Phylogeography of mitochondrial DNA in Eastern Asia and America

The mtDNA diversity outside Africa is completely covered by the two macrohaplogroups M and N (with its subgroup R), both derived from the African haplogroup L3 soon after the “out of Africa” movement dated to max. 65.000 YBP [Macaulay 2005, Mellars 2006a, Mellars 2006b].

The Route to Eastern Asia

While haplogroup M individuals spread in an eastward direction only, haplogroup N tribes moved in both directions from the Arabian Peninsula. Haplogroup N is now common in Western and Eastern Eurasia, its subhaplogroups form distinct „domains", though. Only one subclade of each haplogroup is found in today’s Africa as a result of early back migrations (U6 and M1). Asia’s extant population structure is the result of a rapid movement of humans from the Near East along the Southern Asian coast. Once adapted to this habitat, people could easily spread along the Indian Ocean. The “Southern Coastal Route” (SCR) is favoured by genetic, anthropological and archeological studies.

The very similar ages (60-63 kY) of haplogroups M, N and R indicate that they were part of the same colonisation process [Macaulay 2005]. The presence of basal root haplogroups of M, N and R in all areas along the SCR – the Near East, South Asia, South East Asia and Sahul (i.e. Australia, New Guinea and Tasmania) - points out that the coastal movement was a rapid event (a “fast train”): the same founder haplotypes reached all destinations. During a delay, individual haplogroups would have developed in situ and their subclades would be found in areas populated next. It seems likely that only a part of the group remained in newly colonised areas and later spread into the Asian continent developing regionally distinct subhaplogroups, while another group of individuals moved on rapidly [Metspalu 2006].

An alternative route from the Near East to East Asia has been discussed: the Northern Asian Route (NAR) around the Himalaya barrier into Central Asia. The NAR is not supported by genetic evidence, as specific continental haplogroups with “coastal” subclades would be expected. All Central Asian haplogroups known share common ancestors with South (East) Asian haplogroups and in addition, haplogroup diversity in the South (East) is higher. Likewise, the “pincer model”, a combination of NAR and SCR, is not supported. Central Asian mtDNA phylogeny can rather be explained as a pool influenced from East and West long after the Southern Coast settlement [Yao 2004, Derenko 2007, Irwin 2010].

Entering America

America has been peopled from Eastern Asia via Beringia. This is confirmed by genetic evidence, even though a Viking landing and the possibility of an early voyage from Africa has been shown in principle. The American continent was peopled by individuals bearing subhaplogroups developed during an initial delay phase as described above [Tamm 2007]. Immigration models are discussed in [Achilli 2008]. The Native American mtDNA haplogrups have been the first four to be described and were therefore named A, B, C and D in alphabetical order [Torroni 1993]. The first two are daughter clades of the Asian haplogroups N, the latter two of haplogroup M. Extant sister clades of all four haplogroups are found in East Asia. The Native American mtDNA phylogeny has subsequently been refined and haplogroup X, another N subhaplogroup, has been identified as native to the northernmost parts of the continent [Achilli 2008]. Today, up to 15 founder lineages have been identified and comprise the pan-American haplogroups (A2, B2, C1 and D1) and several lineages with limited dispersal [Achilli 2008, Perego 2009, Perego 2010]. The spread over the American double continent is thought to have occurred very rapid and along the Pacific coast [Bodner 2012].

Much later, America’s genetic structure has been largely influenced by European colonisation, slave import [Salas 2004] and more recent immigrations for religious, political or economic reasons. EMPOP as a worldwide mtDNA population data base is continuously increasing the number of sequences included and worldwide regions covered by ongoing sampling and analyses. Currently, South East Asian and South American populations are investigated by EMPOP scientists. Sequence data are continuously incorporated into the EMPOP database and will contribute to a refinement of East Asian and American mtDNA phylogeny and a better understanding of human migrations.

Literature cited

Achilli A 2008 PLoS ONE 3:e1764
Bodner M 2012 Genome Res 22:811
Derenko M 2007 Am J Hum 81:1025
Irwin J 2010 IJLM 2010 124:195
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Mellars P 2006a Science 313:796
Mellars P 2006b Nature 439:931
Metspalu M 2006 in: Bandelt HJ Human mitochondrial DNA and the Evolution of Homo sapiens: 181
Perego UA 2009 Curr Biol 19:1
Perego UA 2010 Genome Res 20:1174
Salas A 2004 Am J Hum Gen 74:454
Tamm E 2007 PLoS ONE 2:e829
Torroni A 1993 Am J Hum Gen 53:563
Yao YG 2004 MBE 21:2265