The mitochondrial haplogroups identified in the Paisley coprolites — A2 and B2 — are part of a classification system that organizes the diversity of human mitochondrial DNA into related groups based on shared mutations.

Mitochondrial DNA is inherited exclusively through the maternal line.

Unlike the nuclear DNA that we inherit from both parents, mitochondrial DNA is passed from mother to child without recombination — it is a direct copy, with only rare mutations accumulating over time.

This makes mitochondrial DNA a powerful tool for tracing maternal lineage over many generations.

Haplogroups are defined by specific sets of mutations that accumulated in ancestral mitochondrial genomes at specific points in human prehistory.

If two individuals share the same haplogroup, they share a common maternal ancestor at some point in the past — potentially very distant, but documentably connected through the unbroken maternal line.