Sunday 10 November 2019

Investigating the origins of sedentism and plant cultivation in northeast China.

The transition to a sedentary way of life and the domestication of plants is arguably the most significant ‘revolution’ in human history. This transition gradually resulted in a dramatic increase of population size and density, in craft specialisation and the division of labour and the initiation of social dynamics and the accumulation of resources that are linked to the development of socio-political stratification. The processes, mechanisms and possible drivers of a transition from one subsistence mode to another have long been at the forefront of anthropological and archaeological research. Three hypotheses have been proposed to explain such transitions. The first suggests that stress, induced either by deteriorating environmental conditions (the ‘oasis hypothesis’) or by population increase led to an overexploitation of the environment and forced innovation. A current example is the optimal foraging theory and the diet breadth model, which predict that a transition to a delayed returns system (i.e. long-term tending resources) will occur during times of scarce resources, promoting a border dietary range. The second hypothesis argues that transitions occur at times of enhanced resources. A current example is the cultural niche construction theory, which claims that organisms shape their environment during stable or affluent times, these allow experimentation with locally available resources, which improve crop yield and eventually lead to domestication. The third hypothesis argues that transitions occur as a result of socioeconomic competition and are not affected by external forcings.

In a paper published in the journal PLoS One on 18 July 2019, Gideon Shelach-Lavi of the Department of Asian Studies at The Hebrew University of Jerusalem, and the Center for Frontier Archaeology at Jilin University, Mingyu Teng, also of the Center for Frontier Archaeology at Jilin University, Yonaton Goldsmith of the Department of Geological and Planetary Sciences at the California Institute of Technology, and the Institute of Earth Sciences at The Hebrew University of Jerusalem, Ido Wachtel of the Department of Archaeology at The Hebrew University of Jerusalem, Chris Stevens of the Institute of Archaeology at University College London, Ofer Marder of the Department of Bible Studies at Ben-Gurion University, Xiongfei Wan of the Institute of Archaeology and Cultural Relics, Xiaohong Wu of the School of Archaeology and Museology at Peking University, Dongdong Tu, again of the Department of Asian Studies ar The Hebrew University of Jerusalem, Roi Shavit, also of the Department of Bible Studies at Ben-Gurion University, Pratigya Polissar of the Lamont Doherty Earth Observatory, Hai Xu of the Institute of Surface-Earth System Science at Tianjin University, and Dorian Fuller, also of the Institute of Archaeology at University College London, present evidence for the timing, duration and environmental conditions of the onset of sedentism and plant cultivation in northern China, the second oldest center of domestication in the Old World.

Shelach-Levi et al. address the first two hypotheses by examining whether the onset of sedentism and cultivation occurred at a time of stress or affluent conditions and whether these environmental conditions were stable or fluctuating. They assume that the limiting environmental parameter is rainfall and thus we focus on the timing of rainfall changes and human settlement patterns at the onset of sedentism and cultivation in north China. They acknowledge the possibility that temperature might have also played a role in restricting Millet growth, however, as the magnitude, timing and seasonal structure of temperature change in north China in uncertain, they focus on rainfall. The combination of high-resolution archaeological and palaeoclimatic data enable to test the theoretical frameworks of the onset of sedentism, domestication and population increase.

North China is one of a few centres in the world where complex agricultural systems emerged independently. The native staple grains are two types of Millet (Foxtail and Broomcorn), however, the date, process and the palaeoclimatic context of their domestication are debated. Shelach-Levi et al. focus on northeast China because currently the earliest undisputed examples of domesticated Millet grains and the most extensive evidence for early Millet consumption have been found in this region, at sites of the Xinglongwa culture.

