Australia: The Land Where Time Began

A biography of the Australian continent 

Australian-Indian Phylogenetic Link Reconstruction

Studies based on morphology, archaeology and genetics have suggested that there was an early dispersal of behaviourally and biologically modern humans from their place of origin in Africa that occurred by at least 45 Ka by way of southern Asia. Non-overlapping distributions of haplogroups within pan Eurasian M and N macrohaplogroups are shown by mtDNA lineages that have been sampled so far from South Asia, eastern Asia and Australasia. Also, support from archaeology remains ambiguous.

In the study carried out by Kumar et al. involving the complete sequencing of 966 mitochondrial genomes from 26 relic tribes in India 7 genomes have been identified which share 2 synonymous polymorphisms with the M42 haplogroups which is specific to Australian Aboriginal People.

Direct genetic evidence of an early colonisation of Australia through south Asia which followed the “southern route” has therefore been provided by the results of this study which show a shared mtDNA lineage between Indians and Australian Aboriginal People.

Most of the DNA and archaeological evidence agree with the proposition that a small group, maybe as little as 150-200 people, left Africa to colonise what is now the occupied world. There has been, however, disagreement over which route(s) they took and the time at which this spread of anatomically modern humans from Africa occurred. It is suggested by recent genetic studies, especially those that were based on mtDNA that a single “southern Route” of dispersal of modern humans extended from the Horn of Africa [northeast Africa] into Arabia and southern Asia across the mouth of the Red Sea at some time before 50 Ka (Forster & Matsumura, 2005; Kivisild et al., 2006; Mellars, 2006; Metspalu et al., 2004; Oppenheimer, 2003; Quintana-Murci et al., 2004; Torroni et al., 2006). Modern human populations colonised Australia by at least 45 ka, which according to Kumar et al. is best represented by the anatomically modern skull at Lake Mungo 3 in New South Wales (Foster & Matsumura, 2005, Bowler et al., 2003; Field & Lahr, 2006; Macaulay et al., 2005; Mulvaney & Kamminga, 1999; O’Connell & Allen, 2004;  Stringer, 2000; Stringer, 2002; Sun & Kong, 2006; Thangaraj et al., 2006), after having rapidly expanding along the coastlines of southern Asia, southeast Asia and Indonesia. Observations based on morphology have also suggested an early phylogenetic link between Indians and Australian Aboriginal People (Huxley, 2006). The documentation of individual steps in the process of colonisation based on genetics and archaeological evidence has been the major challenge to this scenario. A non-overlapping distribution of haplogroups within macrohaplogroups M and N and its subclade R (Macaulay et al., 2005) has been shown by mtDNA lineages that have been sampled to date from south Asia, eastern Asia and Australasia. At the moment the archaeological maps for both Arabia and India are mostly blank for the critical period from about 50 to about 60 ka (James & Petraglia, 2005; Petraglia & Alshararekh, 2003). Wherever there are hints of early human occupation that are available from the Patne site in western India, (Sali, 1989) Jwalapuram, southern India and Batadombalena in Sri Lanka (Deraniagala, Kennedy, 1989) they suggest closer affinities to Middle Stone Age traditions in Africa, (Mellars, 2006; Petraglia et al, 2007), while in the east of the Indian subcontinent, especially the areas of Australia and New Guinea that have been well explored, similarly “advanced” technologies in the area to the east of the Indian subcontinent have not been found (Mellars, 2006; Bowler et al., 2003; Mulvaney & Kamminga, 1999).

Results, Discussion

The Australians and New Guineans are indicated by the complete mtDNA sequencing to belong to the out-of-Africa founder types M and N, and therefore are descendants of the same African emigrants at about 50-about 70 ka as all other Eurasians (Hudjashov et al., 2007). In the context of the Eurasian phylogeny (Ingman et al., 20002; Ingman & Gyllensten, 2003; Thangaraj, 2005; Kong et al., 2003; Palanichamy et al., 2004; Kong et al., 2006; Kivisild et al., 2002; Tanaka et al., 2004; Kivisild et al., 2003; Hurles et al., 2005; Forster, 2004), however, shared branches that are more recent than the founding types M, N and R have not been reported so far, with the exception of a shared variant at nucleotide position 8793 between haplogroup M42, which is Australian specific, and haplogroup M10, which is specific for East/Southeast Asians (Hudjashov et al., 2007).

