New evidence supports the continuous development of rice cultivation and early formation of mixed farming in the Middle Han River Valley,China

Abstract

Located in the transitional region between northern and southern China, the middle Han River valley is of pivotal significance for current debates on rice domestication and the formation of mixed farming in early China. Based on phytoliths and macro-plant remains from 10 sites, along with radiocarbon dating, this study has narrowed the 2000-year gap in early rice utilization by 700 years in the middle Han River valley, and demonstrated the continuous development of rice agriculture in this region. This new evidence also reveals that as early as 7000 cal. BP, mixed farming emerged in this region and facilitated the further southward dispersal of foxtail millet and broomcorn millet into southern China and beyond. In addition, a sample-by-sample comparison of our results with phytoliths and macro-plant remains highlighted the potential biases inherent in these methods. This work emphasized the importance of multi-index archaeobotanical analysis to reconstruct ancient crop assemblages.

Keywords

macro-plant remains mixed farming Nanyang basin phytolith rice domestication

Introduction

The emergence of agriculture is of profound significance in human history as it has drastically changed the lifestyle and social organization of human beings and eventually led to the emergence of civilizations in different parts of the world (Bellwood, 2005; Childe, 1936; Fuller and Stevens, 2019). As a critical region for investigating agriculture origins, China has attracted worldwide attention in past decades (Diamond, 2002; Fuller et al., 2014; Larson et al., 2014). Recent studies have confirmed that foxtail millet (Setaria italica) and broomcorn millet (Panicum miliaceum) were domesticated in northern China and rice (Oryza sativa) in southern China (Deng et al., 2015; Larson et al., 2014; Lu, 2017; Lu et al., 2009b; Yang et al., 2012). Subsequently, interactions between these two regions facilitated the formation of a dualistic farming tradition in a vast area of China (Deng et al., 2018a; He et al., 2017), which then dispersed southward into Southeast Asia and beyond, to profoundly influence subsequent social developments in these regions (Gao et al., 2020). Therefore, the pathway of crop domestication and the formation of mixed farming in China is central to the study of early agricultural practices. Targeted research on this topic significantly could improve our knowledge of agricultural origins and interactions in the world.

Previous archaeobotanical evidence has generally revealed that the domestication of both millet and rice could be traced back to more than 8000 years ago (Lu, 2017; Qin, 2012). Regarding the domestication of rice, the core areas of the middle and lower Yangtze region have been widely accepted as its domestication center since the 1980s (Huan et al., 2021; Yan, 1982, 1989a; Zheng et al., 2016; Zhijun, 1998; Zuo et al., 2017). However, a growing number of discoveries in the past few years have suggested that since around 8000 cal. BP or even earlier, rice was utilized in many other regions outside of the proposed center, such as the Huai River valley (8500–8000 cal. BP) (Luo et al., 2016, 2021; Zhang et al., 2018; Zhao and Zhang, 2009), the middle Han River valley (8600–8300 cal. BP) (Deng et al., 2015), and Shandong Province (8000–7700 cal. BP) (Crawford et al., 2016; Jin et al., 2014). With these lines of new evidence, numerous scholars have raised debates around the model of rice domestication (Choi et al., 2017; Qin, 2012; Silva et al., 2015; Stevens et al., 2016). These ideas can generally be categorized into two major groups: namely the mosaic model and the core area model. The former argues that other regions like the Han River valley, the Huai River valley, and even Shandong Province have played a non-negligible role in the process of rice domestication, especially with the discovery of fully domesticated rice dating back to 8600 cal. BP in Baligang and Jiahu (Allaby et al., 2017; Deng et al., 2015; Zhang et al., 2018; Zhao and Zhang, 2009). By contrast, the latter treats the early utilization of rice in these regions out of the core area of the middle and lower Yangtze valley as dead ends, because there is no solid evidence for the continuation of rice agriculture in the following one or two thousand years (Qin, 2012). In this case, the evidence for the continuation of rice farming around 8000–6500 cal. BP in these ambiguous origin centers, such as the middle Han River valley and the Huai River valley, is of critical importance in resolving these debates.

