentially be subject to some forms of post-depositional movement.