Early research in north China began in the 1970s and focused on the middle reaches of the Yellow River. It identified remains of early Neolithic sedentary societies of the 7th and 6th millennia BC, which were sorted into a series of ‘cultures’, most notably Cishan and Peiligang. These findings focused attention to this area – which classical Chinese tradition identifies as ‘the cradle of Chinese civilization’, the birthplace of agriculture from whence it spread to other regions in north and central China. By the late 1980s, it became clear that contemporaneous sedentary societies also existed in other regions of north China, including the Houli culture in the lower Yellow River area and the Xinglongwa culture in Northeast China. In recent years even earlier phases of the 'Neolithic' period were identified in the different sub-regions of North China, such as the Xiaohexi phase in the northeast, but those are not well studied and are poorly dated. While substantial archaeological knowledge of sedentary prehistoric societies has been presented, the earlier phases that preceded the sedentary cultures and the transition process from mobile to sedentary societies remains mostly obscure. To address these developments and their context during the important phase of the transition to agriculture, Shelach-Levi et al. integrate novel data from the excavations of two early Neolithic sites, the results of two high-resolution archaeological surveys in northeast China and novel palaeoclimatic data.

Over the past 20 years, four high-resolution, detailed, large-scale regional archaeological surveys have been conducted in northeast China. Shelach-Levi et al. focus on the surveys conducted around the modern cities of Chifeng, in Inner Mongolia, and Fuxin, in Liaoning Province, because these are the only surveys that recovered evidence of the earlier phases of sedentism. These surveys were designed to systematically recover data that enable population estimates and the reconstruction of local socio-political trajectories. The full area was systematically surveyed on foot (at a 50 and 20 m resolution), the locations and densities of pottery shards and stone tools were mapped, counted and statistically analyzed. A total pottery amount was calculated for each period by integrating the area of the occupied territory, the density of artifacts and the length of each period. These results provide a direct reconstruction of population trajectory in these two regions and present a qualitative demographic history of northeast China. The earliest sites found in both regions are those attributed to the Xiaohexi phase and the Xinglongwa culture, which represents the earliest phase of sedentism in this region. The combined results of the two surveys demonstrate a rapid increase in population and the complexity of village society following the initial stage of sedentism.

Map of the survey areas and the palaeoclimate records discussed. Shelach-Levi et al. (2019).

To evaluate the timing and socio-economic processes involved in the transition to sedentism, Shelach-Levi et al. excavated two single-occupation sites discovered during our survey in the Fuxin area. Those sites capture the onset and earliest phases of sedentism.

At the earlier site, 12D56 (also named Jiajiagou west site 贾家沟西遗址), the excavation exposed a single-occupation, irregular-oval structure of ~3.5 m in diameter, which contained ash, pottery and stone tools. Based on seven ¹⁴C ages, the site was occupied between 7900 and 7750 years ago (5900-5750 BC). This is the first time that a Xiaohexi phase site is radiocarbon dated. Previous research, based on ceramic typology, suggest dates in the 7th and even 8th millennium BC, but according to Shelach-Levi et al.'s findings the date of this phase cannot be earlier than 6,000 BC. The shape of the structure we excavated is also different from the supposedly rectangular structures reported for some Xiaohexi sites. At some of those sites the rectangular structures may belong to a later Xinglongwa occupation and in others the report is not detailed enough to examine the shape of the structures. Thus, it is possible that in other sites as well, structures were oval or that both oval and rectangular shape structure existed during this period.

The 12D56 site. Plans of the excavation site showing the structures excavated (solid lines are places where the perimeter of the structure was excavated, dashed lines represent extrapolation of the structure parameter and are provided as context reference, shading is pottery density (shard/m²). Shelach-Levi et al. (2019).

About three hundred potshards were excavated from this site. There are are crude, soft and crumbly, similar in style and quality to those known from other Xiaohexi sites. Most shards are unadorned, but a few pots are decorated with appliqué and narrow bands of diagonal incisions. 330 stone artifacts were also recovered, including ground and chipped stone tools. Of the ground stone tools, almost 80% are spades. Although no use-wear analysis was done, the fact that those artifacts, which are not known from earlier periods in the region, are so dominate suggest that they are associated with new set of activities, probably related to the clearance of woods and the cultivation of the land Similar artifacts are known form other site dated to the Xiaohexi phase.

Artifacts excavated at site 12D56. Stone artifacts (upper half) and pot shards (lower half). Shelach-Levi et al. (2019).

Floral remains from the site consist of a predominance of wild fruits and nuts and a small amount of wild Panicum Millet (Panicum miliaceum ruderale). The two seeds that were recovered are small in size and are representative of what is expected of grains from early cultivated plants in the initial process of domestication.

At the later site, 12D16 (also named Tachiyingzi site 塔尺营子遗址), Shelach-Levi et al. excavated an area of ~40 m² out of a much larger site. Based on ten ¹⁴C ages, the site was occupied between 7.5–7.4  thousand years ago (5500-5400 BC). The area excavated contained a rectangular structure measuring about 7.5 × 6.5 m and remains of at least one additional structure. The shape of the structure is identical to those known from the nearby site of Chahi (查海), where a large area of the site was exposed revealing a densely occupied Xinglongwa period village.

The 12D16 site. Plans of the excavation site showing the structures excavated (solid lines are places where the perimeter of the structure was excavated, dashed lines represent extrapolation of the structure parameter and are provided as context reference, shading is pottery density (shard/m²). Shelach-Levi et al. (2019).

The structure in this area was severely burned during or after its abandonment and remains found on its floor indicate that it was supported and covered with large oak beams. On its floor Shelach-Levi et al. recovered 22 complete ceramic vessels of typical Xinglongwa culture. The quality of ceramic production is high and most are highly decorated with incised motifs. The stone artifacts are more abundant and diverse than those of site 12D56 (1003 such artifacts were found at site 12D16), and show evidence for highly standardised pressure bladelets produced on-site, as a household routine. The ground stone assemblage consists of grinding stones, polished axes and adzes, spades, pounders and hammer-stones.

Artifacts excavated at site 12D16. Stone artifacts (upper half) and ceramic vessels (lower half). Shelach-Levi et al. (2019).

Floral remains include a few millet seeds but are predominantly composed of wild fruits and nuts. Sixteen millet grains are identified as Common Millet (Panicum miliaceum). Their size is small, on average 1.25–1.70 mm in length and 1.05–1.40 mm in width, closer to the wild type Panicum (Panicum miliaceum ruderale) than to modern domesticated Broomcorn. These grains seem to represent plants that are not yet fully domesticated, but represent an early phase in a sequence of size change expected to take 2–3 thousand years.

Remains of Common Millet (Panicum miliaceum) from site 12D16. Shelach-Levi et al. (2019).

To evaluate northeast China’s palaeo-hydroclimate during the transition to domestication and sedentism, Shelach-Levi et al. integrated data from Dali lake-level to provide an estimate of rainfall change, and Lianhua Cave oxygen isotopes to provide continuous, high-resolution absolute dating. In addition, they analysed the isotopic contents of soil alkanes from both archaeological sites, which primarily records the isotopic composition of rainfall. Alkanes are organic compounds produced in leaf waxes incorporating oxygen and hydrogen derived from water. These can be preserved in in soils and give a record of the ratios of different isotopes of the elements within the local water when the plant was growing. When air masses hit areas of high ground and are uplifted, they cool and preferentially precipitate moisture with the heavier isotopes of oxygen and hydrogen, thus the ratio of these isotopes in the preserved alkanes in the soil gives a measure of how high up and how far from the source water the soil was when it formed. The palaeoclimate records show similar hydroclimate patterns. Between 9000 and 8100 years ago (7000-6100 BC) relatively dry conditions prevailed in northeast China. Between 8100 and 7900 years ago (6100-5900 BC) a sharp substantial increase in rainfall amount occurred. The Lianhua Cave record shows a 2.5‰ (2.5 parts per thousand) isotope change at 8100 years ago (6100 BC), which is only comparable in magnitude to the transition from the Younger Dryas to the Early Holocene at 11 500 years ago (9500 BC). The soil alkanes are more depleted in heavy isotopes at the later 12D16 site than the the earlier 12D56 site and is thus in agreement with the other records. The relatively wet conditions prevailed for  about 400 years. A decrease in rainfall amount occurred between 7550 and 7400 years ago (5550-5400 BC). This transition appears in both records, though the timing of the rainfall decline differs by about 150 years.

