Interpretación de la experiencia

of human health over time, but overall do not support the conclusion that the people of eastern Qinghai suffered from the climatic deterioration in the mid to late Holocene:

• diet changed somewhat (cariogenicity and AMTL increased, wear decreased);

• burden of non-specific infections and frailty remained constant (overall tibial

periosteal reaction decreased, most lesions in both populations were healing);

• childhood growth disruptions remained steady (no LEH in either population);

• childhood anemias declined (fewer cases of CO/PH);

5 6 7 8 9 10 11 -13 -12 -11 -10 -9 -8 -7 -6 δ 15N δ13_C

Published human bone collagen stable isotope values

for Qinghai

Zongri (Cui et al., 2006) Xiahaishi (Ma et al., 2014)

Lajia (Zhang, 2006; mean, no SD reported) Buziping/Buzishan (Ma et al., 2014)

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• nutritional inadequacy or other stressors that impact growth attainment did not

change (no change in long bone length);

• fertility remained the same (no change in the juvenility index); and

• activity patterns did not change (no change in OA).

My findings regarding oral health are preliminary, as there was only a small sample of dentition from Mapai, and no dentition from Yangshan, in my study. Still, there were significant differences between Mapai and Xiaohandi in terms of oral health, mainly an increase in carious lesions and AMTL and a decline in dental attrition from the late Neolithic to the middle Bronze Age. Abscesses were absent at Mapai and rare at Xiaohandi, completing the picture of two populations with low rates of infectious and inflammatory processes in the oral cavity. This is somewhat unusual in agricultural populations (with the exception of Southeast Asian rice agriculturalists).

Both populations also had low rates of osteoarthritis in both upper and lower limbs, no observed spinal arthritis, and no significant difference in the rates of OA between the

populations. The trepanations and forearm amputation at Mapai/Yangshan, and the fractures of an ulna and a cranium at Xiaohandi, are too anecdotal to draw any population-wide conclusions, but do suggest a possible increase in conflict in the later period. This conclusion would need to be strengthened by more data from contemporaneous middle Bronze Age sites in eastern Qinghai. Periosteal new bone formation on tibiae declined by half from the earlier to the later population, and most of the cases from Mapai/Yangshan and all the cases from Xiaohandi showed healing, indicating low frailty in both populations. CO and PH also declined between populations, suggesting a decrease in childhood anemias.

The lack of LEH at both sites, and the similar stature attainment in both males and females, along with the decrease in CO and PH, suggest that rates of childhood insults was not

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high, and that they declined slightly between the populations. Since frailty does not appear to have been high in these groups (most periosteal new bone was healing at the time of death), it is unlikely that these findings are due to high frailty and high mortality, and more likely that they are due to low frequency of childhood stressors.

The lack of indicators for growth disruption, interpersonal violence, infectious disease, and nutritional stress in the populations I have described here suggest that a cautious approach is needed in the interpretation of climatic impacts on human lifeways in the past. As the biodistance data suggest, there was possibly population movement into the area after the 4000 BP climate change event, and people continued to practice agriculture in the middle Bronze Age. It is therefore dubious to interpret highly variable, gradual, and localized cultural change as evidence of widespread cultural “collapse” or drought-induced stress in the Chinese Neolithic and early Bronze Age (Dong et al., 2012; Liu and Feng, 2012), at least until the region has been

systematically surveyed to confirm that there were changes in settlement density, and more evidence has been found that social change took place under duress.

After the 4000 BP climate change event, in the second and third millennia BCE, eastern Qinghai did not see a decline in health, or a dramatic increase in conflict, according to my data. According to existing archaeological data, in the Bronze Age cultures of eastern Qinghai, including Qijia, Kayue, and Xindian, agriculture was continuously practiced as a key element of the human subsistence system. Crop diversification and spatial diversification, both forms of risk management in agropastoral production (Marston, 2011), also probably played a role in adapting to the environment of the second millennium BCE: wheat and barley were introduced, and there seems to have been some economic specialization of neighboring groups, with the people of the

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Kayue Culture specializing in pastoralism and the people of the Xindian Culture specializing in agriculture (see Chapter 6 for more on evidence of risk management strategies).

Based on the human health data presented here, between the late Neolithic people of Mapai/Yangshan, and the middle Bronze Age people of Xiaohandi, there seems to have been some small changes in health, but continuity in most measures. This accords well with

archaeological evidence for gradual change and only slight diversification of subsistence systems in Bronze Age eastern Qinghai. These slight subsistence changes were perhaps required to meet people’s needs in a more arid environment, or to deal with new cultural contacts or neighbors with differing economic strategies, but they constituted a reform and not a collapse of the existing subsistence system. They therefore constitute incremental, rather than transformational, adaptation by the people of eastern Qinghai to late Holocene climate change.

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