Abstract
Prior to the introduction of wheat and barley from Central Asia during the Neolithic period, northern Chinese agricultural groups subsisted heavily on millet. Despite being the focus of many decades of intensive interest and research, the exact route(s), date(s), and mechanisms of the spread and adoption of wheat and barley into the existing well-established millet-based diet in northern China are still debated. As the majority of the important introduced crops are C3 plants, while the indigenous millet is C4, archaeologists can effectively identify the consumption of any introduced crops using stable carbon isotope analysis. Here we examine published stable isotope and dental caries data of human skeletal remains from 77 archaeological sites across northern and northwestern China. These sites date between 9000 to 1750 BP, encompassing the period from the beginning of agriculture to wheat’s emergence as a staple crop in northern China. The aim of this study is to evaluate the implications of the spread and adoption of these crops in ancient China. Detailed analysis of human bone collagen δ13C values reveals an almost concurrent shift from a C4-based to a mixed C3/ C4– based subsistence economy across all regions at around 4500–4000 BP. This coincided with a global climatic event, Holocene Event 3 at 4200 BP, suggesting that the sudden change in subsistence economy across northern and northwestern China was likely related to climate change. Moreover, the substantially increased prevalence of dental caries from pre–to post–4000 BP indicates an increase in the consumption of cariogenic cereals during the later period. The results from this study have significant implications for understanding how the adoption of a staple crop can be indicative of large-scale environmental and socio-political changes in a region.
Highlights
Beginning in the Neolithic period, China has traditionally been divided by an invisible “crop line.” The phrase “south rice north millet” 南稻北粟 has often been used to describe the phenomenon whereby communities north of the Qin Mountains and Huaihe River were known to subsist on a millet-based diet, while those located south of these landmarks subsisted primarily on a rice-based diet [1, 2]
Considering exclusive C4 consumers can have δ13C values between –13.1‰ and –3.7 ‰, and exclusive C3 feeders between –28.1‰ and –14.7 ‰ [131,132,133], our data demonstrate a marked increase in the proportion of C4 foodstuffs consumed across northern China through 9000 to 4000 BP
As the interquartile ranges (IQR) ranges and medians of the prevalence of dental caries in these three regions all fall within the range presented by other studies for agricultural societies (2.1% - 26.9%) [11, 154], we propose that this substantial increase in the occurrence of dental caries was a result of an increasing reliance on carbohydrates as a food source
Summary
Beginning in the Neolithic period, China has traditionally been divided by an invisible “crop line.” The phrase “south rice north millet” 南稻北粟 has often been used to describe the phenomenon whereby communities north of the Qin Mountains and Huaihe River were known to subsist on a millet-based diet, while those located south of these landmarks subsisted primarily on a rice-based diet [1, 2]. The phrase “south rice north millet” 南稻北粟 has often been used to describe the phenomenon whereby communities north of the Qin Mountains and Huaihe River were known to subsist on a millet-based diet, while those located south of these landmarks subsisted primarily on a rice-based diet [1, 2]. This division of agro-cultural zones was shaped first and foremost by the different climatic and geographic conditions of northern and southern China, as well as a combination of contact histories and differing socio-cultural factors [1, 3]. Stable carbon isotope analysis of human tissues can be an incredibly powerful tool to directly identify, as well as quantify, the amount of C3– (e.g. wheat, barley, rice) versus C4– (e.g. millet) based food in these different groups’ diets [4,5,6,7]
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