By restricting sampling to the left petrous bone, the researchers created a rule: only one sample per individual, since any given person has only one left petrous bone.

From the 64 successfully analyzed samples, genome-wide data was generated — meaning that researchers had enough genetic information from across the genome to conduct a range of analyses beyond simply identifying whether the DNA was human.

They could determine biological sex, examine patterns of genetic ancestry, calculate coefficients of relatedness between individuals, assess dietary isotopes in conjunction with other lines of evidence, and compare the ancient genetic data to modern reference populations.

The sex determination from genomic data works through the sex chromosomes.