Regarding the formation of the dualistic farming regime in early China, the Song Mountain area of central China (mainly including modern Zhengzhou, Luoyang, Xuchang, and Pingdingshan) is the region with the earliest direct evidence known to date. As demonstrated by plant remains from Zhuzhai (Bestel et al., 2018; Wang et al., 2018) and Tanghu (Zhang et al., 2012), rice had spread into this region no later than 7500 cal. BP and was cultivated along with indigenous foxtail millet and broomcorn millet. The emergence of rice agriculture here should be closely related to communications with the adjacent middle Han River Valley or the middle Huai River Valley. Meanwhile, evidence of southward dispersal of broomcorn millet has been reported from the Shuangdun site in the middle Huai River valley around 7000–6800 cal. BP (Luo et al., 2019). However, in the middle Han River valley, the earliest evidence of millet cultivation is only around 6300 cal. BP from the Baligang site (Deng et al., 2015), which is much later than the first appearance of rice in the Song Mountain area and broomcorn millet at the Shuangdun site. Therefore, to investigate the beginning of the southward dispersal of millets, systematic archaeobotanical work is still required in these related regions, especially the middle Han River valley.

As stated above, the middle Han River valley is of critical significance for the study of rice domestication and the investigation of the southward dispersal of millets. Direct evidence of farming practice between 8300 and 6300 cal. BP is required to detect whether rice agriculture continued during this period and to investigate when millets were introduced into this region. In this regard, 10 archeological sites expanding from the early to late Yangshao period in the Nanyang Basin were surveyed and sampled. Based on analyses of phytolith and macro-plant remains, together with accelerator mass spectrometry (AMS) radiocarbon dating, this study reveals that mixed farming had primarily emerged in this region as early as almost 7000 cal. BP and that it continued in later periods. This new evidence also significantly reduces the gap in rice agriculture development in this region by nearly 700 years, indicating the continuous development of early rice agriculture.

Materials and methods

Sample collection

In 2019, 10 archeological sites of the Yangshao period in the Nanyang Basin of the middle Han River valley were investigated and sampled (Figure 1). These sites are distributed in different parts of the basin, with diverse landforms and climatic conditions. Samples for flotation and phytolith analyses were collected from exposed cultural deposits on natural profiles by context. Considering the possible uneven distribution of phytoliths in the cultural deposits, at least two parallel samples of the same context were collected for phytolith analysis. According to this standard, 56 phytolith samples and 32 flotation samples (394 L) were collected from 24 contexts of the 10 sites (Supplemental Material Table S1, available online). Specifically, in the early Yangshao period, 12 phytolith analysis samples and 5 flotation samples (70 L) were collected from the Dazhangzhuang site. In the middle Yangshao period, six phytolith samples and five flotation samples (68 L) were collected from the Xianghuazhai site. Finally, in the late Yangshao period, 22 phytolith samples and 40 flotation samples (256 L) were collected from eight sites.

Figure 1.

Locations of studied sites in Nanyang basin and other sites mentioned in this study (FD-Dazhangzhuang, NZ-Zhaishang, NM-Miaopo, NL-Licun, ZZS-Zhongshangsi, ZZW-Zhongwa, ZA-Anguocheng, DT-Taizigang, NC-Chaan, NX-Xianghuazhai).

To detect the exact date of the studied contexts, 13 samples from seven sites were sent to Beta Analytic Testing Laboratory for direct AMS radiocarbon dating, of which eight were rice grain fragments, two were fruit husk fragments, one consisted of 10 foxtail millet grains, and two were charcoal samples. The details of the dated samples are presented in Table 1.

Table 1.

AMS radiocarbon dating results from the sites of Nanyang Basin (All dates are calibrated by OxCal v4.4, using the IntCal 20 Atmospheric curve).

