Revealing the prehistoric settlement of Australia by Y chromosome and mtDNA analysis

Revealing the prehistoric settlement of Australia by Y chromosome and mtDNA analysis
Georgi Hudjashova, Toomas Kivisilda,b,c, Peter A. Underhilld, Phillip Endicotte, Juan J. Sanchezf, Alice A. Lind, Peidong Sheng, Peter Oefnerh, Colin Renfrewc,i, Richard Villemsa, and Peter Forsterj, 2007.

Published and new samples of Aboriginal Australians and Melanesians were analyzed for mtDNA (n = 172) and Y variation (n = 522), and the resulting profiles were compared with the branches known so far within the global mtDNA and the Y chromosome tree. (i) All Australian lineages are confirmed to fall within the mitochondrial founder branches M and N and the Y chromosomal founders C and F, which are associated with the exodus of modern humans from Africa ≈50–70,000 years ago. The analysis reveals no evidence for any archaic maternal or paternal lineages in Australians, despite some suggestively robust features in the Australian fossil record, thus weakening the argument for continuity with any earlier Homo erectus populations in Southeast Asia. (ii) The tree of complete mtDNA sequences shows that Aboriginal Australians are most closely related to the autochthonous populations of New Guinea/Melanesia, indicating that prehistoric Australia and New Guinea were occupied initially by one and the same Palaeolithic colonization event ≈50,000 years ago, in agreement with current archaeological evidence. (iii) The deep mtDNA and Y chromosomal branching patterns between Australia and most other populations around the Indian Ocean point to a considerable isolation after the initial arrival. (iv) We detect only minor secondary gene flow into Australia, and this could have taken place before the land bridge between Australia and New Guinea was submerged ≈8,000 years ago, thus calling into question that certain significant developments in later Australian prehistory (the emergence of a backed-blade lithic industry, and the linguistic dichotomy) were externally motivated.

Conclusions
The mitochondrial and Y chromosomal results presented here point toward one early founder group settling both Australia and NG soon after the exodus from Africa ≈50–70,000 years ago, at a time when the lowered sea levels joined the two islands into one land mass, necessitating sea travel only across narrow straits such as Wallace’s Line. The deep and specific phylogenetic lineages today within this former landmass indicate a small founding population size and subsequent isolation of Australia and, to a lesser extent, of NG, from the rest of the world. These founder events and the lack of contact could underlie the divergent morphological development seen in the Australian human fossil record and could also help explain the remarkably restricted range of Pleistocene Australian lithic industries and bone artifacts compared with contemporaneous cultures elsewhere in the world (55).

Estimated dates for mtDNA:

Region Hg N ρ SE Age, yr
Aus/Mel M 50 7,9 1,1 53,400 ± 7,500
Aus/Mel Q’M29 27 6,6 1,4 44,300 ± 9,800
Aus/Mel Q 22 4,7 1,0 32,000 ± 6,500
Mel Q1 11 3,2 0,9 21,500 ± 6,100
Aus/Mel Q2 4 4,5 1,4 30,400 ± 9,300
Mel Q3 7 3,1 0,8 21,300 ± 5,500
Mel M29 5 2,8 1,2 18,900 ± 8,300
Mel M27 7 5,9 1,4 39,600 ± 9,800
Mel M28 8 3,0 1,0 20,300 ± 6,500
Mel M28a 6 1,7 0,7 11,300 ± 4,500
Aus M42 6 6,0 1,3 40,600 ± 9,000
Aus/Mel N 51 7,9 1,1 53,200 ± 7,300
Aus N12 4 2,5 1,1 16,900 ± 7,200
Aus S 12 3,8 0,8 25,400 ± 5,200
Aus S1 4 3,3 1,1 22,000 ± 7,700
Aus S2 4 2,3 0,8 15,200 ± 5,100
Aus/Mel R 33 8,6 1,2 58,400 ± 8,400
Aus/Mel P 31 7,6 0,9 51,700 ± 5,800
Mel P1 6 4,5 1,0 30,400 ± 6,500
Mel P2 7 1,9 0,6 12,600 ± 4,000
Aus/Mel P3 5 5,8 1,2 39,200 ± 8,200
Aus/Mel P4 8 9,8 1,9 65,900 ± 13,200
Aus P4b 3 7,0 1,7 47,300 ± 11,700
Mel P4a 5 3,8 1,1 25,700 ± 7,500

Y chromosomes in PNG and Aborigines.

Fig. 3.

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