Deciphering Domestication: Unique Soybean Pods at Wangjinglou

Deciphering Domestication: Unique Soybean Pods at Wangjinglou | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Deciphering Domestication: Unique Soybean Pods at Wangjinglou Liya Tang, Jiaying Ju, Qian Wu, Xinyi Liu, Peiliang Liu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4571188/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The morphological attributes of soybean pods represent a fundamental criterion for distinguishing between domesticated and wild soybeans. Nevertheless, due to the infrequent preservation of pods in archaeological contexts, bean size remains a common method for identifying domesticated or wild soybean. This study undertook a comprehensive analysis of valued carbonized soybean remains, encompassing both beans and pods from the Wangjinglou site. Furthermore, this research serves as a pivotal reference for accurately identifying remains of the genus Glycine at the site. Radiocarbon dating has pinpointed the age of both kinds of soybean remains to approximately 1550 cal. BC. Through measurement and observation, it was determined that the small-bean group encased in the curled pods pertains to wild soybeans, in contrast the large-bean group aligns with domesticated soybeans. This suggests that the morphological variation between domesticated and wild soybeans in China transpired no later than 1550 cal. BC, signifying an advancement of approximately 170-400 years compared to prior studies. Biological sciences/Evolution/Archaeology Biological sciences/Plant sciences Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Soybean holds paramount significance in agriculture due to its versatile applications in food production, oil extraction, and animal feed. Genetic and molecular investigations have conclusively established that the wild soybean ( Glycine soja ) serves as the progenitor of its domestic counterpart, Glycine max 1 . Wild soybean is extensively distributed in East Asia, encompassing regions such as northern Japan, Korea, the Russian Far East, and China 2 . Dong et al. 3 have delved into the genetic diversity of wild soybeans in China through molecular approaches, revealing three primary genetic diversity centers within the country. These centers are situated in the northeastern region, the middle and lower reaches of the Yellow River, and the coastal areas. The abundance of wild soybean resources and genetic diversity in these specified regions played a pivotal role in facilitating the domestication and cultivation of soybeans by the ancient Chinese. Alternatively, some scholars have proposed that a specific large-seeded soybean variety may have originated in Japan, later disseminating to China, Korea, and other regions. The timing of soybean domestication has long captivated the interest of archaeologists. Currently, the enlargement of seed size stands as a prevalent criterion for differentiating domesticated soybeans from their wild counterparts in archaeological sites 45 6 . For instance, scholars have noted that during the Longshan period, soybean seeds exhibited a discernible increase in size. By the Shang and Zhou periods, soybeans had evolved into a significant component of agricultural production. 4 7 However, this method presents limitations when applied to discerning the early stages of domestication in soybeans. In considering the early domestication of soybeans, characterized by smaller sizes closer to wild soybeans and distinct from fully domesticated variants, Zhao et al. 6 assert that beyond size, attention should be directed towards the presence and luster of the carbonized soybean seed coat. Other scholars employ alternative methods to investigate the soybean domestication process. For instance, Hymowitz 7 utilized seed electrophoresis protein analysis in conjunction with ancient Chinese historical documents, proposing that the processing and utilization of cultivated soybeans by the Chinese people took place around 1700 BCE (end of the Xia Dynasty and early Shang Dynasty) 8 . Additionally, Zong et al. 9 conducted a study analyzing the oil content of soybean seeds excavated from the middle and lower reaches of the Yellow River in China using X-Ray Tomography. By comparing sizes, they concluded that soybean cultivation and domestication in this region occurred no later than 7500 years ago. The pod stands out as the most straightforward and fundamental criterion for establishing the domestication status of the leguminous crops. In South America, notably at prehistoric sites such as Coxcatlan Cave and Tamaulipas Cave, well-preserved dried pods and seeds of Phaseolus coccineus have frequently emerged 1011 , offering pivotal evidence for early agricultural investigations in Mexico. In contrast, the preservation challenges associated with pods are evident at the Yuanqiao site in Henan Province, China, where only pod fragments have been discovered thus far. Regrettably, there exists a notable gap in specific descriptions pertaining to these identified pod fragments 12 . Nevertheless, a significant breakthrough occurred at the Wangjinglou site, where a collection of both soybean seeds and pods were unearthed. The carbon-14 dating for soybeans traced their origins back to the Erlitou and Erligang Cultures, effectively addressing the scarcity of dating data for soybean remains in China. This study, therefore, not only fills a critical gap in the dating records but also proves invaluable for advancing research on the identification of the Glycine genus within archaeological contexts and providing valuable insights into the historical cultivation and domestication of soybeans in the region, contributing to our understanding