Site	Lab code	Context no.	Dated material	Uncalibrated C-14 date BP	Calibrated dates (2σ) BP
Dazhangzhuang	Beta-583416	FDH1①	Charcoal	5980 ± 30	6933–6733
	Beta-583417	FDH1②	Fruit husk	5950 ± 30	6880–6675
	Beta-583418	FDH2	Charcoal	5730 ± 30	6630–6412
Xianghuazhai	Beta-583425	NXH1	Rice frags	5120 ± 30	5934–5750
Xianghuazhai	Beta-583424	NXP2	Rice frags	4880 ± 30	5705–5488
Cha’an	Beta-583421	NCP2	Foxtail millet	4650 ± 30	5572–5321
Anguocheng	Beta-583429	ZAP3	Rice frags	4700 ± 30	5462–5416
Zhongshangsi	Beta-583430	ZZSP1	Fruit husk	4610 ± 30	5465–5314
Zhongwa	Beta-583426	ZZWP1	Rice frags	4520 ± 30	5309–5050
	Beta-583427	ZZWP2	Rice frags	4520 ± 30	5309–5050
	Beta-583428	ZZWP3	Rice frags	4420 ± 30	5271–4870
Licun	Beta-583422	NLP2②	Rice frags	4550 ± 30	5320–5051
Licun	Beta-583423	NLP3	Rice frags	4550 ± 30	5320–5051

Extraction and identification of macro-plant remains

All samples were floated on-site using flotation buckets. Plant remains were collected by sieves (0.3 mm) and sent to the Archaeobotany Lab of the School of Archaeology and Museology at Peking University for further analysis after being dried in shade. Seeds, fruits, and other plant remains in each sample were sorted, classified, identified, and counted under a stereomicroscope by referring to modern collections and atlases of modern seeds (Cappers and Bekker, 2013; Guo, 2009; Nesbitt, 2005), while the charcoal samples were not analyzed further. In particular, foxtail millet and broomcorn millet grains were further classified into mature, immature, and very immature types according to previously established criteria (Deng et al., 2021; Song et al., 2013).

Phytolith extraction and identification

Phytoliths were extracted from soil samples according to established methods (Lu et al., 2002; Piperno, 1988) with minor modifications. Initially, approximately 2 g of each sample was weighed and treated with 30% H₂O₂ and 15% HCl to remove organic matter and carbonates. The samples were then subjected to heavy liquid flotation using ZnBr₂ (density, 2.35 g/cm³) to separate the phytoliths, which were subsequently mounted on a slide using Canada Balsam. After air drying, the phytoliths on the slide were identified and counted using a Leica microscope at 400× magnification. More than 400 phytolith particles in each sample were identified and recorded according to published references and criteria (Ge et al., 2018, 2019, 2020a; Lu et al., 2006, 2007, 2009a; Wang and Lu, 1993). In particular, for samples with rice phytoliths, the slides were scanned until 50 rice bulliform phytoliths with clear and countable scales were observed in order to calculate the proportion of rice bulliform phytoliths with ⩾9 scales (Huan et al., 2015; Wang and Lu, 2012). Previous criteria have suggested that this value is only 17.86 ± 8.29% in wild rice soil samples and 63.7 ± 9.22% in soil samples from domesticated rice paddies (Huan et al., 2015). Applying these criteria in archeological sites of different regions clearly indicates that it could provide valuable information on rice domestication (Deng et al., 2018b, 2020b; Luo et al., 2016; Ma et al., 2016, 2018).

Results

Radiocarbon dating results

All 13 dating samples from the seven sites successfully yielded radiocarbon dates. These dates were calibrated by OxCal 4.4, using the IntCal 20 atmospheric curve (Reimer et al., 2020), and are presented in Table 1. Generally, all these direct dates fit well with the cultural affiliations of their contexts. The results of Dazhangzhuang and Xianghuazhai are ca. 7000–6500 and 6000–5500 cal. BP, falling within the time span of the early and middle phases of the Yangshao culture (Institute of Archaeology Chinese Academy of Social Sciences, 2010; Yan, 1989; Zhang et al., 2013). The dating results of the other five sites are concentrated in ca. 5500–5000 cal. BP, within the time span of the late Yangshao period. Considering the previous Yangshao archaeobotanical data from Baligang in this region are concentrated in ca. 6300–5900 cal. BP, a complete chronology of Yangshao farming practice in the middle Han River valley, could be built with these new data.

