Cold temperatures slow the chemical reactions that degrade DNA.

Dry conditions reduce the water-mediated hydrolysis that breaks apart the DNA backbone.

Alkaline conditions inhibit some degradation pathways.

Caves can provide all three of these conditions — particularly in cold, dry, alkaline environments like those of the Alaskan Arctic — making them among the better environments for DNA preservation over long time periods.

Teeth are also particularly favorable substrates for DNA preservation.

The dense, mineralized enamel that covers the outside of the crown is not the primary source of preserved DNA — the organic content of enamel is very low — but the dentine beneath it, which has a significant organic component in the form of the collagen matrix, can preserve DNA within the crystalline mineral structure in ways that protect it from some of the degradation processes that act on more exposed organic material.