of ancient agricultural practices and the evolutionary history of soybeans in China. Wangjinglou and the relevant sites Wangjinglou is a city site that was continuously used from the Erlitou Culture to the Erligang Culture. It is located in Xinzheng, south of Zhengzhou, Henan Province (Fig.1). This site is a large-scale city site dating back to the Xia and Shang Dynasties, covering an area of approximately 1.8 million square meters. The site's existence spans the Erlitou Culture period and the Erligang Culture period. The Wangjinglou city site may have been the capital of a regional state during the Erlitou period. In the Erligang Culture period, the Wangjinglou city site served as an important military stronghold in the southern part of Zhengzhou, playing an important role in connecting the regions of Huang River and Huai River 13 . Results Identification The plant remains from the Glycine genus uncovered at the Wangjinglou site distinctly fall into two categories: one characterized by larger beans and the other by smaller beans (Fig. 2). Upon measurement, the smaller beans exhibit dimensions of approximately 2.61-3.89 mm in length and 1.69-2.63 mm in width, as depicted in Figure 2. In contrast, the larger beans demonstrate dimensions of 4.45-5.61 mm in length and 2.71-3.58 mm in width, also illustrated in Figure 2. The smaller grains present an elliptical shape that is slightly flattened, accompanied by surface cracks. Some exhibit longitudinal swelling and cracking along the dorsal ridge, yet the seed coat generally remains intact, firmly adhered to the grain. The seed coat possesses a rough texture and does not exhibit a strong reflection under light exposure (Fig. 3, b). Notably, some smaller grains are still enclosed within pods, which display a distinctive curled shape. In contrast, the larger grains feature an elongated oval shape and appear plump. Through the carbonization process, these larger grains underwent slight expansion and deformation, resulting in the peeling off of a significant portion of the seed coat (Fig. 3, c). Presently, the Glycine genus encompasses various species, including G. max (domesticated soybeans), G. soja (wild soybeans), G. gracilis , and G. tabacina . G. gracilis . 44 predominantly grow in the northeastern region of China, while G. tabacina is primarily found in Taiwan and Fujian. In northern China, particularly in the middle and lower reaches of the Yellow River, G. max and G. soja stand out as the predominant species. Consequently, there are distinct differences in growth locations exist between G. max , G. soja , G. gracili , and G. tabacin. Considering the specific location of the unearthed plants of the genus Glycine from the Wangjinglou site, it is most likely that these plants belong to the categories of G. max and G. soja. Contemporary wild soybean seeds are characterized by smaller size, a black outer layer, and a rough texture (Fig. 3, d). In contrast, cultivated soybeans exhibit larger seeds with smooth texture (Fig. 3, e). In order to provide further confirmation regarding the species of the genus Glycine of the remains unearthed at the Wangjinglou site, this study implemented a charring experiment involving contemporary pods of the genus Glycine (Fig. 3, f. g.). The experiment incorporated two key indicators: heating temperature and thermal insulation time. Drawing inspiration from Zhao's previous carbonized experiments on soybeans 6 , the pods of both contemporary domesticated soybeans and wild soybeans underwent controlled combustion at 300°C, sustained for a duration of ten minutes. Subsequently, the specimens were observed after cooling to room temperature to evaluate the effects of the charring process. Through the observation of the morphology of contemporary pods of the genus Glycine , it was noted that the pods undergo a reduction in size and display a curled shape after the charring process. However, significant differences were observed in the charring characteristics of pods between wild soybeans and domesticated soybeans. The carbonization of wild soybean pods results in a more pronounced degree of curling and smaller size (Fig. 3, h), whereas the carbonization of domesticated ones leads to a less pronounced degree of curling and a larger size (Fig. 3, i). Upon examining the carbonized pods unearthed at the Wangjinglou site, their characteristics closely resemble the carbonized pods of contemporary wild soybeans. This similarity leads to the conclusion that the pods excavated at the site likely belong to wild soybeans. The distinctive charring patterns observed contribute valuable insights into the identification and differentiation of the remains of the genus Glycine at the archaeological site. In contrast to wild soybeans, the palisade cell layer of the seed pod in cultivated soybeans is thinner and loosely arranged, while the spongy parenchyma layer is thicker. This configuration enhances the water-absorbing capacity of cultivated soybeans, resulting in a soft and easily peelable seed coat. Moreover, cultivated soybeans boast a high oil content, making them highly flammable. When ignited, the cotyledons of soybeans expand and burst, creating uneven craters or cavities in the aftermath of combustion 25 . Carbon-14 dating results Ash pits H290 and H319, identified within the Erlitou Culture IV at the Wangjinglou site. Among them, H290 unearthed a considerable number of carbonized wild soybean grains and pods, while H319 revealed well-preserved carbonized soybean remains. Accelerator mass spectrometer (AMS) radiocarbon dates were obtained for soybeans and wild soybeans from Wangjinglou site to confirm the ages of the carbonized seeds (Table 2). Both wild