Chengbang An

East Asian summer monsoon precipitation variability since the last deglaciation

The lack of a precisely-dated, unequivocal climate proxy from northern China, where precipitation variability is traditionally considered as an East Asian summer monsoon (EASM) indicator, impedes our understanding of the behaviour and dynamics of the EASM. Here we present a well-dated, pollen-based, ~20-yr-resolution quantitative precipitation reconstruction (derived using a transfer function) from an alpine lake in North China, which provides for the first time a direct record of EASM evolution since 14.7 ka (ka = thousands of years before present, where the “present” is defined as the year AD 1950). Our record reveals a gradually intensifying monsoon from 14.7–7.0 ka, a maximum monsoon (30% higher precipitation than present) from ~7.8–5.3 ka, and a rapid decline since ~3.3 ka. These insolation-driven EASM trends were punctuated by two millennial-scale weakening events which occurred synchronously to the cold Younger Dryas and at ~9.5–8.5 ka, and by two centennial-scale intervals of enhanced (weakened) monsoon during the Medieval Warm Period (Little Ice Age). Our precipitation reconstruction, consistent with temperature changes but quite different from the prevailing view of EASM evolution, points to strong internal feedback processes driving the EASM, and may aid our understanding of future monsoon behaviour under ongoing anthropogenic climate change.

Agriculture facilitated permanent human occupation of the Tibetan Plateau after 3600 B.P.

Colonizing the roof of the world Humans only settled permanently on the Tibetan plateau about 3600 years ago. Chen et al. examined archaeological crop remains unearthed in northeastern Tibet, which elucidate the timing of agricultural settlement. Although much earlier traces of humans in Tibet have been dated to 20,000 years ago, year-round presence at the highest altitudes appears to have been impossible until the advent of suitable crops, such as barley. Surprisingly, these prehistoric farming communities expanded onto the plateau at the same time as climate was cooling. Science, this issue p. 248 Archaeobotanical data sets from the Tibetan Plateau reveal the Holocene prehistory of high-altitude human settlement. Our understanding of when and how humans adapted to living on the Tibetan Plateau at altitudes above 2000 to 3000 meters has been constrained by a paucity of archaeological data. Here we report data sets from the northeastern Tibetan Plateau indicating that the first villages were established only by 5200 calendar years before the present (cal yr B.P.). Using these data, we tested the hypothesis that a novel agropastoral economy facilitated year-round living at higher altitudes since 3600 cal yr B.P. This successful subsistence strategy facilitated the adaptation of farmers-herders to the challenges of global temperature decline during the late Holocene.

The development of agriculture and its impact on cultural expansion during the late Neolithic in the Western Loess Plateau, China:

Based on radiocarbon dating and our analysis of plant and animal remains from Buziping, a Majiayao (5300–4300 BP) and Qijia (4200–3800 BP) period site located in Dingxi, Gansu Province, China, and our review of archaeobotanical studies in the Western Loess Plateau and adjacent areas, we discuss subsistence strategies during the Majiayao and Qijia periods. We also discuss the development of agriculture in the Western Loess Plateau and its influence on cultural expansion during the late Neolithic period. Humans settled at Buziping for the first time during the Majiayao period (4890–4710 cal. yr BP by 14C dating). Charred seeds from the site indicate that people engaged in millet-based agricultural production. People continued this type of agriculture during a second phase of occupation (4130–3880 cal. yr BP by 14C dating) during the Qijia period, but the proportion of foxtail millet to broomcorn millet increased from the Majiayao to Qijia period. Raising domestic animals was another aspect of subsistence during the Qijia period. The main domestic animals were likely pigs and dogs, although hunting of wild animals also took place. Subsistence at Buziping site was affected by the rapid development of intensive agriculture that diffused across eastern Gansu Province during the late Neolithic. Our work suggests that millet-based agriculture spread from east to west across the Western Loess Plateau and likely promoted the expansions of those two cultures in the area during the Majiayao period and early–mid Qijia period. Climate change might have also promoted Majiayao and Qijia expansions and probably facilitated the adoption of rain-fed agriculture in this region.

An evaluation of competing hypotheses for the early adoption of wheat in East Asia

Abstract Recent emphasis on the recovery of plant remains from archaeological sites in East Asia permits an analysis of prehistoric cultural contact between East and West. Here we evaluate three prominent hypotheses for the introduction of wheat, a Near Eastern domesticate, to East Asia, specifically northern China. Existing evidence points to a nearly synchronous appearance of the plant, from the Inner Asian Mountains to the Yellow Sea, c. 4600–4200 years ago. Archaeological data, including the spatial distribution of directly dated wheat grains, argue against a wave of wheat-farming colonists, but point to the gradual in situ adoption of novel exotics by a diverse array of pre-existing agricultural peoples. Logic borrowed from the diffusion of innovations literature accounts for the near synchronous appearance of wheat over an enormous area, and allows for the occasional observation of anomalously older evidence without having to imagine such evidence as the origin of the diffusion.

How prehistoric humans use plant resources to adapt to environmental change: A case study in the western Chinese Loess Plateau during Qijia Period:

Fossilized charcoals can document how prehistoric humans used wood resources. Here, we present a quantitative result of charcoal fossil records, compiled with archaeobotanical data of Qijia Culture (4.3–3.8 cal. kyr BP) in the western Chinese Loess Plateau, to study how prehistoric people used plant resources and adapted to their environment. The charcoal records showed that Quercus, Ulmus, Pyrus, Acer, Picea, Prunus, and Bambusoideae were abundant during the Qijia Period, implying a warmer and wetter environment at that time. It also clearly showed that Qijia people had a strong preference to select woods in their daily life. Quercus was the most favorable wood, and thus, it was found in all samples. Many fruit trees planted in the Chinese Loess Plateau today were found in charcoal records. These fruit trees were, during the Qijia Period, at least in the process of being domesticated. Qijia people expanded the scope of using plant resources, and many new crops appeared during that time. These results provide a new insight into economic management and human adaption strategies in the Neolithic Age.

Stable Isotopic Detection of Manual Intervention Among the Faunal Assemblage from a Majiayao Site in NW China

Faunal remains from Shannashuzha in Minxian County, Gansu Province, China were isotopically analyzed to understand animal husbandry, and thus human subsistence strategy, during the Majiayao culture (5200-4800 cal yr BP) period. Stable carbon isotopic results reveal that only two pig samples clearly show a C-4-dominated diet with a mean delta C-13 value of -8.5%, which possibly indicated controlled feeding practices by human beings. No other significant manual intervention can be observed among the remaining samples, suggesting that both wild and domesticated meat sources were used at Shannashuzha. Statistically, Bos are indistinguishable from Cervidae based solely on isotopic results, suggesting that Bos may have remained in wild form during the Majiayao culture period. The presence of hare/rabbit, bamboo rat, and badger reflects the diversified food exploitation behavior.

Population history and its relationship with climate change on the Chinese Loess Plateau during the past 10,000 years

Based on compilation of a large number of archaeological and palaeosol 14C-ages, the Summed Probability Method is used to reconstruct population history and climatic patterns on the Chinese Loess Plateau during the period 8.5–3.5 cal. ka BP. During this period, the population experienced two major expansion periods and several climatic fluctuations. The first population expansion began at around 7.8 cal. ka BP, and the second at around 5.8 cal. ka BP. During the first period, although already in combination with cultivation of broomcorn millet the population growth was supported mainly by hunting and gathering. With the switch from broomcorn millet to foxtail millet, plant cultivation became the major factor promoting a second population increase. In this paper, we demonstrate that, initially, suitable climate and agriculture both can facilitate population growth and climate events had a significant influence on demographic fluctuations. However, when reaching the threshold of land capacity, population became increasingly more sensitive towards climate fluctuations.

