Ancient Poop Yields New Insights, But Questions Remain About DNA Analysis Techniques
Researchers are extracting and analyzing ancient DNA from coprolites - fossilized feces – to reveal details about the diets and gut health of past populations. A recent study published in PLoS ONE has sparked debate regarding the reliability of methods used to identify ancient organisms within these samples.
Analyzing ancient DNA is a delicate process.Labs employ high-tech clean rooms to minimize contamination and utilize next-generation sequencing optimized for the fragile nature of the genetic material. traditionally, scientists also examine the ends of DNA fragments for distinctive fraying, a characteristic of age, to verify authenticity.However, the PLoS ONE study’s methodology raises concerns. according to researcher Jessica bos, “you can’t tell easily whether these chemical modifications that occur in ancient DNA have happened” with the technique used.
The accessibility of older,less costly techniques is a key advantage,argues researcher Colleen Capone. She posits that the risk of false positives from modern DNA contamination is relatively low, given that many of the organisms targeted are unlikely to survive long outside the human gut.
While some researchers express skepticism about bacterial identifications due to the challenges of accurate identification in ancient samples, others are more confident in findings related to larger parasites like worms. Frank Hubener, who led a 2021 study analyzing coprolites from a cave, stated that the parasite findings are “believable,” given existing biological knowledge.
Bos suggests a crucial next step would be to analyze the same samples using both older and newer, more stringent DNA analysis techniques. “That would have been a really good way to move forward,” she says,to determine what the older methods reliably detect that is also confirmed by the most advanced procedures.