soybeans and soybeans date from 1600 to 1400 BC, which is consistent with their respective contexts. Lab No Material Context Conventional Radiocarbon Date Calibrated Dates at 95.4% Beta -600463 Soybean H319 3300+/-30 BP 1623-1502 cal BC (3571-3451 cal B.P.) Beta -600464 Wild Soybean H290 3220+/-30 BP 1531-1427 cal BC (3481-3377 cal B.P.) Table 2. Radiocarbon dates （ AMC 14 C ） obtained for remains of the genus Glycine unearthed at the Wangjinglou site. Discussion Significance of wild soybean pods Until recently, archaeological sites rarely yielded wild soybean pods or soybean pods. 6 Fortunately, at the Wangjinglou site, we uncovered both soybean pods and the distinctive phenomenon of pod curling in wild soybeans (Fig. 3, a). This discovery closely resembles the morphology of contemporary carbonized wild soybean pods (Fig. 3, h), offering crucial evidence for identifying the species of the genus Glynine at the Wangjinglou site. In contemporary archaeological practice, distinguishing between soybeans and wild soybeans relies primarily on size and seed morphology. Notably, in botanical studies, seed morphology alone is not the predominant characteristic for discerning between domesticated and wild soybeans. Enlarged seed size, a trait indicative of domestication, typically emerges in later stages of the cultivation process 1 . Plant science places greater emphasis on features related to the overall plant and pods. Domesticated soybeans typically display a shrub-like growth pattern characterized by a thick main stem and sparse branches. In contrast, wild soybeans exhibit a creeping or climbing vine structure with a slender main stem and smaller branching stems. 20 Crucially, the structural composition of plant tissues, particularly the thick-walled fiber cells with layered cellulose along specific directions in the pod, serves as a key criterion. Armon's 45 analysis of pod cracking in leguminous plants highlighted those changes in cell water content result in anisotropic contraction, causing flat pods to reverse curl into spiral strips. The degree of pod curling varies with different pod widths. (Fig.3, h, i) Further distinctions lie in the seeds and pods of wild soybeans, which are characterized by smaller seeds and narrower pods. Additionally, their hard, non-glossy seed coat is challenging to peel, and they exhibit a more explosive pod opening compared to the cultivated soybeans 7 . Pod dehiscence, the natural splitting open of a plant’s fruit peel upon maturity, is a crucial phenomenon within the Fabaceae family 22 . This process plays a significant role in seed dispersal and is closely tied to crop yield. Kang 46 conducted an analysis of pod shattering rates in wild soybeans, landrace, and cultivated soybeans across China. The results indicated that wild soybeans consistently displayed a stable and relatively high pod dehiscence phenotype, contrasting with the lower pod dehiscence rates observed in landrace and cultivated soybeans. Although the phenomenon of pod splitting is still present in landrace and cultivated soybeans, pod morphology remains a vital factor for identifying leguminous plants unearthed in archaeological contexts. The pods of wild soybeans exhibit an instinctive behavior of cracking open and curling upon drying (Fig. 3, f). Genetic studies on both wild and cultivated soybeans have identified the influence of two key genes, SHAT1-5 and Pdh1, on pod dehiscence. Funatsuki 47 successfully cloned the primary regulatory gene for soybean pod dehiscence, Pdh1. This gene is notably highly expressed in the pod walls, promoting lignin deposition and causing distortion in the pod walls, ultimately leading to pod dehiscence. The establishment of soybean domestication in China Previous archaeobotanical studies have provided insights into the early utilization of wild soybeans at the Peiligang cultural site along the middle reaches of the Yellow River, dating back to 9000-7000 B.P. 4 . However, the process of domesticating wild soybeans was protracted. To gain a more nuanced understanding of this progression, we conducted a principal component analysis on the compensated measured values of domesticated soybeans unearthed at archaeological sites, where PC1 represents length, and PC2 represents width (Fig. 4). The conspicuous variations in length serve to illustrate the domestication process of early soybeans in the Central Plains region. Early data from the Wangchenggang site (2500-1800 BC) indicate substantial deviations in soybean characteristics compared to wild soybeans. However, the evolutionary trajectory is far from linear. During the period from 1850-1750 BC, soybean remains from the Xinzhai and Dongzhao sites exhibit smaller dimensions compared to those from Wangchenggang, with some even resembling the size of contemporary wild soybeans. Notably, certain data falls between the characteristics of ancient domesticated soybeans and wild soybeans. Consequently, scholars have theorized that the transition from the Longshan culture to the Xinzhai period represents a pivotal phase in soybean domestication, shaped by human factors or regional environmental variations. Moving into the Erilitou culture (1735-1530 BC), as evidenced by sites such as Wangjinglou, Erlitou, and Huadizui, the morphology of domesticated soybeans gradually stabilizes, and the contrast in size from wild soybeans becomes more pronounced. In a prior study focusing on Shang Dynasty soybeans at the Daxinzhuang site in Shandong, scholars argued that post-Shang Dynasty cultivated soybeans exhibited distinct differences from wild soybeans in morphology, oil content, and protein content 9 . Notably, at the Daxinzhuang site, a clear differentiation between