The origin of mtDNA haplogroup M has been matter of some controversy. A reader alerts me to a new paper which conclusively demonstrates its Asian origin, by sequencing 24 full mitochondrial genomes, which allowed the researchers to reconstruct its phylogeny.
Haplogroup M is found mainly in Asia, and its various subclades make up the great majority of Mongoloid and Indian lineages. It is also found in the Near East, the Caucasus, Asia Minor and Southern Europe, in addition to Egypt, and Ethiopia. A particular clade of M, named M1 is the main one found in the "western" range of its range, and it was hypothesized that its high frequency and diversity in Ethiopia may indicate an East African origin for the entire M.
However, M1 is geographically limited in Africa, while it is very widespread in Asia. If M originated in Africa, then it must have done so at a very old time, because it would have to spread throughout Asia and the New World. However, it would be difficult to explain how M crossed such a vast distance and yet failed to reach other populations of Africa except Ethiopians, Egyptians and a few others.
The new study has dated the Indian clades of M and shown them to be very old. This clinches the argument in favor of the Asian origin.
Haplogroup M is one of those mtDNA lineages which does not correspond well to present-day racial groups, as it spans Mongoloid, Indian Caucasoid and Paleoindian, as well as Ethiopid and various Caucasoid groups in lesser frequency. This paper represents significant progress in our understanding of human prehistory.
Now, let's wait to see what the origin of other "peculiar" lineages turns out to be, such as the mysterious YAP (Y-chromosome haplogroup DE) clade which is found in peoples such as Greeks, East Africans, Andamanese, Tibetans and Ainu...
BMC Evolutionary Biology 2005, 5:26 doi:10.1186/1471-2148-5-26
Phylogeny and antiquity of M macrohaplogroup inferred from complete mt DNA sequence of Indian specific lineages
Revathi Rajkumar et al.
Analysis of human complete mitochondrial DNA sequences has largely contributed to resolve phylogenies and antiquity of different lineages belonging to the majorhaplogroups L, N and M (East-Asian lineages). In the absence of whole mtDNA sequence information of M lineages reported in India that exhibits highest diversity within the sub-continent, the present study was undertaken to provide a detailed analysis of this macrohaplogroup to precisely characterize and unravel the intricate phylogeny of the lineages and to establish the antiquity of M lineages in India.
The phylogenetic tree constructed from sequencing information of twenty-four whole mtDNA genome revealed novel substitutions in the previously defined M2a and M6 lineages. The most striking feature of this phylogenetic tree is the recognition of two new lineages, M30 and M31, distinguished by transitions at 12007 and 5319, respectively. M30 comprises of M18 and identifies a potential new sub-lineage possessing substitution at 16223 and 16300. It further branches into M30a sub-lineage, defined by 15431 and 195A substitution. The age of M30 lineage was estimated at 33,042 YBP, indicating a more recent expansion time than M2 (49,686 YBP). The M31 branch encompasses the M6 lineage along with the previously defined M3 and M4 lineages. Contradictory to earlier reports, the M5 lineage does not always include a 12477 substitution, and is more appropriately defined by a transversion at 10986A. The phylogenetic tree also identifies a potential new lineage in the M* branch with HVSI sequence as 16223,16325. Substitutions in M25 were in concordance with previous reports.
This study describes five new basal mutations and recognizes two new lineages, M30 and M31 that substantially contribute to the present understanding of macrohaplogroup M. These two newly erected lineages include the previously independent lineages M18 and M6 as sub-lineages within them, respectively, suggesting that most mt DNA genomes might arise as limited offshoots of M trunk. Furthermore, this study supports the non existence of lineages such as M3 and M4 that are solely defined on the basis of fast mutating control region motifs and hence, establishes the importance of coding region markers for an accurate understanding of the phylogeny. The deep roots of M phylogeny clearly establish the antiquity of Indian lineages, especially M2, as compared to Ethiopian M1 lineage and hence, support an Asian origin of M macrohaplogroup.