The bones themselves, even when physically well-preserved in appearance, may contain little or no recoverable genetic material.

The petrous bone, with its exceptional density and internal structure, has been found in global ancient DNA research to preserve genetic material better than other skeletal elements, often when other bones yield nothing.

This discovery, which was made through comparative studies of different bone elements at the same sites, has transformed the practice of ancient DNA sampling by directing researchers to prioritize the petrous bone whenever it is available.

Even from the petrous bone, the yield of recoverable ancient DNA in tropical environments may be low.