large-grain and small-grain groups is evident, with radiocarbon dating[1] placing the large-grain group between 3179-2994 cal B.P. and 3348–3165 cal B.P. 9 However, at the Wangjinglou site, cultivated soybean remains are dated to 3571-3451 cal B.P., while wild soybean remains date back to3481-3377 cal B.P. The medians of these dates precede those of bean grains at the Daxinzhuang site by 170-400 years. Furthermore, the Wangjinglou site contains wild soybean seed remains and corresponding pod remnants with distinct morphologies from cultivated soybeans, suggesting that the establishment of soybean domestication in the Yellow River Basin occurred much earlier than previously predicted. The role of wild soybean The carbonation process is a highly intricate phenomenon, typically resulting from deoxygenation and dehydration reactions induced by elevated temperatures. This process transforms organic substances into inorganic carbonized materials, recoverable through flotation. 48 Among the 280 carbonized wild soybean remains, 272 are concentrated at the bottom of H290. It is noteworthy that people of that era clearly distinguished the various uses of wild soybeans and cultivated soybeans. Cultivated soybeans, as one of the ancient "Five Grains" in China, serve not only as a primary source of edible oil but also hold significant medicinal value. Various ancient texts, such as Zhou Li 49 and Fifty-Two Prescriptions 50 , repeatedly mention the medicinal value of soybeans and their leaves. In traditional Chinese medicine research, wild soybeans are also considered to have important medicinal value 51 . Additionally, wild soybeans, as non-crops, they can be intercropped with other crops to improve soil fertility and enhance crop production 52 . Determining the medicinal value of wild soybeans is challenging due to a lack of direct archaeological evidence. Two possible roles of the ancient wild soybeans of H290 could be analyzed. One role is as a cushion for some kind of architecture. The bottom comprises loose and porous soil containing a significant amount of black straw ash. The relatively regular and symmetrical shape of the pit suggests that its original function was a designated pit (Fig. 5, a), and these wild soybean plants might have been intentionally gathered at the bottom, closely associated with the pit's original function. The other role of wild soybeans could be as a type of feed discarded into this pit. The plant remains at the bottom of H290 consist predominantly of leguminous and Poaceae plants (Fig. 5, b), with Poaceae plants dominated by Digitaria sanguinalis and millet. D. sanguinalis , a fast-growing grass of the Poaceae family, is a high-nutrient, palatable weed, excellent as feed for livestock. Millet, with high yield and easy cultivation, serves as both a grain crop and a fodder crop. Green millet plants can be used as green forage or turned into hay. Due to their high protein content, both the seeds and plants can serve as feed. Therefore, the ancient wild soybeans might have likely been used as livestock feed. 53 [1] To facilitate comparison, the dating results of the Daxinzhuang site have been recalibrated using the IntCal20 curve. Conclusion The Wangjinglou site has yielded a significant trove of carbonized wild soybean pods. This article, consolidating data on soybean morphology from diverse sites (Wangjinglou, Huadizui, Dongzhao, Huizui, Erlitou) and incorporating radiocarbon dating of soybean remains from the Wangjinglou site, unveils a crucial revelation—the distinct differentiation between cultivated and wild soybeans in China emerged no later than 1550 BC, surpassing previous estimates by approximately 170-340 years. The simultaneous discovery of carbonized wild soybean pods and wild soybean grains at the Wangjinglou site establishes a benchmark for identifying soybean plants unearthed from archaeological sites in the future. Traditionally, studies on soybean domestication relied on indicators such as seed size and oil content to infer the domestication process. However, the morphology of pods stands out as the most direct evidence for distinguishing cultivated soybeans from their wild counterparts. In archaeological contexts, the preservation of carbonized pods poses challenges, and depending solely on soybean morphology studies may not guarantee an objective and accurate identification of early soybean remains. Additionally, this article delves into the utilization of wild soybeans during the Erlitou period. 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Study on the Research Progress of Sojae Semen Nigrum. Asia-Pacific Traditional Medicine 13, (2017). Zhou, F., Chen, S. & Li, Y. Study on the Feeding Value of Wild Soybean in Hefei. Journal of Anhui Agricultural Sciences 42, (2014). Zhou, F., Chen, S. & Li, Y. Study on the Feeding Value of Wild Soybean in Hefei. Journal of Anhui Agricultural Sciences 42, (2014). Additional Declarations No competing interests reported. Supplementary Files Supplementarymaterial.pdf Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4571188","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":323553216,"identity":"cd653c12-2f1a-48b6-8fa6-c44f9aaaf224","order_by":0,"name":"Liya Tang","email":"","orcid":"","institution":"Northwest University","correspondingAuthor":false,"prefix":"","firstName":"Liya","middleName":"","lastName":"Tang","suffix":""},{"id":323553217,"identity":"b85acc29-734a-415a-b8a7-ac6b1354171f","order_by":1,"name":"Jiaying Ju","email":"","orcid":"","institution":"University of Bologna","correspondingAuthor":false,"prefix":"","firstName":"Jiaying","middleName":"","lastName":"Ju","suffix":""},{"id":323553218,"identity":"40dafdc4-a5f4-4c6a-8c3d-1b606e2b256b","order_by":2,"name":"Qian