Mitochondrial DNA indicates that almost all modern dogs fall into one of four monophyletic haplogroups which are named haplogroups A, B, C, and D. The majority of dogs fall within haplogroup A. The mDNA "molecular clock" indicates that 22,800 YBP the first genetic divergence (split) occurred in haplogroup A, resulting in the lineages A1b and A2. This timing is the oldest known between any two dog mDNA lineages. As humans migrated across Siberia, through Beringia, and down through the Americas, archaeological remains indicate that their mDNA lineages diverged several times. Based on these timings, and the timings of several dog divergences found from early dog remains across these regions, it was discovered that there was a correlation between human and dog migrations and population divergences. This correlation suggests that where people went, their dogs also went. Tracing back through these human and dog lineages and timings led to the inference that the dog was first domesticated in Siberia nearly 23,000 YBP by North Siberians.