Thesis abstract ‘The Effect of Climate on Bone Collagen Stable Nitrogen Isotope Enrichment in Modern South Australian Mammals’

05th January 2014

Tim Anson

MA, Archaeology, School of Cultural Studies, Flinders University, Adelaide, August 1997

Archaeologists have used stable nitrogen isotope ratios in bone collagen as a supplementary method of identifying dietary and climatic influences on excavated bone materials. However, baseline isotopic values for modem ecosystems are required to make inferences about the past.

Previous research has concentrated on the use of stable nitrogen isotopes as a means of differentiating between a marine and terrestrial diet in prehistoric humans. It has been observed that bone collagen values of mammals become more negative with a decreasing component of seafood in the diet (Schoeninger et al. 1983; Schoeninger and DeNiro 1984; Walker and DeNiro 1986). Thus, in general, marine mammals have more positive values than terrestrial mammals.

The principal objectives of this study were to identify, in Australia, a relationship observed on other continents whereby climatic influences affect stable isotope uptake in the bone collagen of modern mammals. It has been observed that bone collagen values become more positive with increasing aridity. This suggests a marine influence on an obviously non-marine environment. Theories explaining this irregular situation include the effects of arid zone vegetation and soil as well as arid zone mammals’ physiological adaptations to moisture restrictions.

This study independently replicated the observations of researchers on other continents, namely Africa and North America, who have identified the above mentioned anomalies.

To test this, modem mammalian bone was collected from a transect which covered a range of climatic regimes. In this case the South Australian eastern border with Victoria and New South Wales was used. The southernmost collection zone, which included the locales of Mount Gambier and Cape Northumberland, has a mean annual rainfall ranging from 700 to 800 mm. This contrasts with the more arid collection zone of Innamincka some 1200 km to the north where the mean annual rainfall ranges from 150 to 200 mm. A number of collection zones between these two extremes were also sampled in order to identify a point at which the effects of aridity begin to act on bone collagen  values.

Mammal bone collagen values collected in this study were found to comply with the Wends observed in other studies of this nature. Mean 6% values for herbivores ranged from 7.05e. 19% at Mount Garnbier on the high-rainfall southern coast, to 11.42+1.93% at Innamincka.

In South Australia, significant bone collagen enrichment does not occur until the 200-300 mm rainfall zone at approximately 325 km from the Adelaide coast. Thus, in most cases bone collagen values should differentiate marine and terrestrial components in prehistoric human diets along the South Australian coast and adjacent inland regions.

References

Schoeninger, M.J. and M.J. DeNiro 1984 Nitrogen and carbon isotopic composition of bone collagen in marine and terrestrial animals. Geochimica et Cosmochimica Acta 48:625–639.

Schoeninger, M.J., M.J. DeNiro and H. Tauber 1983 Stable nitrogen isotope ratios of bone collagen reflect marine and terrestrial components of prehistoric human diets. Science 220:1381–1383.

Walker, P.L. and M.J. DeNiro 1986 Stable nitrogen and carbon isotope ratios in bone collagen as indices of prehistoric dietary dependence on marine and terrestrial resources in southern California. American Journal of Physical Anthropology 71:51–61.

Anson, T.
Thesis abstract 'The Effect of Climate on Bone Collagen Stable Nitrogen Isotope Enrichment in Modern South Australian Mammals'
June 1998
46
52–53
Thesis Abstracts
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