Results of macro-plant remains

Plant remains were well-preserved in most sites sampled in this study. Only the three contexts of Dazhangzhuang produced no macro-plant remain, except for charcoal and unidentifiable fruit husk fragments. A total of 7913 seeds and other parts of plant remains (including fragments) were found at the other nine sites. According to the preservation conditions of these remains, 1260 uncarbonized plant remains were considered to be yielded from later intrusions and excluded in the further statistical analysis of this study (Figure 2). The density of the plant remains varied significantly across different contexts. The highest density was observed at the Xianghuazhai site, with nearly 320 specimens per liter, while the densities found at other sites were generally less than 20 specimens per liter.

Figure 2.

Proportions of main plant categories in assemblage of each context sampled in this study.

Twenty-six taxa of plants were identified at the species, genera, or family level for all samples. In addition, a few other weed seeds remain unidentified. Generally, all the remains can be classified into four categories, namely crops, fruits, grasses, and other weeds (Figure 2). The crops, including rice (Oryza sativa), foxtail millet (Setaria italica), and broomcorn millet (Panicum miliaceum) (Figure 3), accounted for the highest proportion in the assemblage of macro-plant remains. For fruits, Vitis sp., Diospyros sp., Crataegus sp., Sambucus sp., and other unidentifiable husk fragments were recovered. The numbers of fruits were very low in all samples, and only one or two specimens were found for each taxon. Setaria sp., Digitaria sp., and Echinochloa sp. were the common grasses found in these samples, while other Panicoideae seeds also appeared. The number of Portulacaceae, Brassicaceae, Molluginaceae, and Fimbristylis sp. were relatively high, and the numbers of other taxa of weeds usually were less than 10.

Figure 3.

Crop phytoliths and macro-remains obtained from Nanyang Basin samples: (a and b) rice bulliform with <9 scales, (c and d) rice bulliform with ⩾9 scales, (e–g) rice double-peaked phytolith, (h) rice parallel-bilobate, (i and j) broomcorn millet η type, (k) rice double-peaked (blue arrow) and broomcorn millet η type (orange arrow), (l and m) foxtail millet Ω type, (n) rice double-peaked (blue arrow) and foxtail millet Ω type (yellow arrow), (o) foxtail millet, (p) broomcorn millet, (q) rice grain, (r) rice embryo, (s) rice spikelet base (non-shattering type), (t) rice spikelet base (unidentifiable type), and (u) rice spikelet base (protruding type) (scale bar: a–m = 20 μm; o–q = 1 mm; r–u = 0.2 mm).

Phytolith results

All 56 samples from 10 sites yielded abundant phytoliths. In total, 26 phytolith morphotypes were identified. Five could be confirmed from crops, including double-peaked, bulliform, and parallel-bilobate types from rice, η-type epidermal long cell phytolith from upper lemma, palea of broomcorn millet, and Ω-type from foxtail millet (Figure 3). Other main phytolith types include square, bulliform, smooth elongate, rectangle, acicular hair cell, rondel, reed bulliform, bilobate, trapeziform sinuate, and so forth. A “paired-samples T Test” of phytolith assemblages of parallel samples in each context using SPSS 23 suggested that all the correlation coefficients of the parallel samples were higher than 0.817 and all p (Sig. (two-tailed)) = 1 > 0.05, indicating no significant differences.

Phytolith assemblages of the early Yangshao samples were characterized by high proportions of rondel, bulliform, square, rectangle, and woody types, along with relatively low proportions of rice and broomcorn millet morphotypes (Figure 4). Foxtail millet Ω-type phytoliths first appeared in the mid-Yangshao period, but their proportions were much lower than those of broomcorn millet and rice. It is also worth noting that nearly all mid-Yangshao samples from the Xianghuazhai site were characterized by high proportions of double-peaked types of rice husk, revealing a strong relationship between cultural deposits in these contexts and rice dehusking activities at the site. In the late Yangshao period, the major phytoliths were bilobate, elongate psilate, and rice double-peaked at all sites. The proportions of foxtail millet and broomcorn millet varied greatly among different sites but were much lower than rice overall.

