July 25, 2009

The missing mtDNA link in the southern route out of Africa

In order to substantiate the southern route hypothesis of the settlement of Australia, a link between Australia and coastal populations of Asia is needed. Australian mtDNA belongs largely to the same Out-of-Africa subclades M and N, but it is not clearly a branch of a more derived clade that would allow us to pinpoint a specific Eurasian location as a place of origin.

This paper makes the case that Australian mtDNA haplogroup M42 shares two polymorphisms with a set of Indian M sequences, suggesting more recent common ancestry between these Indians and Australians than the generic "Out of Africa" M. The simplest explanation for this is that the M42 ancestors of Australians ultimately originated in India, and were thus part of the "southern route" dispersal of humans from Africa.

BMC Evolutionary Biology 2009, 9:173doi:10.1186/1471-2148-9-173

Reconstructing Indian-Australian phylogenetic link.

Satish Kumar et al.

Abstract

Background
An early dispersal of biologically and behaviorally modern humans from their African origins to Australia, by at least 45 thousand years via southern Asia has been suggested by studies based on morphology, archaeology and genetics. However, mtDNA lineages sampled so far from south Asia, eastern Asia and Australasia show non-overlapping distributions of haplogroups within pan Eurasian M and N macrohaplogroups. Likewise, support from the archaeology is still ambiguous.

Results
In our completely sequenced 966-mitochondrial genomes from 26 relic tribes of India, we have identified seven genomes, which share two synonymous polymorphisms with the M42 haplogroup, which is specific to Australian Aborigines.

Conclusions
Our results showing a shared mtDNA lineage between Indians and Australian Aborigines provides direct genetic evidence of an early colonization of Australia through south Asia, following the "southern route".

Link

5 comments:

JACK DANIELS said...

The findings may be interesting but whether the general case is proven is another matter.

In the first instance, there is a substantial human fossil record in Australia that suggests an increasing trend towards gracility over time. Further, the mitochondrial DNA of Mungo Man pre-dates all known such DNA. The age of his skeletal remains is the subject of some controversy and there are estimates of 45,000 years at the lower bound and up to 60,000 years at the upper bound. Another issue concerns the finding of the cited polymorphisms and whether it is correct to assume that there is a necessary implication that they are shared by all Aboriginal people or that the only explanation would be as the result of migration from locations further west than India.

Indeed, it would be interesting if these polymorphisms were observed in other populations along the hypothesised ex Africa route.

South Central Haplo said...

Good point. this sounds lot like Terry. Where is MT M further west and Have you heard about Jwalapuram?.

terryt said...

"there are estimates of 45,000 years at the lower bound and up to 60,000 years at the upper bound".

50,000 years at the least seems to be the latest consensus.

"Another issue concerns the finding of the cited polymorphisms and whether it is correct to assume that there is a necessary implication that they are shared by all Aboriginal people".

The M42 haplogroup is very much a minority haplogroup in Australia, so doesn't necessarily represent an early arrival at all. Could easily be a later connection. The majority of Australian mt haplogroups are N-derived.

Ponto said...

Australian Aborigines are composed of at least two major immigration events to Australia, one about 50 kya and a more recent one dating to 10 kya. Aborigines have had a long contact with their SE Asian neighbours and with the people from New Guinea. They are not quite an isolated people from 50 kya as many believe.

terryt said...

I'd agree with your two migrations assessment but I'd place your 10k one a bit earlier, perhaps even 20k or beyond. I think it has a connection with the Kow Swamp type (dated 15k-20k) and/or with the edge-ground axe (associated with Hoabinhian?). These are probably in turn connected with a further push into the Pacific Ocean, to the Northern Solomons. Further I believe that any early 'Caucasian' connection between Europeans, the Aborigines and the Ainu is easily explained. You may care to look at my reasoning in the essay:

http://humanevolutionontrial.blogspot.com/2009/06/human-evolution-on-trial-into-australia.html