Mitochondrial DNA signifies that just about all contemporary dogs tumble into 1 of 4 monophyletic haplogroups which can be named haplogroups A, B, C, and D. Nearly all of dogs fall in haplogroup A. The mDNA "molecular clock" implies that 22,800 YBP the primary genetic divergence (break up) occurred in haplogroup A, leading to the lineages A1b and A