The Contamination Controls That Made the Result Credible

The ancient DNA research on the Paisley coprolites required not just the extraction and analysis of ancient DNA but the demonstration that the results were not contaminated by modern human DNA — which is present in essentially every laboratory environment where human researchers work, including the laboratories where ancient DNA analysis is conducted.

Contamination control in ancient DNA research is a significant methodological challenge that has been one of the field’s central preoccupations since the earliest work in the 1980s and 1990s.

Modern human DNA is far more abundant than ancient DNA in most laboratory environments, and if even a tiny amount of modern human DNA is introduced into an ancient sample — through skin contact, breathing, or other routes — it can overwhelm the signal from the genuine ancient sequences and produce a completely misleading result.