Mitochondrial DNA implies that nearly all modern dogs slide into 1 of 4 monophyletic haplogroups which might be named haplogroups A, B, C, and D. Nearly all dogs tumble in haplogroup A. The mDNA "molecular clock" implies that 22,800 YBP the main genetic divergence (split) happened in haplogroup A, resulting in the lineages A1b and A2. This timing i