Figure 4.

Percentage diagram of major phytolith types in all samples of the Nanyang Basin.

Based on the preservation conditions, 26 samples were selected for further analysis of scales on the edge of rice bulliform phytoliths, including 12 from the early Yangshao period, two from the mid-Yangshao period, and 12 from the late Yangshao period (Figure 4). At least 50 bulliform phytoliths with clear and countable scales were carefully observed for each sample. The proportion of bulliform phytoliths with ⩾9 scales was within the range of 27.5%–44.0% in the early Yangshao period, 44.0%–48.0% in the mid-Yangshao period, and 38.0%–56.0% in the late Yangshao period.

Discussion

The critical role of the middle Han River valley in the process of rice domestication

Located in the transitional region between north and south China, the middle Han River valley constitutes part of the northernmost edge of rice utilization prior to 8000 cal. BP and is of great importance in the discussion of rice agriculture origin models. Nevertheless, archaeobotanical studies in this region are limited, where Baligang is the only site with systematic data of plant remains (Deng et al., 2015; Weisskopf et al., 2015). The currently available data from Baligang are mainly concentrated in four discontinuous periods, namely 8600–8300 , 6300–5900 , 5000–3800 , and 3000–2200 cal. BP. The gap between these periods, especially the first two around 8300–6300 and 5900–5000 cal. BP strongly has influenced our understanding of early rice agriculture development in this region.

The new data presented in this study have served to fill these gaps, helping complete the early chronology of rice farming development in this region. Phytolith remains from the 10 sites studied, along with previous evidence from Baligang, demonstrate that rice was utilized by local people continuously from 7000 to 5000 cal. BP (Figure 4). The most important discovery here is that phytoliths originating from rice leaves, stems, and glume cells were present in all samples of Dazhangzhuang (7000–6500 cal. BP). This new discovery extends the evidence of rice utilization in the Yangshao period of this region from 6300 to 7000 cal. BP, filling the early gap in rice farming development by 700 years.

Owing to the poor preservation conditions of macro-plant remains at Dazhangzhuang, no crop seeds, spikelet bases, or other remains have been obtained from the early Yangshao period, while solid evidence of rice grains, spikelet bases, and husk fragments was abundant in the middle and late Yangshao samples. Morphological classification of rice spikelet bases (Fuller et al., 2009) revealed that, except for sparse specimens of protruding type and unidentifiable ones, 98.3% rice spikelet bases from these sites were non-shattering types, demonstrating that they were fully domesticated, similar to the Baligang ones (Deng et al., 2015).

In contrast to the estimation based on spikelet bases, the analysis of scale numbers on the edge of rice bulliform phytoliths suggests a more complex condition. Although the proportions of rice bulliform phytoliths with ⩾9 scales in all samples were evidently higher than the level found in modern wild rice (Huan et al., 2015), they were also much lower than the level found in modern domesticated rice (Huan et al., 2020) (Figure 5) and those found in late Neolithic sites of other regions (Deng et al., 2018b, 2020b; Ma et al., 2016, 2018). Furthermore, even in the middle and late Yangshao samples, the proportions were generally lower than 50%, which contradicts the results of spikelet bases. Similar conditions were also observed at the Zhangwangzhuang site of the Huai River valley, where the proportions were lower than 40% in the early Yangshao period (Huan et al., 2022). The main reason for this ambiguous condition is that the mechanism controlling the number of scales on the edge of rice bulliform phytoliths is still unclear. This is possibly related to some special farming regimes that could have influenced water conditions in different stages of the rice-growing season, while the cultivation technologies in different regions were distinct from each other in ancient times. In any case, this study reveals that more basic research still will be needed to improve rice phytolith identification criteria and to explore the related biological mechanisms.

