Tuesday, January 22, 2013

Stable isotope dietary analysis of the Tianyuan 1 early modern human

Yaowu Hu, Hong Shang, Haowen Tong, Olaf Nehlich, Wu Liu, Chaohong Zhao, Jincheng Yu, Changsui Wang, Erik Trinkaus, Michael P. Richards

PNAS July 7th, 2009
(link)

Abstract:

We report here on the isotopic analysis of the diet of one of the oldest modern humans found in Eurasia, the Tianyuan 1 early modern human dating to ≈40,000 calendar years ago from Tianyuan Cave (Tianyuandong) in the Zhoukoudian region of China. Carbon and nitrogen isotope analysis of the human and associated faunal remains indicate a diet high in animal protein, and the high nitrogen isotope values suggest the consumption of freshwater fish. To confirm this inference, we measured the sulfur isotope values of terrestrial and freshwater animals around the Zhoukoudian area and of the Tianyuan 1 human, which also support the interpretation of a substantial portion of the diet from freshwater fish. This analysis provides the direct evidence for the consumption of aquatic resources by early modern humans in China and has implications for early modern human subsistence and demography.

Understanding human adaptations to the environment and specifically their subsistence strategies is a key part of determining the processes and nature of human evolution. In particular, the position of the Tianyuan 1 human fossil remains as one of the oldest marine isotope stage (MIS) 3 modern humans in Eurasia (1, 2) poses the question of whether there might have been changes in human dietary spectra and emphasis associated with the spread of modern human biology. There have been suggestions, based on European faunal assemblages and inferred from technological changes associated with the emergence of the Upper Paleolithic, that there was a shift in human predatory abilities and associated changes in diet. At the same time, carbon and nitrogen stable isotope analyses of both late archaic humans (Neandertals) and Upper Paleolithic early modern humans in Europe (3, 4), as well as analyses of small animal remains (5), have suggested that there was a shift to a broader dietary spectrum around the time of, or shortly after, the spread of modern humans, probably including greater emphasis on aquatic resources. Yet, analyses of western Eurasian archeological faunal remains (6, 7), organic residues (8), and human functional anatomy (9) have suggested little change in human diet or predation before the Mid Upper Paleolithic.

In eastern Eurasia, the nature of any human dietary changes that might have been associated with the emergence of modern humans is still unclear. There is evidence for human predation on and processing of medium and large ungulates at Xujiayao, Zhoukoudian-Upper Cave and Tianyuan Cave (1012). The Zhoukoudian-Upper Cave deposits yielded the remains of freshwater carp (Cyprinus and Ctenopharygodon), plus Arca shells (10), and a bone harpoon point from Xiaogushan may be of a similar age (13, 14). There has been some discussion of human subsistence strategies in China during the Late Pleistocene based on the changes of lithic technology (15, 16). For example, Chen (15) suggested that there were at least 4 different human adaptive strategies in north China (Shuidonggou, Siyu, Upper Cave-Dongfang Plaza-Xiaonanhai, and Xiaogushan). Further away, Niah Cave in peninsular southeast Asia provides indications of changes in dietary breadth from the same age as Tianyuan Cave Layer III (17).

It is in this context that we present here carbon, nitrogen, and sulfur stable isotopic analysis of the Tianyuan 1 human remains and associated fauna from Tianyuan Cave. Stable isotope analysis has been proved to be useful for dietary reconstruction, because it provides direct evidence for human diets (18). In addition to the more commonly used carbon and nitrogen stable isotopes, sulfur isotope values have the potential to reveal if the principal foods were from terrestrial or freshwater ecosystems (1921). Therefore, sulfur isotope ratios were also analyzed to assess whether Tianyuan 1 consumed significant aquatic resources.

Discussion and Conclusion:

Carbon, nitrogen, and sulfur isotope analyses of bones from the Tianyuan 1 early modern human and the associated animals in Tianyuan Cave and the Donghulin site indicate that the human most likely obtained a substantial portion of its protein from a freshwater ecosystem, probably from freshwater fish. These data provide the earliest direct evidence of significant freshwater food exploitation by modern humans in Eurasia, even though it has been suggested (3, 4) that it may have occurred at approximately the same time period in Europe based on the relatively high δ15N values of some early Upper Paleolithic humans.

There is nonetheless increasing evidence for human exploitation of fish remains and maritime coastal resources from earlier, Middle Paleolithic/Middle Stone Age, sites in western Eurasia and Africa (3, 6, 4547). In this context, it was not the exploitation per se of aquatic resources that was unusual in the Tianyuan 1 early modern human, but the evidence for sufficient year-round freshwater fish consumption to register in its bone collagen isotopic signature. It may well be that this evidence is an additional reflection of increasing population size at this time period, additional pressure on food resources, and the associated acquisition of difficult to access small animals (terrestrial and aquatic) by human populations (cf., refs. 5 and 48). This time period is also when modern humans first appeared across most of Eurasia (1, 17, 49), a process [whatever the phylogenetic dynamics may have been (1, 50)] that must have involved substantial population increases to produce the relatively rapid dispersal of modern human biology. The stable isotopic analysis of the Tianyuan 1 may, therefore, provide insight into both MIS 3 human demography and the subsistence dynamics of early modern humans in eastern Eurasia.


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