A Neolithic settlement where humans engaged in reaping, herding and other activities

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Bones, the most common type of remains found in excavations, are important for archaeological research. The use of modern science and technology to study bones has spawned many research fields, such as human skeleton archaeology, animal archaeology and ancient DNA analysis. Another such field is dietary analysis, which offers an essential method for determining what foods ancient humans and animals consumed.

 

Theory of dietary analysis
Research has shown that the chemical composition of animal tissues and organs reflects what is in their diets. By detecting the stable isotopic ratio of related tissue elements, such as bone collagen, it is possible to reconstruct the dietary structure of humans and animals within a long period of time. This is the theory of dietary analysis.

Currently, carbon and nitrogen stable isotopic analysis is the predominant research approach in dietary analysis. Carbon stable isotopic analysis can tell the rough ratio of C4 plants, such as foxtail millet and broomcorn millet, and C3 plants like rice, wheat and barley by determining a bone’s delta 13C value, which is the ratio of stable carbon isotopes present in the bone. Nitrogen isotopes are used to estimate trophic levels of humans and animals as well as the consumption of animal protein like meat and dairy products by measuring delta 15N, the ratio of stable nitrogen isotopes in bone collagen. Hence, study of carbon and nitrogen stable isotope ratios can reveal food structure of humans and animals in ancient China, thereby shedding light on human subsistence agriculture and animal husbandry at the time.

Dietary analysis originated in the Western archaeological community in the 1960s and 1970s. In 1984, renowned Chinese archaeologists Cai Lianzhen and Qiu Shihua introduced its theory and advocated using the method in Chinese archaeology after researching a number of sites. Since the dawn of the 21st century, advances in archaeometry and improving experimental conditions have led to substantial progress in the field of dietary analysis, elucidating human subsistence, origin of livestock and feeding practices.

 

Millets as staple food
Diet is the primary issue in human existence and social development. Thanks to archaeobotany, we can systematically and scientifically understand what ancient people ate. Studies reveal that North China had begun to cultivate foxtail millet and broomcorn millet in the mid-Neolithic period, about 9,000 years ago, marking the start of the transition from relying on fishing, hunting and gathering. Thereafter, foxtail millet became the predominant food crop in the Yellow River Valley and regions to the north.

However, archaeobotanists have largely focused on remains that were objects discarded intentionally or unintentionally, and then altered and gathered by taphonomists. Such remains are not sufficient to objectively represent food source consumption. Nonetheless, based on the theory of dietary analysis, archaeobotanical methods can be used to analyze the consumption ratio of individuals to certain categories of food, providing new scientific indicators and research perspectives for evaluating the impact of grain production on individual diet and community subsistence.

Dietary analysis of sites in North China indicates that foxtail millet and broomcorn millet were major food sources for people in the Yanshan-Liaoning area, Guanzhong region and the northern part of the country, since the delta 13C value of human bones unearthed in many sites is apparently higher than that of herbivores that ate wild plants.

After the mid-Yangshao period, about 6,000 years ago, the delta 13C value of skeletons in the Yellow River Valley rose sharply, suggesting millet had become a staple. This means that millet-based agricultural production had gradually begun to flourish and became the mainstay of subsistence agriculture in the Yellow River Valley. Interestingly, the thriving of millet-based agricultural production coincided with the vigorous expansion of the Miaodigou Culture (c.3000-c.2000 BCE).

With the transmission of the Miaodigou Culture, the mode of millet-based agricultural production was spread to surrounding regions of core agriculture areas like the east of the Gansu-Qinghai region and the Hetao region in the upper reaches of the Yellow River, becoming the principal means of livelihood for multiple groups of people.

 

Rise of wheat crops, animal husbandry
In the context of food globalization in the Old World around 5,000 years ago, wheat, barley, cattle and sheep were gradually introduced from West Asia to the east of Eurasia and to the Yellow River Valley around 4,500 to 4,000 years ago. Afterward, the cultivation of cereal crops as well as the herding of cattle and sheep were gradually accepted by agricultural populations in North China.

It is worth noting that dietary analysis of people from the Erlitou Culture (c.1900-c.1500 BCE) in the Yellow River Valley to the Western Han Dynasty (202-8 BCE) shows that millet-based production remained the main form of subsistence agriculture among populations in the north of China, while cereal agriculture and the herding of cattle and sheep made small contributions to the food structure of our ancestors.

Judging from the results of previous dietary analysis, the massive cultivation and consumption of wheat in arid northern farming areas might have started from the late Eastern Han Dynasty (25-220) to the Sui and Tang dynasties (581-907).

Outside the core agricultural areas, different types of development were displayed. For example, dietary analysis of the Gansu-Qinghai area reveals that human food structure changed dramatically about 3,500 years ago, as evidenced by the fall of the delta 13C value and the rise of delta 15N, which might be attributed to the development of animal husbandry featuring cattle and sheep stocking, or the increasing acreage of wheat and barley cultivation.

 

Various factors count
Diachronic changes of human carbon and nitrogen stable isotope data are crucial to examining the evolution of food structure and human subsistence. Varying individual diets can reflect the complexity of food structure within communities, thus providing references for studying the relations of gender and age, social stratification, division of labor and means of livelihood to the occupation of food resources.

Studies of the dietary structure of early humans, such as in the Xipo Cemetery in Lingbao of Henan Province, which dates back 5,000 years ago, and the Qianzhangda Cemetery in Tengzhou of Shandong Province, which dates back more than 3,000 years ago, show that people in the higher social stratum in some agricultural communities consumed more meat than ordinary people.

Recent studies have found the consumption of food resources in the Eastern Zhou Dynasty (770-256) differed greatly between men and women. While men ate more meat, foxtail millet and broomcorn millet, women consumed more wheat crops that were less popular at the time.
New research demonstrates that the individualization of diets in some communities had revelations to the study of cultural exchange and human migration.

For instance, dietary analysis of human bones excavated in such sites as Wadian, Meishan, Pingliangtai and Erlitou, in the Central Plains dated back 4,200 to 3,500 years ago suggests that the delta 13C and delta 15N values of certain skeletons are obviously distinct from the majority of humans in the sites. The phenomenon might be concerned with the close cultural exchange between the millet agricultural area in the north and the rice production area in the south. Similar phenomena are common in many sites in northern Shaanxi Province and the Gansu-Qinghai area dated to 4,000 years ago.

As the globalization in the Bronze Age in the Old World led to mass human migration and frequent cultural interaction, exerting strong impacts on the East Asian society, the aforementioned phenomena in northern Shaanxi Province and the Gansu-Qinghai area might have something to do with the historical background.

 

Chen Xianglong is from the Institute of Archaeology at the Chinese Academy of Social Sciences.

(edited by CHEN MIRONG)