These two methods address the same question (was this coprolite produced by a human?) through entirely different biochemical routes.

Ancient DNA analysis identifies specific DNA sequences and compares them to reference databases.

Fecal lipid biomarker analysis identifies specific cholesterol metabolites and compares their ratios to reference profiles for different mammalian species.

The two methods could fail independently through entirely different error mechanisms.

When both point to the same answer, the convergence is genuinely informative.

The evidentiary architecture of the Paisley research — built progressively over twelve years of work, from the original 2008 paper through the expanded 2012 study to the 2020 biomarker paper — is an example of how a strong evidentiary case is built in practice.

Not by starting with a perfectly supported claim and defending it against all comers, but by starting with an important but imperfectly supported claim, engaging honestly with the specific weaknesses identified by critics, and finding new evidence that addresses those weaknesses through independent methods.