The recovery of ancient DNA from archaeological remains is not guaranteed.

DNA degrades over time, affected by temperature, humidity, microbial activity, and the chemistry of the burial environment.

Tropical and subtropical climates are particularly harsh for DNA preservation — the warm, often humid conditions of southern Mexico and the Yucatán create conditions that tend to accelerate molecular degradation.

The fact that any usable ancient DNA was recovered from remains in this region at all reflects both specific preservation conditions within the chultún and the sensitivity of modern extraction methods.

The primary source for ancient DNA in this study, as in much current ancient genomics work, was the petrous bone — specifically the left petrous bone of each individual.