Australia: The Land Where Time Began

A biography of the Australian continent 

WLH 50 - Migrations Versus Sources

The issue of the number of sources which contributed to the colonisation of Australia has been debated for a long time (Kirk & Thorne (eds.), 1976; O’Connell & Allen, 2004). Originally the question was framed in terms of migrations. Though the migration interpretations have continued (Reyes-Centeno et al., 2014), focus shifted from the numbers of migrations to the numbers of sources when Thorne first stated his interpretation of 2 migrations, in terms of “robust and gracile” groups, using robustness to suggest ruggedness and gracility as less rugged (Thorne, 1976, 1977). Description of H. soloensis was replaced by robustness and Negrito-like cranial anatomy was replaced by gracility, though these have become terms that are misleading and inaccurate (6) that could reflect many things besides ancestry, which include environmental adaptation (Bulbeck, 2001) and activities that are economically related (Collier, 1989). When they were defined, they were perceived as anatomical contrasts that did not come from migrations, instead reflecting 2 distinct geographical sources, they were specific (Thorne, 1984). This allowed the possibility that at varying times throughout the prehistory of Australia colonisation could have involved many migrants, in particular, arrivals from Indonesia and East Asia (China). As Thorne often put it, after migrants began arriving by sea, why not expect that they continued arriving throughout the prehistory and history of Australia? When it is accepted that the question was about sources “Robustness” and “Gracility” descriptions of cranial anatomy became the wrong contrast to apply to this comparison (contra Curnoe & Thorne, 2006a), as primitives and modern is the wrong contrast that was applied in earlier formulations. Wolpoff & Lee agree that valid contrast is in features relating to geographic origin.

The potential for models of complex population history was led to by the recognition of several different geographic sources for indigenous Australians, as there is no mechanism that could have kept populations of hunter-gatherers who arrived from different geographic sources separated or distinct. According to Pardoe (Pardoe, 2006: 14) it is not conceivable that groups with morphologies that differ widely could coexist for tens of thousands of years at the same place. Ancient mtDNA from fossil crania that were regarded as “gracile” and “robust” were analysed (Adcock et al., 2001) who found that most (7) belong to a single mtDNA clade that also includes the sequences that have been found in living indigenous Australians, which supports this notion. Different cranial morphologies were not associated with different mtDNA lines. The migrants from different regions mixed thoroughly, and the mixing evidently occurred long before the fossils were living people. In support of this interpretation the features of some specimens from the 2 large fossil samples at Kow Swamp and Coobool Creek, suggest they had some ancestry from Indonesia and some other specimens lack these Indonesian features but have other anatomies that suggest some East Asian ancestry. Different sets of features are combined in different crania and the most reasonable interpretation of this is that they had a mixed ancestry (8). According to Wolpoff (Wolpoff, 1980: 327-330), in Kow Swamp 15 the browridge is continuously developed, with only a slight dip over the nose, and the thickness of the browridge is close to the average for Solo. A sagittal keel (9) is retained in the frontal of Kow Swamp 1that continues almost to the browridge and the forehead, eliminating the groove between the browridge and the forehead. In Kow Swamp 9 the outer part of the browridge follows the temporal line backwards, forming a triangle that is backward-pointing at the upper corner of the orbit [frontal trigone]. (Wolpoff, 1980: 327-330)

Though at the same time, in the Keilor crania the resemblances are with Liujiang and Zhoukoudian Upper Cave (Thorne, 1980; Curnoe, 2007). Similarities are also shown with East Asians in other specimens such as Mungo 1 and 3, which are 2 of the earliest dated remains in Australia. Yet Mungo 1 bears close resemblances to Kow Swamp 4 and 16, while Mungo 3 (male) resembles Kow Swamp14 and 15 in frontal curvature. I.e., the range at this site encompasses most of the known fossil material from Australia (Wolpoff, 1980: 330).

