Australia: The Land Where Time Began

A biography of the Australian continent 

Aboriginal Skeletal Remains – Determining the Geographical Origin of the Remains, that had not been provenanced, by Stable Carbon and Nitrogen Isotope Analysis

Stable carbon and nitrogen isotope analysis of bone collagen from prehistoric human remains recovered from various known localities in southeastern South Australia has provided isotopic signatures that distinguish different regions form each other: the coastal Coorong, the coastal mouth of the Murray River, Swanport (on the Lower Murray River) and Roonka (Upper Murray River). In order to determine the geographic origin of the Aboriginal skeletal remains curated at the South Australian Museum Pate et al. employed regional isotopic signatures. On the basis of isotopic values almost 85% of the unprovenanced sample (77/91) could be assigned to a particular zone, and a further 13% (12/01) could be assigned to areas that are intermediate between 2 geographic zones. Individuals with anomalous isotopic values in relation to the standard values derived from known geographic localities. An independent means of addressing geographic origin of skeletal remains that can supplement other methods such as metric, non-metric and analysis of DNA, is provided by isotopic analysis.

In Australia stable carbon and nitrogen isotope analyses of human and faunal bone and fossil emu eggshell have been employed in order to address use of the landscape by Aboriginal people, as well as environmental change during the Late Pleistocene and Holocene (Collier & Hobson, 1987; Pate 1995, 1998b; Grocke, 1997; Johnson et al. 1999; Roberts et al., 1999).

In South Australia, stable isotope analysis of bone collagen from modern marine and terrestrial mammals (Pate & Schoeninger, 1993; Pate et al., 1998; Pate & Noble, 2000; Anson, 1997; Grocke et al., 1997) have demonstrated that there are significant variations of isotopic values correlated with geographic locality. Variations in stable isotope values (δ¹³C) are predominantly related to relative proportions of marine vs. terrestrial foods and C₃ vs C₄ plant food included in diets, whereas variations in isotopes of nitrogen (δ¹⁵N) may relate to marine verses terrestrial dietary intake, trophic level, nutritional stress, water restriction, and changes, synchronic and diachronic, in patterns of rainfall (Ambrose, 1991; Pate, 1994; Pate et al., 1998; Schwarcz et al., 1999). Isotopes of oxygen, strontium and lead present in bones and teeth have been used to address migration and geographic origin in prehistoric populations (cf. Carlson, 1996; Ezzo et al., 1997; White et al., 1998; Montgomery et al., 2000; Müller et al., 2002).

Variability in oxygen isotope values in the bone phosphate of kangaroos in relation to different environmental zones within Australia has been addressed (Ayliffe & Chivas, 1990).

Therefore, stable isotope values will provide in some cases a record of long-term use of various environmental zones by animals and humans. A novel application of bone collagen stable carbon and nitrogen isotopes provides a means to determine information about diet in childhood, which can be used to address migration between environmental zones by the use of teeth as well as bone.

A novel application of bone collagen stable carbon and nitrogen isotopes as a means of determining geographical locality for museum skeletal collections lacking specific provenance is provided by this research. Archival information and biogeographical research on collectors are continuing to be the primary means of establishing provenance of prehistoric skeletal remains in Australia. Large numbers of Aboriginal remains that are unprovenanced continued to be present in museums and collections throughout Australia, however, and cannot be assigned to a specific locality without the aid of biological anthropology or chemical analyses. Also, an issue of great importance to repatriation programs across Australia is the returning of human remains to the correct Aboriginal community. According to Pate et al. there are many indigenous people who do not wish to bury human remains in their country if the provenance of the remains is uncertain. The importance to Aboriginal people of burying persons in their own country was discussed in a number of ethnohistoric sources (Taplin, 1879; Dawson, 1881; Meehan, 1971).

Aboriginal human remains that were held by the South Australian Museum, that are provenanced to the Adelaide region of South Australia, or simply to the state of South Australia were analysed by stable carbon and nitrogen isotope analysis to address the usability of the method in relation to determination of geographic origin.

Discussion

A reliable means of determining geographic origin of prehistoric skeletal remains, which had been unprovenanced, in southern South Australia has been provided by the bone collagen stable carbon and nitrogen isotope values. On the basis of this method human remains that are unprovenanced can be assigned to general geographic zones. For the successful application of the standard carbon and nitrogen isotope analysis in South Australia it was essential that the isotope values be known for prehistoric human populations from known geographic localities. Baseline isotopic values that are derived from marine and terrestrial mammals with known diets are useful for the determination of general differences in diet and landscape use among prehistoric populations, though they do not provide the detailed information that is necessary for repatriation studies, as there are significant differences in the ranges in the values of ¹³C and ¹⁵N for animals and humans (cf. human values in this study with faunal values obtained in other studies (Pate, 1998a, 1998b; Brodie, 2000).

According to Pate et al. the most likely explanation for the differences that are observed between fauna and human stable isotope values in similar South Australian habitats are:

1)    Metabolic differences between humans and fauna  and

2)    Restrictions of access to various marine and terrestrial foods in humans related to territory and other cultural factors.

In similar habitats in South Australia differences observed between human and animal stable isotope values are most likely to be explained by:

1)    Differences in metabolism between humans and fauna, and

2)    Restricted access to various marine and terrestrial foods in humans that are related to territoriality as well as other cultural factors.

Therefore, the variability of carbon and nitrogen isotopic values in human populations in prehistoric times is the result from a combination of environmental and cultural variables.

In the cases of the 2 individuals with the anomalous δ¹⁵N values it is most likely their diets included a lot of low trophic level foods. According to Pate et al. this is an explanation for the nitrogen isotope value being more negative in these individuals when compared to the majority of the sample (Ambrose, 1991). The individual with the δ¹³C value of -10.1‰ and δ¹⁵N value of 8.8‰ can be assigned to the Coorong region based on the carbon isotope value, which is very positive, and the individuals with values of -15.2‰ and 4.4‰ to the Murray Mouth zone due to the intermediate carbon isotope values.

The association between these broad geographic zones and the contemporary Aboriginal territorial boundaries or associations of landscape need to be determined in a case by case basis, because stable isotopic analyses will usually provide only the general regional locality for the human remains that are not provenanced.

There will be a correlation between broad geographic zones and the boundaries of Aboriginal communities in some cases, e.g. the Coorong and Murray Mouth regions in this study are associated with the research project related to the South Australian Museum Human Biology collections. The Narrinjerri Heritage Committee provided the access to the Swanport archaeological collection. Valuable comments regarding the revision of the manuscript was provided by Michael Westaway and Wolfgang Müller.

Sources & Further reading

Pate, F. D., et al. (2002). "Determination of Geographic Origin of Unprovenanced Aboriginal Skeletal Remains in South Australia Employing Stable Carbon and Nitrogen Isotope Analysis." Australian Archaeology(55): 1-7.