Haplogroup M is a human mitochondrial DNA (mtDNA) haplogroup. An enormous haplogroup spanning all the continents, the macro-haplogroup M, like its sibling the macro-haplogroup N, is a descendant of the haplogroup L3.
All mtDNA haplogroups considered native outside of Africa are descendants of either haplogroup M or its sibling haplogroup N. Haplogroup M is relatively young, having a younger most recent common ancestor date than some subclades of haplogroup N such as haplogroup R.
Origins There is a debate concerning the geographical origins of Haplogroup M and its sibling haplogroup N. Both lineages are thought to have been the main surviving lineages involved in the out of Africa migration (or migrations) because all indigenous lineages found outside Africa belong to haplogroup M or haplogroup N. Scientists are unsure whether the mutations that define haplogroups M and N occurred in Africa before the exit from Africa or in Asia after the exit from Africa. Determining the origins of haplogroup M is further complicated by an early back-migration (from Asia to Africa) of bearers of M1.
Its date of origin in absolute terms is only known with great uncertainty, as reconstruction has yielded different (but overlapping) ranges for the age of M in South Asia and East Asia. The same authors give an estimate for t of L3 as , later (2011) narrowed to the somewhat younger . Thus, haplogroup M would have emerged around 10,000 or at most 20,000 years after L3, around or somewhat after the recent out-of-Africa migration event.
Haplogroup M1
Much discussion concerning the origins of haplogroup M has been related to its subclade haplogroup M1, which is the only variant of macro-haplogroup M found in Africa. Two possibilities were being considered as potential explanations for the presence of M1 in Africa:
M was present in the ancient population which later gave rise to both M1 in Africa, and M more generally found in Eurasia. The presence of M1 in Africa is the result of a back-migration from Asia which occurred sometime after the Out of Africa migration.
Haplogroup M23 In 2009, two independent publications reported a rare, deep-rooted subclade of haplogroup M, referred to as M23, that is present in Madagascar.
The origin of M23 is still not clearly understood, a west Eurasian origin had been suggested before. Haplogroup M23 is ancient and found throughout Madagascar. It is suggested to be an Asian component with significant African component. M23 was found only in one individual in Dubai
Asian origin hypothesis According to this theory, anatomically modern humans carrying ancestral haplogroup L3 lineages were involved in the Out of Africa migration from East Africa into Asia. Somewhere in Asia, the ancestral L3 lineages gave rise to haplogroups M and N. The ancestral L3 lineages were then lost by genetic drift as they are infrequent outside Africa. The hypothesis that Asia is the origin of macrohaplogroup M is supported by the following:
The highest frequencies worldwide of macrohaplogroup M are observed in Asia, specifically in the Indian subcontinent, China, Japan and Korea where frequencies range from 60 to 80%. The total frequency of M subclades is even higher in some populations of Siberia or the Americas, but these small populations tend to exhibit strong genetic drift effects, and often their geographical neighbors exhibit very different frequencies. Deep time depth >50,000 years of western, central, southern and eastern Indian haplogroups M2, M38, M54, M58, M33, M6, M61, M62 and the distribution of macrohaplogroup M, do not rule out the possibility of macrohaplogroup M arising in Indian population. With the exception of the African specific M1, India has several M lineages that emerged directly from the root of haplogroup M. Only two subclades of haplogroup M, M1 and M23, are found in Africa, whereas numerous subclades are found outside Africa (with some discussion possible only about sub-clade M1, concerning which see below). Specifically concerning M1 Haplogroup M1 has a restricted geographic distribution in Africa, being found mainly in North Africans and East Africa at low or moderate frequencies. If M had originated in Africa around, or before, the Out of Africa migration, it would be expected to have a more widespread distribution According to Gonzalez et al. 2007, M1 appears to have expanded relatively recently. In this study M1 had a younger coalescence age than the Asian-exclusive M lineages. The geographic distribution of M1 in Africa is predominantly North African/supra-equatorial and is largely confined to Afro-Asiatic speakers, which is inconsistent with the Sub-Saharan distribution of sub-clades of haplogroups L3 and L2 that have similar time depths. One of the basal lineages of M1 lineages has been found in Northwest Africa and in the Near East but is absent in East Africa. M1 is not restricted to Africa. It is relatively common in the Mediterranean, peaking in Iberia. M1 also enjoys a well-established presence in the Middle East, from the south of the Arabian Peninsula to Anatolia and from the Levant to Iran. In addition, M1 haplotypes have occasionally been observed in the Caucasus and the Trans Caucasus, and without any accompanying L lineages. M1 has also been detected in Central Asia, seemingly reaching as far as Tibet. The fact that the M1 sub-clade of macrohaplogroup M has a coalescence age which overlaps with that of haplogroup U6 (a Eurasian haplogroup whose presence in Africa is due to a back-migration from West Asia) and the distribution of U6 in Africa is also restricted to the same North African and Horn African populations as M1 supports the scenario that M1 and U6 were part of the same population expansion from Asia to Africa. The timing of the proposed migration of M1 and U6-carrying peoples from West Asia to Africa (between 40,000 and 45,000 ybp) is also supported by the fact that it coincides with changes in climatic conditions that reduced the desert areas of North Africa, thereby rendering the region more accessible to entry from the Levant. This climatic change also temporally overlaps with the peopling of Europe by populations bearing haplogroup U5, the European sister clade of haplogroup U6.