Wu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIiWNgGAWjYDACZjiLh/EBkJRhYGAjXguzAQODAQ9hLQjAwyZBlBa+48zPHjC2Mcibt589VvGx7Q8PP3tbAsOPim04tUgeZjM3AGoxnHMmL+3mzDYDHsmeYwcYe87cxqnF4DCDmQTjNgbGGRI8Zrd5gVoMbqQ3MDO24dPC/g2kxR6kpZhILTxgWxJBWpghWtIO4NUieZinTCLxn0TyDJ4cY8kZ54xBfkk4iM8vfOePb5P4cMbGdgb7GcMPH8rk5IAhZvjgRwVuLQwHgDiBQQJTEL+WUTAKRsEoGAV4AQBvFEtBuMxvVgAAAABJRU5ErkJggg==","orcid":"","institution":"Zhengzhou Institute of Cultural Relics and Archaeology, Zhengzhou, China.","correspondingAuthor":true,"prefix":"","firstName":"Qian","middleName":"","lastName":"Wu","suffix":""},{"id":323553219,"identity":"90b45ecf-4950-41e9-b2c5-a188179107f9","order_by":3,"name":"Xinyi Liu","email":"","orcid":"","institution":"Washington University in St. Louis","correspondingAuthor":false,"prefix":"","firstName":"Xinyi","middleName":"","lastName":"Liu","suffix":""},{"id":323553220,"identity":"b50c32e5-34a9-45fb-82af-4e3fbc36fb61","order_by":4,"name":"Peiliang Liu","email":"","orcid":"","institution":"Northwest University","correspondingAuthor":false,"prefix":"","firstName":"Peiliang","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2024-06-12 15:06:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4571188/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4571188/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":60089555,"identity":"9a1729e8-f0d6-4761-9326-5e1ccc2a5039","added_by":"auto","created_at":"2024-07-11 15:43:08","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":909360,"visible":true,"origin":"","legend":"\u003cp\u003eThe archaeological records of soybean remain unearthed in northern China span from the Neolithic to the Bronze Age\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e1. Xinglonggou14 2. Erdaojingzi15 3. Sanzuodian16 4. Dingjiawa17 5. Zhaocun18 6. Shimao19 7. Shouguang20 8. Yulin21 9. Daxinzhuang9 10. Liujiazhuang22 11. Shilipu23 and Helou24 12. Jinqiao25 13. Yinxu17 14. Xiaoshuangqiao26 15. Chezhuang27 16. Dongzhao28 17. Guanzhuang29 18. Wangjinglou19 19. Xinzhai30 20. Wangchenggang31 21. Chengyao32 22. Huadizui33 23. Erlitou34 24. Dongyang35 25. Xinjie36 26. Yangguanzhai37 27. Gongbeiya38 28. Zaolinhetan39 29. Anban40 30. Zhouyuan41 31. Gouli42 32. Lajia43\u0026nbsp;\u003c/p\u003e","description":"","filename":"figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4571188/v1/34d73b844a83c4b8a5d46d28.jpg"},{"id":60088782,"identity":"b80cd521-1e7c-47d5-93c0-822e034ab1ee","added_by":"auto","created_at":"2024-07-11 15:35:08","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":314479,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA scatter plot depicting the sizes of soybean genus plants excavated from the Wangjinglou site (Compensated)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4571188/v1/0a87264f6801eacc1f585882.jpg"},{"id":60088786,"identity":"fba1e0f9-ac7a-402e-9872-b8f09d31a0a5","added_by":"auto","created_at":"2024-07-11 15:35:11","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":747529,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSoybean and wild soybean. \u003c/strong\u003e(a. unearthed \u003cem\u003eG.soja\u003c/em\u003e pod, b. unearthed \u003cem\u003eG.soja\u003c/em\u003e soybean，c. unearthed \u003cem\u003eG.max\u003c/em\u003e soybean, d. contemporary \u003cem\u003eG.soja\u003c/em\u003esoybean and e. contemporary\u003cem\u003e G.max \u003c/em\u003esoybean, f. contemporary \u003cem\u003eG.soja \u003c/em\u003epods, g. contemporary \u003cem\u003eG.max \u003c/em\u003epods, h. carbonized contemporary \u003cem\u003eG.soja\u003c/em\u003e pods, i. carbonized contemporary \u003cem\u003eG.max\u003c/em\u003epods.)\u003c/p\u003e","description":"","filename":"figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4571188/v1/24620854b708d60a5d35b566.jpg"},{"id":60088788,"identity":"5641890f-4e2c-4abe-8705-583599d63699","added_by":"auto","created_at":"2024-07-11 15:35:14","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":557878,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe principal component analysis of contemporary \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eG. max\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e, contemporary \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eG. soja \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003eand ancient domesticated soybeans from the Longshan to Erlitou periods in the Central Plains region.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4571188/v1/af27894e539712cf196b3b98.jpg"},{"id":60088785,"identity":"679e33d2-585f-4965-b127-d357b0b60f78","added_by":"auto","created_at":"2024-07-11 15:35:10","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":104395,"visible":true,"origin":"","legend":"\u003cp\u003eH290 vertical section diagram and unearthed plant assemblage. (a. the vertical section diagram, b. unearthed plant assemblage.)\u003c/p\u003e","description":"","filename":"figure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4571188/v1/447247a3a32def48261fcdef.jpg"},{"id":69486647,"identity":"ec408b74-1544-41fc-b8ca-4f710918044c","added_by":"auto","created_at":"2024-11-21 01:46:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3063996,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4571188/v1/350069d8-7fec-47e6-83c3-d0b68f903410.pdf"},{"id":60088790,"identity":"fa7b3731-8d16-4533-ac4d-db65ee5c6224","added_by":"auto","created_at":"2024-07-11 15:35:14","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":181682,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterial.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4571188/v1/aceb257eaf9b1f718ba90921.