Australia: The Land Where Time Began

A biography of the Australian continent 

Mitochondrial Control Region Sequence Variation in Australian Aboriginals

The mitochondrial D-loop hypervariable segment 1 (mtHVS1) between nucleotides 15997 and 16377 has been examined in Australian Aboriginal people from the Darling River region in New South Wales (riverine) and from Yuendumu, central Australia, which is a desert area. There were 47 unique HVS1 types were identified, which varied at 49 nucleotide positions. Statistically significant structure in the populations is revealed by Pairwise analysis by calculation of BEPPI (between population proportion index), though there are some identical HVS1 types that are present in the 2 contrasting regions. More ancient distributions may be reflected in mt HVS1 types than are reflected by linguistic diversity and other attributes that are culturally distinguishable. It is revealed by comparisons with sequences from 5 published global studies that these Australian Aboriginal people demonstrate the greatest divergence from some African people and least from highland people from PNG (Papua New Guinea), and only slightly more from some Pacific groups  (Indonesian, Asian, Samoan, and coastal PNG). It is suggested by the construction of a median network, which displays 3 main groups, that several hypervariable nucleotide sequences within the HVS1 are likely to have undergone mutation independently, which makes phylogenetic comparison with global samples difficult by conventional methods. In median networks that are constructed from Australian Aboriginal HVS1 types alone and for 1 global selection, specific nucleotide-site variants are major separators. It is suggested by the distribution of these, which require extended study, that they may be signatures of different groups of colonisers into Australia in prehistoric times, for which the time of colonisation has remained elusive.  

        The mitochondrial genome, which is valuable in the study of interspecific as well as intraspecific evolution, as a result of its mode of inheritance, which is mostly through the maternal line (Giles et al., 1980; Hausworth & Laipis, 1982,

        Absence of recombination, and rapid rate of evolution (Brown et al., 1979),

        Has been the molecule of choice in many studies of humans throughout the world (e.g. Cann & Wilson, 1983; Cann et al., 1987; Vigilant et al., 1989, 1991; Schurr et al., 1990; Di Rienzo & Wilson, 1991; Ward et al., 1991, 1993; Torroni et al., 1992, 1993a, 1993b; Lum et al., 1994; Redd et al., 1995; Soodyall et al., 1996).

An analysis of RLFPs (Cann et al., 1987) gave rise to the suggestion that all modern mitochondrial types have spread from an African source that existed about 200,000 BP. Subsequent studies have not refuted the model, and mtDNA remains in use as a powerful tool for the examination of recent population history, though it has led to contentious debate among researchers, in particular with regard to estimations of rates of mutation and interpretation of phylogenetic analytical methods. In many places such as Australia and America, where indigenous groups have been dispossessed by colonisers, in many communities social history has resulted in maternal ancestry being maintained while paternal lineages are mixed, and this is an added advantage of mtDNA studies, instead of nuclear DNA. nDNA studies have limited value in these cases, while mtDNA studies can provide information about maternal connections that are sometimes lost with the breakup of traditional groups.  

Not many Australian mtDNA studies have been published (Cann et al., 1987; Griziotis et al., 1987; Hertzberg et al., 1989; Stoneking & Wilson, 1989; Lum et al., 1994; Betty et al., 1996), none of which described diversity within the continent. As a result of this the use of published data in global comparisons contributed little information before now. Diversification within the continent has not been described by any mtDNA studies.

Australia has been inhabited by humans for at least 50,000 years (Roberts et al., 1990), and possibly very much longer. It is demonstrated by archaeological evidence that has been radiocarbon dated that Homo sapiens was present in Australia by 30,000 BP, at several sites throughout the continent that have been well documented. Tasmania is included among these sites, which has been isolated from the mainland since about 10,000 BP and is one of the extreme regions of human expansion (reviewed in Smith et al., 1993; Flood 1995, pp. 15-221).

Sources & Further reading

  1. van Holst Pellekaan, S. M., et al. (1998). "Mitochondrial Control-Region Sequence Variation in Aboriginal Australians." The American Journal of Human Genetics 62(2): 435-449

 

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27/06/2017
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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading