The half-life of 521 years does allow for some million year old DNAs to be found. The original paper even noted this possibility in exceptionally good environme

The half-life of 521 years does allow for some million year old DNAs to be found. The original paper even noted this possibility in exceptionally good environments [1, section 4]: > Our results indicate that short fragments of DNA could be present for a very long time; at –5°C, the model predicts a half-life of 158 000 years for a 30 bp mtDNA fragment in bone. Even rough estimates such as this imply that sequenceable bone DNA fragments may still be present more than 1 Myr after deposition in deep frozen environments. It therefore seems reasonable to suggest that future research may identify authentic DNA that is significantly older than the current record of approximately 450–800 kyr from Greenlandic ice cores. [1] https://royalsocietypublishing.org/doi/10.1098/rspb.2012.1745 https://royalsocietypublishing.org/doi/10.1098/rspb.2012.174...