Australia: The Land Where Time Began

A biography of the Australian continent 

Physical Anthropology 

Davidson suggests the first question is the validity of hominin fossil classifications as a framework for gaining an understanding of the past. In 2003 the discovery of strange fossil hominin remains at Liang Bua on the Indonesian island of Flores (Morwood et al., 2004), an island in the Lesser Sunda group that have always been separated from both Sunda and Sahul by sea barriers. That this was a new species was the straight forward view, Homo floresiensis (Brown et al., 2004), that is related distantly to humans, which if the present dating is confirmed, would have survived on Flores for a long time after the colonisation of Australia (Westaway et al., 2009).

Davidson describes the different interpretations of this evidence as throwing the discipline physical anthropology into an unresolved crisis. Various workers in the discipline have made claims involving comparisons of 1 or more characters with all known hominins from Australopithecus afarensis (Homo habilis, H. rudolfensis, H. georgicus, H. antecessor), or described the remains as being of modern humans with some type of pathology, or with no pathology (see Aiello, 2010). The dating of the earliest remains at Liang Bua (Westaway et al., 2007b) is earlier than most estimates modern humans that left Africa, which makes any claim that these are the remains of modern humans are problematic. The hypothesis that H. floresiensis descended from early H. erectus in Indonesia as a result of extreme insular dwarfing (Kaifu et al., 2011), which according to Davidson would forestall speculation about the earlier expansion of hominin species, which are not known of outside Africa.

It has been argued that it is made less likely modern humans passed through Flores on their way to Sahul because of the H. floresiensis being present on Flores (Balme et al., 2009). Davidson suggests it is possible modern humans colonised the Lesser Sundas when they came from the east at a later time (Davidson, 2007a). This argument is supported by the weak genetic signal of pre-agricultural populations in Bali that had coalescence ages of 8,200 BP or 12,700 BP, which is suggested to have probably involved colonisation from further east in Indonesia or from Melanesia (Karafet et al., 2005). Analysis of Denisovan genetic material in Australia, New Guinea and some of the Southeast Asian islands add further support (Reich et al., 2011).

A further problem for archaeohistory generally is the disputes about the skeletal remains from Flores. Davidson asks if the identification and naming of species, and in particular the method of identifying relationships between such species, are good enough to allow the definition of patterns of movement of hominins out of Africa. Included among the remains at Liang Bua are many skeletal parts of one individual. How much confidence can there be in the groupings, names and relationships that have been applied to other, more fragmentary fossils,  if such complete remains are so difficult to interpret?

A new species of hominin has been identified in  north east Asia at Denisova in the Altai Mountains, eastern Russia, on the basis of its ancient mtDNA (Krause et al., 2010) and its whole genomic DNA (Reich et al., 2010). The remains the genetic data was recovered from are a large upper molar and a finger bone found in mixed sediments that are not related to the sediments from other parts of the cave that have been well dated (see supplementary on-line material [SOM] in Reich et al., 2010), which means they have not been dated, though Davidson suggests they are probably less than 125,000 years old. According to Davidson such remains are not diagnostic; therefore it will not be possible to identify other Denisovan bones unless skeletal remains are found that preserves the aDNA (ancient DNA) of Denisovan type. Davidson suggests some of the skeletal remains from China that are less well-classified may actually be those of Denisovans. Also, there could be hominin species that have not yet been recognised. Anomalous skeletal remains from Mongolia, Southwest China, and Laos have recently been described (Coppens et al., 2008; Curnoe et al., 2012; Demeter et al., 2012) could be Denisovans or new species. Together with this possibility, the high proportion of Denisovan DNA that has been found among modern people of Sahul (Reich et al., 2011) has raised the possibility that Sahul was first colonised from East Asia, either through Taiwan or Luzon, or on the eastern side of the Sunda Shelf.

Interpretation difficulties of skeletal remains have always been apparent in Australia as a result of the conflict between the trihybrid (Birdsell, 1967), dihybrid (Thorne, 1977b) and single origin theories (Brown, 1997a), and the persistence of beliefs in multiregional evolution long past the time it has been rejected by the rest of the scholarly world (e.g., Groves & Lahr, 1994). According to Davidson, in Australian skeletal remains the suggestion that robustness might indicate a close genetic relationship with Homo erectus from Java has been rejected a number of times (Brown, 1992, 2010; Westaway & Groves, 2009). Davidson suggests that the determination to give names to groups of fossils as though they represented species that were as reproductively isolated as living biological species, is one of the reasons for such confusion in Australia. He suggests representing the evidence in terms of variable interbreeding populations can give clearer insights (Pardoe, 1991a).

Sources & Further reading

1. Iain Davidson in Dennell, Robin & Porr, Martin, eds., 2014, Southeast Asia, Australia, and the Search for Human Origins, Cambridge University Press.