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Deciphering Domestication: Unique Soybean Pods at Wangjinglou","fulltext":[{"header":"Introduction ","content":"\u003cp\u003eSoybean holds paramount significance in agriculture due to its versatile applications in food production, oil extraction, and animal feed. Genetic and molecular investigations have conclusively established that the wild soybean (\u003cem\u003eGlycine soja\u003c/em\u003e) serves as the progenitor of its domestic counterpart, \u003cem\u003eGlycine max\u003csup\u003e1\u003c/sup\u003e.\u003c/em\u003e Wild soybean is extensively distributed in East Asia, encompassing regions such as northern Japan, Korea, the Russian Far East, and China\u003csup\u003e2\u003c/sup\u003e. Dong et al. \u003csup\u003e3\u003c/sup\u003e have delved into the genetic diversity of wild soybeans in China through molecular approaches, revealing three primary genetic diversity centers within the country. These centers are situated in the northeastern region, the middle and lower reaches of the Yellow River, and the coastal areas. The abundance of wild soybean resources and genetic diversity in these specified regions played a pivotal role in facilitating the domestication and cultivation of soybeans by the ancient Chinese. Alternatively, some scholars have proposed that a specific large-seeded soybean variety may have originated in Japan, later disseminating to China, Korea, and other regions.\u003c/p\u003e\n\u003cp\u003eThe timing of soybean domestication has long captivated the interest of archaeologists. Currently, the enlargement of seed size stands as a prevalent criterion for differentiating domesticated soybeans from their wild counterparts in archaeological sites\u003csup\u003e45\u003c/sup\u003e\u003csup\u003e6\u003c/sup\u003e. For instance, scholars have noted that during the Longshan period, soybean seeds exhibited a discernible increase in size. By the Shang and Zhou periods, soybeans had evolved into a significant component of agricultural production.\u0026nbsp;\u003csup\u003e4\u003c/sup\u003e\u003csup\u003e7\u003c/sup\u003eHowever, this method presents limitations when applied to discerning the early stages of domestication in soybeans.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn considering the early domestication of soybeans, characterized by smaller sizes closer to wild soybeans and distinct from fully domesticated variants, Zhao et al.\u0026nbsp;\u003csup\u003e6\u003c/sup\u003e assert that beyond size, attention should be directed towards the presence and luster of the carbonized soybean seed coat. Other scholars employ alternative methods to investigate the soybean domestication process. For instance, Hymowitz\u003csup\u003e7\u003c/sup\u003e utilized seed electrophoresis protein analysis in conjunction with ancient Chinese historical documents, proposing that the processing and utilization of cultivated soybeans by the Chinese people took place around 1700 BCE (end of the Xia Dynasty and early Shang Dynasty)\u003csup\u003e8\u003c/sup\u003e. Additionally, Zong et al. \u003csup\u003e9\u003c/sup\u003e conducted a study analyzing the oil content of soybean seeds excavated from the middle and lower reaches of the Yellow River in China using X-Ray Tomography. By comparing sizes, they concluded that soybean cultivation and domestication in this region occurred no later than 7500 years ago.\u003c/p\u003e\n\u003cp\u003eThe pod stands out as the most straightforward and fundamental criterion for establishing the domestication status of the leguminous crops. In South America, notably at prehistoric sites such as Coxcatlan Cave and Tamaulipas Cave, well-preserved dried pods and seeds of \u003cem\u003ePhaseolus coccineus\u003c/em\u003e have frequently emerged\u003csup\u003e1011\u003c/sup\u003e, offering pivotal evidence for early agricultural investigations in Mexico. In contrast, the preservation challenges associated with pods are evident at the Yuanqiao site in Henan Province, China, where only pod fragments have been discovered thus far. Regrettably, there exists a notable gap in specific descriptions pertaining to these identified pod fragments\u003csup\u003e12\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eNevertheless, a significant breakthrough occurred at the Wangjinglou site, where a collection of both soybean seeds and pods were unearthed. The carbon-14 dating for soybeans traced their origins back to the Erlitou and Erligang Cultures, effectively addressing the scarcity of dating data for soybean remains in China. This study, therefore, not only fills a critical gap in the dating records but also proves invaluable for advancing research on the identification of the \u003cem\u003eGlycine\u0026nbsp;\u003c/em\u003egenus within archaeological contexts and providing valuable insights into the historical cultivation and domestication of soybeans in the region, contributing to our understanding of ancient agricultural practices and the evolutionary history of soybeans in China.\u003c/p\u003e\n\u003ch3\u003eWangjinglou and the relevant sites\u003c/h3\u003e\n\u003cp\u003eWangjinglou is a city site that was continuously used from the Erlitou Culture to the Erligang Culture. It is located in Xinzheng, south of Zhengzhou, Henan Province (Fig.1). This site is a large-scale city site dating back to the Xia and Shang Dynasties, covering an area of approximately 1.8 million square meters. The site\u0026apos;s existence spans the Erlitou Culture period and the Erligang Culture period. The Wangjinglou city site may have been the capital of a regional state during the Erlitou period. In the Erligang Culture period, the Wangjinglou city site served as an important military stronghold in the southern part of Zhengzhou, playing an important role in connecting the regions of Huang River and Huai River\u003csup\u003e13\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eIdentification\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe plant remains from the \u003cem\u003eGlycine\u003c/em\u003e genus uncovered at the Wangjinglou site distinctly fall into two categories: one characterized by larger beans and the other by smaller beans (Fig. 2). Upon measurement, the smaller beans exhibit dimensions of approximately 2.61-3.89 mm in length and 1.69-2.63 mm in width, as depicted in Figure 2. In contrast, the larger beans demonstrate dimensions of 4.45-5.61 mm in length and 2.71-3.58 mm in width, also illustrated in Figure 2.