The complete mtDNA sequencing carried out by Kumar et al. of 966 individuals from 26 populations of central Dravidian and Austro-Asiatic tribes who they found shared 2 basal synonymous mtDNA polymorphisms G8251A and A9156T with the M42 haplogroup, which is specific to Australian Aboriginal People. Kumar et al. say the phylogenetic reconstruction of 7 Indian, in this study, and 6 Australian Aboriginal mtDNA sequences from a previously published source (Kivisild et al., 2006; Ingman et al, 2000; van Holst Pellekaan et al., 2006) was found to differ from previous reports (Hudjashov et al., 2007; van Holst Pellekaan et al., 2006) in the placement of G8251A polymorphism. Together with A9256T this polymorphism is present in all of the 7 Indian samples used in this study, as well as 1 previously reported Indian sample (i.e. PU202) that was based on RFLP (Passarino et al., 1996; Quintana-Murci et al., 1999; Barnabas, Shouche & Suresh, 2005) and in 4 out of 6 Australian sequences that were used in this reconstruction. The lack of G8251A in a sublineage of Australian Aboriginal People consisting of 2 genomes is an indication of a back mutation event, though G8251A and A9156T are both considered to be ancestral to M42. The present phylogenetic reconstruction of the haplogroup M42 seems, according to Kumar et al., to be parsimonious and more stable than the previously suggested M10 and M42 link through 8793 polymorphism (Hudjashov et al., 2007), being based on the combination of 2 synonymous polymorphisms and the replication of a number of samples from India, 7 in this study and 1 previously reported (Passarino et al., 1996).

It is estimated that the coalescence time of the average sequence divergence of 55.2 ± 10.8 ka of the Indian and Australian M42 coding-region sequences from the root is consistent with the first evidence of the occupation by humans is provided by 11 silcrete flakes with platforms that are plain and relatively thick that were recovered from beneath the lowest gravels in the barrier sands of the Mungo B trench, (Shawcross, 1998) which is bracketed by ages of 50.1 ± 2.4 ka and 45.7 ± 2.3 ka (Bowler et al., 2003). There is also apparent agreement with the similar or slightly earlier ages for the initial arrival of humans in northern and western Australia (Roberts, Jones & Smith, 1990; Roberts et al., 1994; Turney et al., 2001). It appears that at Mungo B trench the underlying deposits, which have been dated to 52.4 ± 3.1 ka, are culturally sterile (Bowler et al., 2003) which suggests that the colonisation of continental Australia took place from south Asia at some time after 50 ka.

Direct genetic evidence of the shared lineage provides evidence of the ancient link between India and Australia the has been long suggested (Huxley, 1870; Redd & Stoneking, 1999; Redd, 2002). Though the deep divergence (55.2 ± 10.8 ka) of the branches from India and Australia within M42, together with the evidence of the earliest population expansion, which was also the most pronounced, outside Africa in Southern Asia, which has been estimated to have occurred at about 52 ka by use of Bayesian Skyline analysis (Atkinson, Gray & Drummond, 2008), followed by high mtDNA diversity in Indian populations (Kivisild et al., 2006; Metspalu et al., 2004; Macaulay et al., 2005; Sun et al., 2006; Thangaraj et al., 2005; Kivisild et al., 2004).

It is strongly suggested, however, that Australia, and possibly as well as East/Southeast Eurasia and Papua New Guinea (Hudjashov et al., 2007), was possibly populated from southern Asia, plausibly slightly prior to or in the beginning of the expansion of population that resulted in a large number of mtDNA lineages within macrohaplogroups ‘M’ in India.

Conclusion

The results of this study have shown there is a shared mtDNA linkage between Indians and Australian Aboriginal People, and this provides direct genetic evidence that modern humans populated Australia after passing through south Asia following the “Southern Route” on their way from Africa. An early colonisation of Australia, at about 60 to 50 ka, which is quite in agreement with the archaeological evidence, is suggested by the divergence of the Indian and Australian M42 coding region sequences.

Sources & Further reading

1. Kumar, S., R. Ravuri, P. Koneru, B. Urade, B. Sarkar, A. Chandrasekhar and V. Rao (2009). "Reconstructing Indian-Australian phylogenetic link." BMC Evolutionary Biology 9(1): 1-5.