The onset of sedentism, cultivation and the early phase of domestication in northeast China is an important test case for studying the theoretical frameworks for the transition to agriculture. The transition to sedentism in the Xiaohexi phase is defined by investment in permanent structures, unknown in this region in prior periods, the dramatic increase in the production of pottery found at all sites in relatively large quantities, and the presence of large grinding stones. The empirical coincidence of the onset of sedentism and cultivation about 7900 years ago (5900 BC) with the transition to a significantly wetter climate between 8100 and 7900 years ago (6100-5900 BC) suggests that affluent conditions played an important role in facilitating the onset of these processes in northeast China. Shelach-Levi et al.'s results suggest that in northeast China, fundamental and multi-scale changes occurred not due to necessity or stress but rather under stress-free affluent conditions and thus support the affluency hypothesis. Such plentiful resources allowed Human communities to settle down in one place and enhance their interaction with their immediate environment, without the need to migrate in search of food.

The Xinglongwa culture thrived throughout this affluent period and declined within a century from the end of the wetter condition. This strengthens the notion that affluent climatic conditions were an important factor in the ability of this culture to thrive.

Sedentism and plant cultivation initiated simultaneously, but sedentism and the development of a complex village society matured much faster. The initial phase of sedentism, in the Xiaohexi phase is typified by small sites with makeshift irregular-shaped huts, which suggest low investment in construction and perhaps short life-use. This phase rapidly transitioned into the full-fledged Xinglongwa culture in which large scale-villages containing up to 40 domestic structures, represent an increase in community size that coincided with a rapid increase of regional population levels. Rectangular domestic structures, like the one excavated at site 12D16, and community-wide projects, such as the ditch that surrounded the Chahai site, suggest substantial investment, and communal construction efforts.

Simultaneous processes, such as the intensification of craft production and improvement of ceramic and stone tool technologies, suggest a development of craft specialisation and economic intensification. Similar developments are known from other parts of north China, suggesting that the processes described by Shelach-Levi et al. were shared by many contemporaneous societies.

The process of plant domestication progressed at a much slower pace. Elsewhere, researchers argue for an earlier date of Millet domestication and use in other regions of North China. However, because they use different types of data it is difficult to compare their results to those of Shelach-Levi et al. According to their study, evidence for its initiation (i.e. collection of plants that later will be domesticated and probably the cultivation of wild plants) is found at site 12D56, even after 500 years it was not yet completed at site 12D16. Moreover, the percentage of domesticated foods seems to have remained limited even during the height of the Xinglongwa period. Shelach-Levi et al.'s results disagree with earlier studies that found Human bone carbon isotopes from the Xinglongwa period suggestive of a grain (possibly Millet) dominated diet. Future research will be needed to resolve these contradictions. Recent evidence from other parts of North China suggest that like the process Shelach-Levi et al. describe for the Fuxin area, there too the trajectory of domestication and transition to agriculture was relatively long. In the initial phases, addressed by Shelach-Levi et al., it was not domestication per-se which was important but the cultivation of the land (indicated by the large number of spades found at site 12D56) and the harvesting and consumption of durable food resources such as seeds (of domesticated and wild plants), nuts (such as Acorn and Walnut) and wild fruits (Apricot, Amur Cork). Those resources were collected in large quantities, stored for long periods, and thus enable a year-long occupation of the same site and the stable support of larger communities. Based on the data they collected, Shelach-Levi et al. suggest that the suite of traits that found in the earliest phase sedentism, expansion into new types of food resources and perhaps cultivation, were the driving force behind domestication and not vice-versa.

The archaeological, botanical and palaeoclimatic data presented above help clarify the context of the transition to a sedentary way of life, plant cultivation and initial stages of plant domestication in Northeast China. The multi-dimensional nature of Shelach-Levi et al.'s data allow them to suggest that these processes occurred during a period of comparative affluence that enabled population increase and experimentation with new resources and technologies. Our botanical findings support the view that the domestication process took a long time after Humans started cultivating plants, as has been demonstrated for several other crops in other regions, and that not all the plants that were initially cultivated or intensively collected were botanically transformed and became domesticated. These observations, which may not be true for all cases of independent transitions to sedentary agricultural societies, are crucial for a global view of the evolution of Human society. They suggest that at least in some cases, fundamental and multi-scale changes occurred not due to necessity or under stress but rather because of opportunities to experiment and expand under stress-free affluent conditions.

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