Figure 5.

Proportions of rice bulliform phytoliths with ⩾9 scales in Yangshao samples of the Nanyang Basin (Modern references (Huan et al., 2015, 2020)).

To sum up, new data presented in this study, for the first time, demonstrated a continuous process of rice agriculture development out of the core area of middle and lower Yangtze valley since 8600 cal. BP, along with the previous published Baligang data (Deng et al., 2015). The middle Han River valley thus should also be listed as the potential origin centers of rice agriculture, together with core areas of the middle and lower Yangtze valley. With this new progress, more discoveries could also be expected in other regions, such as the upper Huai River valley and the lower Huai River valley. On the other hand, solid evidence of rice utilization during 10,000–9000 cal. BP has only been found in the lower Yangtze valley. But according to current evidence, fully domesticated rice here appeared much later than in other regions, around 6000 cal. BP (Gao, 2017). In this condition, a mosaic model of rice domestication is more reasonable, and it would be further supported, if earlier evidence of rice utilization could be found in the middle Han River valley and the Huai River valley (Figure 6). Whereas, the possibility of the core area model of rice domestication and fast spread into a wide area should not be completely excluded, especially if earlier evidence of fully domesticated rice (9000 cal. BP or earlier) could be found in the lower Yangtze valley and the absence of early rice utilization in other regions could be confirmed in the future. Therefore, more work is needed for the final resolution of current disputes regarding rice domestication.

Figure 6.

Potential rice domestication centers and sites with evidence of rice utilization prior to 8000 cal. BP in China (1. Shangshan, 2. Miaoshan, 3. Huxi, 4. Hehuashan, 5. Qiaotou, 6. Xiaohuangshan, 7. Kuahuqiao, 8. Jingtoushan, 9. Jiahu, 10. Baligang, 11. Pengtoushan, 12. Bashidang, 13. Yuezhuang, 14. Xihe, 15. Shunshanji, 16. Hanjing, 17. Xuenan).

The emergence and primary development of mixed farming in the middle Han River valley

With the accumulation of archaeobotanical data in southern China, the contribution of mixed farming to early social development in different regions has been widely demonstrated in the past few years (Dai et al., 2021; Deng et al., 2018a, 2020a, 2022). The channel connecting the middle Yangtze region and the Song Mountain area possibly played a significant role in the formation of this dualistic tradition, with rice spreading northward and millets southward. At least as early as 5800 cal. BP, foxtail millet appeared to the south of the Yangtze River, as evidenced by discoveries from the Chengtoushan site (Nasu et al., 2007, 2012). Subsequently, this strategy was continuously inherited in this region and spread southward into a wide range of regions comprising Jiangxi Province, the southeast coast of China, and Southeast Asia (Dai et al., 2021; Deng et al., 2018a, 2020a; Stevens and Fuller, 2017). However, the formation process of this farming regime in these related regions remains unclear because of limited evidence along the dispersal route, particularly in the middle and lower Han River valleys.

The discovery of typical η-type phytoliths of broomcorn millet together with rice remains from the Dazhangzhuang site suggests that mixed farming had already appeared in the Nanyang Basin of the middle Han River valley around 7000 cal. BP. This is almost as early as the discovery of Shuangdun in the Huai River valley (Luo et al., 2019). Thereafter, both phytoliths and macro-plant remains suggest that foxtail millet, broomcorn millet, and rice were widely cultivated in the Nanyang Basin from 6000 to 5000 cal. BP. Together with previous evidence from Baligang (Deng et al., 2015), it could be confirmed that mixed farming had been practiced continuously here at least since 7000 cal. BP.

