Australia: The Land Where Time Began
WLH 50 ancestry - mtDNA
Current archaeological reconstructions of the peopling of Australia and lands nearby indicate there were many complex events (Balme, 2013; Bednarik, 2003, Bellwood et al., 1995; Davidson, 2010; Flood, 2006; Hiscock, 2008; O’Connell and Allen, 2004, 2012; Webb, 2006). The “huge sea-level rises that flooded much of Greater Australia, reducing it to the present day archipelago” (Hill et al., 2007: 40), was no doubt one driving factor. According to Wolpoff & Lee complexity is also indicated in mtDNA studies. The strongest signals from the post-glacial world “appear to result from the movement of indigenous, rather than introgressive, DNA lineages (op. cit.)” The region, as well as the rest of the world, was also subjected to both earlier and ongoing dispersions of populations as the population of the world increased. To evaluate these reconstructions based on current genetic activity palaeogenetics is a useful approach.
A generally Asian source for Australian and New Guinean populations is supported by mt DNA as well as Y haplotype analysis, though it does not indicate a single source population (Jinam et al., 2012; van Holst Pellekaan, 2012). Early migration to New Guinea, which was followed by a second migration form Southeast Asia (van Holst Pellekaan & Harding, 2006) prior to compacting, followed by reduced habitable areas of land as the sea level rose at the close of the ice age, is one possibility. In Australia and New Guinea some of the oldest haplotypes are shared, with others being specific to each place (Friedlander et al., 2007), which is a consequence of the most recent period of isolation by the higher sea levels. The problem is the difficulty is distinguishing the different models of migration source or sources from mtDNA alone. McEvoy and colleagues used a suite of genome-wide SNPs to argue:
The Australians and other Near Oceania samples, from New Guinea and Melanesia favours the common origin hypothesis
for the original settlement of the Pleistocene Sahul continent … followed by differentiation into subregional populations. However, we cannot formally distinguish between this and an initial separation and isolation of the proto-Sahul population in mainland Eurasia followed by multiple ancient migrations to various locations in the Sahul” (McEvoy et al., 2010), emphasis added.
There is evidence of a high level of diversity of mtDNA lineages across the region (Smith et al., 2007), and much as the reconstructions of Australian habitation have converged on the models of numerous migrations, mtDNA shows the history of the entire region to be far more complex than first thought (Hill et al., 2007; van Holst Pellekaan, 2012; Xu et al., 2012). Multiple geographic sources and several migrations are suggested by a complex genetic history.
“Collectively, these [archaeological and genetic] data suggest the cultural and genetic history of Australia is more complex than a single dispersal model such as “out-of-Africa” allows” (Smith et al., 2997: 298).
The pattern of Australian migrations in a broad regional context is reflected in the mtDNA of living Australian Aboriginal people. It has been suggested (Bellwood, 1997) that island Southeast Asia (Indonesia, East Malaysia, and the Philippines) was colonised at a similar time to that of the first Australian migrations by peoples “related to the indigenous people of Australia and New Guinea … in the mid-Holocene immigration of the ancestors of the present-day inhabitants” (Hill et al., 2007: 29). Some of the migrants to the Australasian region came in migrations that were 10-30 kyr earlier from the Asian mainland (Jinam et al., 2012).
It was shown (Reich et al., 2010) that mtDNA also addresses issues in Australian and Asian prehistory. The Denisovan mtDNA recovered from Siberian finds differs markedly from Neanderthal and recent human mtDNA. Susan Sawyer from Pääbo’s lab has shown that within the Denisovan mtDNA the mtDNA from 1 of the teeth indicates greater mtDNA variation than is known from either Neanderthal or living humans (Pennisi, 2013). mtDNA that was even older on the Denisovan clade was recovered (Meyer et al., 2014) in specimens from the 430 ka Spanish site of Sima de los Huesos (SH).
The comparisons of WLH 50 by Wolpoff & Lee with some of the earlier inhabitants of Indonesia, described above, suggests that Australia of the present is a reflection of a mix of sources, just as is done by the genetic evidence (this is a conservative interpretation of the mtDNA [Huopenen et al., 2001]). The pattern of nDNA variation is a direct reflection of the mixed ancestry.
|Author: M.H.Monroe Email: email@example.com Sources & Further reading|