A minimally-invasive method for sampling human petrous bones from the cranial base for ancient DNA analysis

Area of Science:

• Bioarchaeology
• Paleogenetics
• Forensic Anthropology

Background:

• Ancient DNA (aDNA) extraction often requires destructive sampling, compromising skeletal integrity for anthropological analyses.
• The petrous bone's osseous labyrinth is rich in endogenous DNA, but accessing it typically damages the skull.
• Existing methods for accessing the petrous labyrinth are incompatible with morphological studies on intact or reconstructed skulls.

Purpose of the Study:

• To introduce a novel cranial base drilling method (CBDM) for minimally invasive access to the petrous bone's osseous labyrinth.
• To evaluate the efficacy of CBDM in preserving skull structure for subsequent morphological analysis.
• To compare the aDNA yield from CBDM with established protocols and other skeletal elements.

Main Methods:

• Developed and applied a novel cranial base drilling method (CBDM) to access the osseous labyrinth.
• Compared aDNA yield (endogenous DNA, molecular copy numbers) from petrous bones processed with CBDM versus traditional methods.
• Compared aDNA yield from petrous bones to that from postcranial bones.

Main Results:

• CBDM allows access to the osseous labyrinth without significant structural damage to the cranial vault or base.
• While CBDM showed a decrease in endogenous DNA and copy numbers compared to traditional methods, it yielded more DNA than postcranial bones.
• The method enables combined craniometric and genetic analyses on the same individuals.

Conclusions:

• CBDM is a minimally invasive technique that preserves skeletal remains for complementary morphological and genetic analyses.
• This method reduces genetic data loss compared to destructive sampling of other skeletal elements.
• CBDM facilitates the study of archaeological, cultural, and evolutionary significance in human remains.