Though it may be suggested by the variations in the anatomy of indigenous Australians, such as those described above, that indigenous Austrians arrived from multiple geographic sources, such as Indonesia or East Asia, it is misleading to pick through the fossils and recent specimens in order to find specific individuals with ancestry from Indonesia, East Asia or Africa, and is an invalid use of the data, because all of the skeletal samples are of mixed ancestry. Based on current evidence the migration or migrations to the Australian continent began some 50,000 BP (Hiscock, 2008; O’Connell & Allen, 2008, 2012), and by 40,000 BP humans had dispersed throughout the continent (O’Connell & Allen, 2004; Pardoe, 2006). No fossil or archaeological evidence has been found to date which would suggest that Australian populations were isolated from the remainder of the world after the beginning of migration, and there is every indication that there was significant gene flow throughout the continent (Habgood & Franklin, 2008).

Was there a Single Source Population?

A single source is the alternative to multiple sources for indigenous Australians, though the ultimate source of all human populations in the Pleistocene was Africa. The question with regard to Australia is about proximal sources. This has proven to be a more complicated discussion than for most other regions.

At the time multiple sources for indigenous Australian were being discussed the hypothesis that there need not have been more than a singles geographic source region, and that variation among indigenous Australians subsequently evolved in situ from it was put forwards by a number of workers (Abbie, 1968; Brown, 1987; Bulbeck, 2001; Cameron & Groves, 2004; Habgood, 1986; Howells, 1977; Pardoe, 1991, 2006; Pietrusewsky, 1990; Stone & Cupper, 2003; Wright, 1976). This contention is not simple to disprove, as the adaptive changes in Australia parallel changes occurring other parts of eastern Asia (Brown, 1992; Brown & Maeda, 2004), and more broadly in other parts of the Old World. The likelihood of adaptive changes occurring during the Pleistocene and Holocene is quite high, whatever the number of sources, which provides an alternative explanation for the pattern and details of variability in Australia (Pardoe, 2006) that has been difficult to disprove. There was also limited consensus on where the single source region might have been.

Whether the early Australian migrants were directly descended from an African population whose ancestors left Africa a comparatively short time ago is a possibility that can be addressed (Mellars et al., 2013; Oppenheimer, 2009). Archaeological evidence that there was a direct migration from Africa to Australia has not been found (Habgood & franklin, 2008), and to date no unambiguous evidence of a diagnostic African anatomy has been demonstrated in the fossil record of Australia. Systematic comparisons of WLH 50 to earlier African crania have failed to demonstrate unique descent from these Africans, which provides evidence for rejecting a direct African origin for indigenous Australians. However, these comparisons cannot exclude the possibility of some African ancestry for indigenous Australians.

The Simplest Origins Hypothesis

When geography and the Pleistocene pattern of ocean currents are considered, the proximate geographic origin for Aboriginal Australians the most likely possibility was in the regions that are closest to Australia – in eastern Asia and Island Southeast Asia. Indonesia was among the islands that some of the earlier scientists suggested, and an Indonesian origin, in one way or another, or what is more precise, the idea that one of the source populations for Aboriginal
Australians was Indonesian, has continued to be an important intellectual thread throughout the history of Australian prehistory. The contention is accepted as a null hypothesis by Wolpoff & Lee, that one of the ancestors of Australian Aboriginals is Ngandong or a sample that was similar to it.

The populations of Australia evolved throughout part of the Pleistocene that the continent had been occupied by humans, archaeologically, demographically and anatomically. The second hypothesis of Wolpoff & Lee is that the pattern and direction of their evolution was similar to evolution in other regions of the world; specifically that WLH 50 is different from Ngandong in ways that reflect the pattern of evolution from the Late Pleistocene in other parts of the world. This is not parallelism. It would imply there were significant archaeological and biological connections between Australia and its neighbours; therefore the continent could not be considered to be an isolated cul-de-sac.

Sources & Further reading

1. Habgood, P. J. (2016). "WLH 50: How Australia Informs the Worldwide Pattern of Pleistocene Human Evolution By Milford H. Wolpoff and Sang-Hee Lee PB - PaleoAnthropology 2014: 505−564. DOI:10.4207/PA.2014.ART88." Archaeology in Oceania 51(1): 77-79.