\u003c/p\u003e\n\u003cp\u003eThe smaller grains present an elliptical shape that is slightly flattened, accompanied by surface cracks. Some exhibit longitudinal swelling and cracking along the dorsal ridge, yet the seed coat generally remains intact, firmly adhered to the grain. The seed coat possesses a rough texture and does not exhibit a strong reflection under light exposure (Fig. 3, b). Notably, some smaller grains are still enclosed within pods, which display a distinctive curled shape. In contrast, the larger grains feature an elongated oval shape and appear plump. Through the carbonization process, these larger grains underwent slight expansion and deformation, resulting in the peeling off of a significant portion of the seed coat (Fig. 3, c).\u003c/p\u003e\n\u003cp\u003ePresently, the \u003cem\u003eGlycine\u003c/em\u003e genus encompasses various species, including \u003cem\u003eG. max\u003c/em\u003e (domesticated soybeans), \u003cem\u003eG. soja\u003c/em\u003e (wild soybeans), \u003cem\u003eG. gracilis\u003c/em\u003e, and \u003cem\u003eG. tabacina\u003c/em\u003e. \u003cem\u003eG. gracilis\u003c/em\u003e. \u003csup\u003e44\u003c/sup\u003e predominantly grow in the northeastern region of China, while \u003cem\u003eG. tabacina\u0026nbsp;\u003c/em\u003eis primarily found in Taiwan and Fujian. In northern China, particularly in the middle and lower reaches of the Yellow River, \u003cem\u003eG. max\u003c/em\u003e and \u003cem\u003eG. soja\u003c/em\u003e stand out as the predominant species. Consequently, there are distinct differences in growth locations exist between \u003cem\u003eG. max\u003c/em\u003e, \u003cem\u003eG. soja\u003c/em\u003e, \u003cem\u003eG. gracili\u003c/em\u003e, and \u003cem\u003eG. tabacin.\u003c/em\u003e Considering the specific location of the unearthed plants of the genus \u003cem\u003eGlycine\u003c/em\u003e from the Wangjinglou site, it is most likely that these plants belong to the categories of \u003cem\u003eG. max\u003c/em\u003e and \u003cem\u003eG. soja.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eContemporary wild soybean seeds are characterized by smaller size, a black outer layer, and a rough texture (Fig. 3, d). In contrast, cultivated soybeans exhibit larger seeds with smooth texture (Fig. 3, e). In order to provide further confirmation regarding the species of the genus \u003cem\u003eGlycine\u003c/em\u003e of the remains unearthed at the Wangjinglou site, this study implemented a charring experiment involving contemporary pods of the genus\u003cem\u003e\u0026nbsp;Glycine\u0026nbsp;\u003c/em\u003e(Fig. 3, f. g.). The experiment incorporated two key indicators: heating temperature and thermal insulation time. Drawing inspiration from Zhao's previous carbonized experiments on soybeans\u003csup\u003e6\u003c/sup\u003e, the pods of both contemporary domesticated soybeans and wild soybeans underwent controlled combustion at 300°C, sustained for a duration of ten minutes. Subsequently, the specimens were observed after cooling to room temperature to evaluate the effects of the charring process.\u003c/p\u003e\n\u003cp\u003eThrough the observation of the morphology of contemporary pods of the genus\u003cem\u003e\u0026nbsp;Glycine\u003c/em\u003e , it was noted that the pods undergo a reduction in size and display a curled shape after the charring process. However, significant differences were observed in the charring characteristics of pods between wild soybeans and domesticated soybeans. The carbonization of wild soybean pods results in a more pronounced degree of curling and smaller size (Fig. 3, h), whereas the carbonization of domesticated ones leads to a less pronounced degree of curling and a larger size (Fig. 3, i).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eUpon examining the carbonized pods unearthed at the Wangjinglou site, their characteristics closely resemble the carbonized pods of contemporary wild soybeans. This similarity leads to the conclusion that the pods excavated at the site likely belong to wild soybeans. The distinctive charring patterns observed contribute valuable insights into the identification and differentiation of the remains of the genus \u003cem\u003eGlycine\u003c/em\u003e at the archaeological site.\u003c/p\u003e\n\u003cp\u003eIn contrast to wild soybeans, the palisade cell layer of the seed pod in cultivated soybeans is thinner and loosely arranged, while the spongy parenchyma layer is thicker. This configuration enhances the water-absorbing capacity of cultivated soybeans, resulting in a soft and easily peelable seed coat. Moreover, cultivated soybeans boast a high oil content, making them highly flammable. When ignited, the cotyledons of soybeans expand and burst, creating uneven craters or cavities in the aftermath of combustion\u003csup\u003e25\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCarbon-14 dating results\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAsh pits H290 and H319, identified within the Erlitou Culture IV at the Wangjinglou site. Among them, H290 unearthed a considerable number of carbonized wild soybean grains and pods, while H319 revealed well-preserved carbonized soybean remains.