As for the further southward dispersal of this crop package, archaeobotanical evidence prior to 6000 cal. BP was absent in the lower Han River valley. Currently, the earliest direct evidence of mixed farming in this region is from the Qujialing site, which is dated as early as 5600 cal. BP (Yao et al., 2019). Nevertheless, typological comparisons of pottery and other cultural remains suggest a strong influence and possible southward human migration from the Nanyang Basin into the Jianghan Plain around 7000–6000 cal. BP, such as the discoveries from Bianfan and Diaolongbei (Institute of Archaeology Chinese Academy of Social Sciences, 2006; Zhang, 1982). Therefore, it is quite possible that interactions between the middle Yangtze valley and central China facilitated the southward dispersal of mixed farming practices to the central part of the middle Yangtze valley around 7000 cal. BP, much earlier than we had previously thought.

Overall, with the new evidence obtained in this study, a complete chronology of agricultural development could be established. Around 8600–8300 cal. BP, rice had already been cultivated, together with the collection of acorns and possibly other wild resources (Deng et al., 2015). At least as early as 7000 cal. BP or earlier, millets spread into this region and contributed to the formation of mixed farming. This strategy probably dispersed southward into the lower Han River valley during the early Yangshao period with human migration in this period, instigating mixed farming practices in Southern China. These discoveries clearly demonstrate the critical role of the middle Han River valley in the formation and dispersal of mixed farming in early China.

Crop patterns in the Yangshao period of the middle Han River valley

For these mixed farming regions, the assemblage of crops usually is influenced by both natural and cultural factors, and the specific proportion of each crop varies greatly among different regions or periods. A previous chronological analysis of the Baligang crop patterns showed that the proportions of rice and millets were influenced by cultural changes (Deng et al., 2015). For example, millets were more important in the food supplies of Yangshao, Longshan, and Zhou Dynasties, when there was strong cultural influence from the north. By contrast, during the Qujialing and Shijiahe periods, the proportion of rice significantly increased, consistent with contemporary close cultural connections with the south. Based on evidence from more sites in the Yangshao period of the Nanyang Basin, this study provides an opportunity to examine detailed chronological changes within the Yangshao period and interregional differences in crop assemblages. Furthermore, with parallel data on macro-plant remains and phytoliths, this study could test the potential biases involved with different methods when evaluating ancient crop patterns.

In the early Yangshao period, phytoliths from Dazhangzhuang revealed that rice was cultivated by local people, along with a small portion of broomcorn millet (Figure 7). In the following middle Yangshao period, both phytoliths and macro-plant remains demonstrated that foxtail millet already had been cultivated here, and the importance of millets possibly increased (Figure 7). In samples from contexts NXP1 and NXP2 of Xianghuazhai, the proportions of millets are apparently much higher than in the early Yangshao period. The high proportions of rice husk phytoliths and spikelet bases in samples of context NXH1 were more possibly related to waste disposal during rice dehusking when compared to samples of NXP1 and NXP2. Similar conditions were also found in the late Yangshao samples from Zhongwa in Zhenping County and Zhaishang in Nanzhao County. Except for these outliers, the general crop patterns of these middle and late Yangshao sites revealed by macro-plant remains were characterized by high proportions of foxtail millet, a considerable portion of rice, and a relatively lower contribution of broomcorn millet (Figure 7). Nevertheless, phytoliths revealed a more complicated condition (see discussions below). In addition, no clear correlation between crop patterns and environmental conditions was observed in these late Yangshao sites. These new data are generally consistent with the Baligang result regarding the crop pattern in the middle and late Yangshao period, and its controlling factors are likely to be cultural traditions such as cooking methods and food preferences.

Figure 7.

Relative crop proportions of phytoliths and macro-remains during the Yangshao period.

In addition, the sample-by-sample comparison of phytoliths and macro-plant remains in this study revealed different preservation conditions of these crop remains and as such indicates possible biases when evaluating crop patterns using these methods. In simple terms, the proportions of rice and broomcorn millet in phytolith assemblages were generally higher than those in assemblages of macro-plant remains, while the proportion of foxtail millet phytoliths is normally lower than that of macro-plant remains (Figure 7). As only seeds and phytoliths from the upper lemma and palea of millet could be retrieved and identified in archeological deposits, the reason for these differences between the two indexes of foxtail millet and broomcorn millet should be attributed to the degree of preservation difficulties of these seeds and phytoliths. Modern experiments have already revealed that seeds of foxtail millet have better heat resistance and a larger temperature range for carbonization, which is much easier to preserve than broomcorn millet (Wang and Lu, 2020). On the other hand, the phytoliths produced in one broomcorn millet grain are about three times that found in one foxtail millet grain (Zhang et al., 2010). Hence, differences between the results of the two indexes could be aggravated greatly by these factors in two ways.

