Sum of the six complementary nucleotide misincorporations observed in the ancient and modern samples.

Total A+T: Total number of adenine and thymine nucleotides analysed in modern and ancient samples. Total C+G: Total number of cytosine and guanine nucleotides analysed in modern and ancient samples. The total number of nucleotide misincorporation in modern and ancient samples are obtained by the sum of the nucleotide misincorporation values found in each ancient and modern mitochondrial fragment analysed (see Tables S1 and S2, where the nucleotide misincorporation values are scaled to compensate the local nucleotide composition bias).Corrected Ancient Sample: the values of nucleotide misincorporation among ancient sequences, scaled to match the values of total modern nucleotides analysed. For example: Corrected Ancient Sample for A→G T→C complementary group was calculated as (Ancient Sample A→G T→C)*(Total A+T in Modern Sample)/(Total A+T in Ancient Sample).