African origin hypothesis According to this theory, haplogroups M and N arose from L3 in an East African population ancestral to eurasians that had been isolated from other African populations before the OOA event. Members of this population were involved in the out Africa migration and may have only carried M and N lineages. With the possible exception of haplogroup M1, all other M and N clades in Africa were lost due to admixture with other African populations and genetic drift.
The African origin of Haplogroup M is supported by the following arguments and evidence. L3, the parent clade of haplogroup M, is found throughout Africa, but is rare outside Africa. According to Toomas Kivisild (2003), "the lack of L3 lineages other than M and N in India and among non-African mitochondria in general suggests that the earliest migration(s) of modern humans already carried these two mtDNA ancestors, via a departure route over the Horn of Africa." Specifically concerning at least M1a: This study provides evidence that M1, or its ancestor, had an Asiatic origin. The earliest M1 expansion into Africa occurred in northwestern instead of northeastern areas; this early spread reached the Iberian Peninsula even affecting the Basques. The majority of the M1a lineages found outside and inside Africa had a more recent eastern Africa origin. Both western and eastern M1 lineages participated in the Neolithic colonization of the Sahara. The striking parallelism between subclade ages and geographic distribution of M1 and its North African U6 counterpart strongly reinforces this scenario. Finally, a relevant fraction of M1a lineages present today in the European Continent and nearby islands possibly had a Jewish instead of the commonly proposed Amazigh maternal ascendance.
Dispersal
A number of studies have proposed that the ancestors of modern haplogroup M dispersed from Africa through the southern route across the Horn of Africa along the coastal regions of Asia onwards to New Guinea and Australia. These studies suggested that the migrations of haplogroups M and N occurred separately with haplogroup N heading northwards from East Africa to the Levant. However, the results of numerous recent studies indicate that there was only one migration out of Africa and that haplogroups M and N were part of the same migration. This is based on the analysis of a number of relict populations along the proposed beachcombing route from Africa to Australia, all of which possessed both haplogroups N and M.
A 2008 study by Abu-Amero et al., suggests that the Arabian Peninsula may have been the main route out of Africa. However, as the region lacks of autochthonous clades of haplogroups M and N the authors suggest that the area has been a more recent receptor of human migrations than an ancient demographic expansion center along the southern coastal route as proposed under the single migration Out-of-Africa scenario of the African origin hypothesis.
Distribution M is the most common mtDNA haplogroup in Asia, super-haplogroup M is distributed all over Asia, where it represents 60% of all maternal lineages.
All Andamanese belong to Haplogroup M. It peaks in the Malaysian aboriginal Negrito tribes at almost 100% but with mtDNA M21a representing Semang; 84% in Mendriq people, Batek people 48%, (almost all belong to the specific Malaysian Negrito haplogroup M21a, this subclade also found in the Orang Asli 21%, Thais 7.8% and Malay 4.6%) It also peaks very high in Japan and Tibet, where it represents on average about 70% of the maternal lineages (160/216 = 74% Tibet, 205/282 = 73% Tōkai, 231/326 = 71% Okinawa, 148/211 = 70% Japanese, 50/72 = 69% Tibet, 150/217 = 69% Hokkaidō, 24/35 = 69% Zhongdian Tibetan, 175/256 = 68% northern Kyūshū, 38/56 = 68% Qinghai Tibetan, 16/24 = 67% Diqing Tibetan, 66/100 = 66% Miyazaki, 33/51 = 65% Ainu, 214/336 = 64% Tōhoku, 75/118 = 64% Tokyo (JPT)) and is ubiquitous in India and South Korea, where it has approximately 60% frequency. Among Chinese people both inside and outside of China, haplogroup M accounts for approximately 50% of all mtDNA on average, but the frequency varies from approximately 40% in Hans from Hunan and Fujian in southern China to approximately 60% in Shenyang, Liaoning in northeastern China.
Haplogroup M accounts for approximately 20% of island negros and 40% of manila of all mtDNA in Filipinos, among whom it is represented mainly by M7c3c and E. In Vietnam, haplogroup M has been found in 37% (52/139) to 48% (20/42) of samples of Vietnamese and in 32% (54/168) of a sample of Chams from Bình Thuận Province. Haplogroup M accounts for 43% (92/214) of all mtDNA in a sample of Laotians, with its subclade M7 (M7b, M7c, and M7e) alone accounting for a full third of all haplogroup M, or 14.5% (31/214) of the total sample.
In Oceania, A 2008 study found Haplogroup M in 42% (60/144) of a pool of samples from nine language groups in the Admiralty Islands of Papua New Guinea. M has been found in 35% (17/48) of a sample of Papua New Guinea highlanders from the Bundi area and in 28% (9/32) of a sample of Aboriginal Australians from Kalumburu in northwestern Australia. In a study published in 2015, Haplogroup M was found in 21% (18/86) of a sample of Fijians, but it was not observed in a sample of 21 Rotumans.
Haplogroup M is also relatively common in Northeast Africa, occurring especially among Somalis, Libyans and Oromos at frequencies over 20%. Toward the northwest, the lineage is found at comparable frequencies among the Tuareg in Mali and Burkina Faso; particularly the M1a2 subclade (18.42%).