The condition of rice is much more complex, as many different parts of the plant can be preserved and identified. The contribution of rice bulliform and scooped bilobate phytoliths from leaves and culms would increase the proportion of rice in phytolith assemblages when compared to macro-plant remains, as these parts cannot be preserved. In samples with a high proportion of double-peaked phytoliths, the quantity of rice spikelet bases is usually relatively high. This situation will not lead to significant differences between the crop assemblages based on these two indexes when charred plants are well preserved. Otherwise, the presence of double-peaked phytoliths will also widen gaps between the results of phytoliths and macro-plant remains. In addition, both phytoliths and spikelet bases increase the relative priority of rice when compared to millets. In summary, this study reminds us that the apparent crop patterns presumed from phytoliths or macro-plant remains are influenced by complex factors. Multi-index research is needed to obtain a more reliable conclusion when dealing with these issues.

Conclusion

Our analysis of macro-plant remains and phytoliths, together with AMS radiocarbon dates from 10 sites shed new light on the primary development of early agriculture during 7000–5000 cal. BP in the middle Han River valley. Direct evidence of rice at approximately 7000 cal. BP from Dazhangzhuang cut down the previous 2000-year gap of rice utilization in this region by 700 years and demonstrated the continuous development of rice agriculture.

On the other hand, the emergence of broomcorn millet at approximately 7000 cal. BP demonstrated that mixed farming had formed in this region at least since then and continued in the following periods. Combined with previous discoveries from Baligang, the transformation of crop patterns from pure rice farming to mixed farming in this region has also been established. A detailed comparison among crop patterns at different sites revealed that the contribution of millets was possibly the same or higher than that of rice in the daily food supplies of local people in the middle and late Yangshao period, and no obvious interregional distinction was observed.

Methodologically, this study also suggests that more basic work is still needed to further improve the criteria for distinguishing wild and domesticated rice based on scale numbers on the edge of rice bulliform phytoliths. Biological mechanisms affecting this feature should also be explored accordingly. In addition, either phytolith data or macro-plant remains produce an obvious bias in the reconstruction of ancient crop assemblages. A multi-index analysis is essential in such studies to obtain more reliable results.

Supplemental Material

sj-docx-1-hol-10.1177_09596836221101253 – Supplemental material for New evidence supports the continuous development of rice cultivation and early formation of mixed farming in the Middle Han River Valley, China

Supplemental material, sj-docx-1-hol-10.1177_09596836221101253 for New evidence supports the continuous development of rice cultivation and early formation of mixed farming in the Middle Han River Valley, China by Xiujia Huan, Zhenhua Deng, Jinhui Xiang and Houyuan Lu in The Holocene

Supplemental Material

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Supplemental material, sj-xlsx-2-hol-10.1177_09596836221101253 for New evidence supports the continuous development of rice cultivation and early formation of mixed farming in the Middle Han River Valley, China by Xiujia Huan, Zhenhua Deng, Jinhui Xiang and Houyuan Lu in The Holocene

Footnotes

Acknowledgements

We would like to thank Dr. Jianping Zhang and Dr. Yong Ge for their help with the identification of millet phytoliths, and Dr. Hsiao-chun Hung and Dr. Mike T. Carson for language polishing of the manuscript.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the National Natural Science Foundation of China (Grant Nos. 41872027, 41907372, 41830322), the National Key Research and Development Program (Grant No. 2020YFC1521606), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB26000000).

ORCID iDs

Xiujia Huan

Zhenhua Deng

Supplemental material

Supplemental material for this article is available online.

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