Dense, mineralized tissues — bone and especially tooth dentine and enamel — tend to preserve DNA better than soft tissues because the mineral matrix protects the biological molecules from the physical and chemical processes of degradation.

The permafrost conditions at Yana RHS added another layer of preservation: cold temperatures slow the chemical reactions that degrade DNA.

For the Yana teeth, the combination of dense tooth tissue and permafrost preservation produced samples that, while still heavily degraded relative to modern DNA, retained enough authentic ancient sequence to reconstruct the genome with sufficient coverage for meaningful analysis.

The international team that conducted the analysis — led by Professor Eske Willerslev of the University of Cambridge and the Lundbeck Foundation Centre for GeoGenetics at the University of Copenhagen, and including first author Martin Sikora — extracted DNA from the dental material, sequenced it using next-generation methods, identified the authentic ancient signal using the damage-pattern approach, and then compared the resulting genomes to a vast comparative dataset of modern and ancient human genomes from across Eurasia and the Americas.

The comparison is where the discovery happened.