In human genetics, Haplogroup M is a human mitochondrial DNA (mtDNA) haplogroup.
An enormous haplogroup spanning many continents, the macro-Haplogroup M is a branch of the African haplogroup L3, and is believed to have originated in Africa some 80,000 years before present.
The two haplogroups M and N are believed to represent the initial migration by modern humans out of Africa. Haplogroup M in particular represents the dispersal of modern human into Eurasia some 60,000 years ago along the southern Asian coastline.
Among the subgroups of M are M*, M1, C, D, E, G, and Z.
Owing to its great age, haplogroup M is one of those mtDNA lineages which does not correspond well to present-day racial groups, as it spans Mongoloid, South Asian Caucasoid and Paleoindian, as well as Ethiopid and various Caucasoid groups in lesser frequency.
The M1 variant haplogroup is found in the Near East and the Caucasus, and is the only M branch to be found in sub-Saharan Africa. As such, it is believed to represent a "reverse migration" from North Africa or the Near East into sub-Saharan Africa.
Spread of haplogroup M. Image source