Woodland vegetation composition and prehistoric human fuel collection strategy at the Shannashuzha site, Gansu Province, northwest China, during the middle Holocene

Charcoal analysis is a useful tool to gather information about the diversity of vegetation as well as human behaviour towards the environment and the diversified management of natural plant resources. Here we present the taxonomic identification of charcoal and calculate the percentage of each diameter class of the pieces excavated from the Shannashuzha archaeological site, Gansu Province. We discuss the implications of the data for the composition of the past woodland vegetation and prehistoric human fuel collection strategy. Twenty-two taxa were identified from 2,241 charcoal fragments with a further 50 fragments unidentified. Picea, Pinus, Bambusoideae, Salix, Populus, Quercus and Betula were abundant in many samples, although Bambusoideae is probably over-represented due to its high chance of being preserved. The vegetation around the Shannashuzha site had a typical mountain character and the main vegetation types reflected by the charcoal records included conifer woods, mixed broadleaved/conifer woods and riverbank broadleaved woods. This vegetation is similar to the modern vegetation and therefore the climate at that time is deemed to have been similar to or slightly warmer than today. Abundance was probably an important factor in the fuel collection strategy of the people. Collection of wood with a small diameter was a purposeful choice by prehistoric people, probably because it was less time-consuming in the study area, which was rich in wood resources. We conclude that in this region, prehistoric people selected firewood depending not on its type, but rather on its size (diameter). Charcoal from fruit trees found at this site and at many others nearby indicates that there was a common and long history of fruit utilization by prehistoric people in the western Loess Plateau. These results provide valuable information and a new insight into the interaction between human activities and plant resources in the Neolithic period.

Human diet and subsistence strategies from the Late Bronze Age to historic times at Goukou, Xinjiang, NW China:

Human diet and subsistence strategies from the Late Bronze Age to historic times (1600 BC–AD 900) are explored for the Goukou site, Xinjiang, using human and other animal stable isotope analyses alongside radiocarbon dating and preliminary archaeobotanical studies. Our results show that during the Late Bronze Age, human bones have mean δ13C and δ15N values of −14‰ and 12.9‰, respectively; during the Early Iron Age, they have mean δ13C and δ15N values of −16.4‰ and 10.1‰, respectively; from the time of the Warring States to the Han Dynasty, the mean δ13C and δ15N values are −14.8‰ and 12.2‰, respectively; and from the Jin–Tang Dynasties, human bones have mean δ13C and δ15N values of −15.5‰ and 11.5‰, respectively. Generally, people mainly consumed animal products and possibly milk/dairy products as well as various cereals including millet and wheat/barley. Little dietary variance occurred over time. Inferred subsistence strategies in Goukou include herding, farming, and hunting. There is evidence that cultural exchange between East and West as well as local environmental conditions contributed to the formation and development of multiple economic practices in Goukou.

Vegetation and climate history of Anggertu Lake in the Tengger Desert over the last millennium

Reconstructing climate change of the last millennium is important to understand the current relationship between human-social activities and natural environmental changes. Pollen assemblages, losson-ignition (LOIorg at 550°C), and grain size data collected from sediment core AGE15A from the center of Anggertu lake (eastern Tengger Desert, Inner Mongolia) were used to reconstruct the regional vegetation and climate history of the last millennium. Desert or steppe desert, dominated by Artemisia and Amaranthaceae, expanded around this region during the period of 988–1437 AD indicating a generally dry climate condition with two short humid periods (1003–1082 AD and 1388–1437 AD). These two wet periods were characterized by relatively high vegetation cover and bioproductivity, as reflected by high pollen concentrations and LOIorg values. Increases in steppe and meadow vegetation communities (Poaceae, Cyperaceae) and vegetation cover during 1437–2015 AD suggest a wetting trend, which was also deduced from a gradual trend towards fine grains and higher lake biological productivity as reflected by LOIorg values. An unstable lacustrine environment was identified via frequent fluctuations in pollen concentration and grain size after 1842 AD. This study also recorded a relatively dry Medieval Warm Period (MWP, 1082–1388 AD) and a wet Little Ice Age (LIA, 1437–1842 AD). Increased Amaranthaceae and high abundance of Poaceae may be related to overgrazing and agricultural activities that took place during those time periods. The evolution of vegetation in the lake region was influenced by climate change and human activities. These results could provide more fundamental support for studies of the environmental evolution of the Tengger Desert.