Mitochondrial DNA (mtDNA) is genetic material found in mitochondria, the energy-producing structures inside cells. Unlike nuclear DNA, mtDNA is inherited almost exclusively from the mother, passing unchanged from mother to child except for rare mutations.
This makes mtDNA especially useful for tracing direct maternal ancestry over thousands of years. Because mtDNA mutates at a relatively steady rate, scientists use it to define maternal haplogroups and reconstruct ancient population movements, human origins, and evolutionary relationships across different regions and time periods worldwide.