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccelerator mass spectrometer (AMS) radiocarbon dates were obtained for soybeans and wild soybeans from Wangjinglou site to confirm the ages of the carbonized seeds (Table 2). Both wild soybeans and soybeans date from 1600 to 1400 BC, which is consistent with their respective contexts.\u003c/p\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.027829313543599%\" valign=\"top\"\u003e\n \u003cp\u003eLab No\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.512059369202227%\" valign=\"top\"\u003e\n \u003cp\u003eMaterial\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.018552875695732%\" valign=\"top\"\u003e\n \u003cp\u003eContext\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.09647495361781%\" valign=\"top\"\u003e\n \u003cp\u003eConventional Radiocarbon Date\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.34508348794063%\" valign=\"top\"\u003e\n \u003cp\u003eCalibrated Dates at 95.4%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.027829313543599%\"\u003e\n \u003cp\u003eBeta -600463\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.512059369202227%\"\u003e\n \u003cp\u003eSoybean\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.018552875695732%\"\u003e\n \u003cp\u003eH319\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.09647495361781%\"\u003e\n \u003cp\u003e3300+/-30 BP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.34508348794063%\"\u003e\n \u003cp\u003e1623-1502 cal BC\u003c/p\u003e\n \u003cp\u003e(3571-3451\u0026nbsp;cal B.P.)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.027829313543599%\"\u003e\n \u003cp\u003eBeta -600464\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.512059369202227%\"\u003e\n \u003cp\u003eWild Soybean\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.018552875695732%\"\u003e\n \u003cp\u003eH290\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.09647495361781%\"\u003e\n \u003cp\u003e3220+/-30 BP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.34508348794063%\"\u003e\n \u003cp\u003e1531-1427 cal BC\u003c/p\u003e\n \u003cp\u003e(3481-3377 cal B.P.)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2. Radiocarbon dates\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e（\u003c/strong\u003e\u003cstrong\u003eAMC\u003csup\u003e14\u003c/sup\u003eC\u003c/strong\u003e\u003cstrong\u003e）\u003c/strong\u003e\u003cstrong\u003eobtained for remains of the genus \u003cem\u003eGlycine\u003c/em\u003e unearthed at the Wangjinglou site.\u003c/strong\u003e\u003c/p\u003e"},{"header":"Discussion ","content":"\u003cp\u003e\u003cstrong\u003eSignificance of wild soybean pods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eUntil recently, archaeological sites rarely yielded wild soybean pods or soybean pods.\u003csup\u003e6\u003c/sup\u003e Fortunately, at the Wangjinglou site, we uncovered both soybean pods and the distinctive phenomenon of pod curling in wild soybeans (Fig. 3, a). This discovery closely resembles the morphology of contemporary carbonized wild soybean pods (Fig. 3, h), offering crucial evidence for identifying the species of the genus \u003cem\u003eGlynine\u003c/em\u003e at the Wangjinglou site.\u003c/p\u003e\n\u003cp\u003eIn contemporary archaeological practice, distinguishing between soybeans and wild soybeans relies primarily on size and seed morphology. Notably, in botanical studies, seed morphology alone is not the predominant characteristic for discerning between domesticated and wild soybeans. Enlarged seed size, a trait indicative of domestication, typically emerges in later stages of the cultivation process\u003csup\u003e1\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003ePlant science places greater emphasis on features related to the overall plant and pods. Domesticated soybeans typically display a shrub-like growth pattern characterized by a thick main stem and sparse branches. In contrast, wild soybeans exhibit a creeping or climbing vine structure with a slender main stem and smaller branching stems.\u003csup\u003e20\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eCrucially, the structural composition of plant tissues, particularly the thick-walled fiber cells with layered cellulose along specific directions in the pod, serves as a key criterion. Armon's\u003csup\u003e45\u003c/sup\u003eanalysis of pod cracking in leguminous plants highlighted those changes in cell water content result in anisotropic contraction, causing flat pods to reverse curl into spiral strips. The degree of pod curling varies with different pod widths. (Fig.3, h, i)\u003c/p\u003e\n\u003cp\u003eFurther distinctions lie in the seeds and pods of wild soybeans, which are characterized by smaller seeds and narrower pods. Additionally, their hard, non-glossy seed coat is challenging to peel, and they exhibit a more explosive pod opening compared to the cultivated soybeans\u003csup\u003e7\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003ePod dehiscence, the natural splitting open of a plant’s fruit peel upon maturity, is a crucial phenomenon within the Fabaceae family\u003csup\u003e22\u003c/sup\u003e. This process plays a significant role in seed dispersal and is closely tied to crop yield. Kang\u003csup\u003e46\u003c/sup\u003e conducted an analysis of pod shattering rates in wild soybeans, landrace, and cultivated soybeans across China. The results indicated that wild soybeans consistently displayed a stable and relatively high pod dehiscence phenotype, contrasting with the lower pod dehiscence rates observed in landrace and cultivated soybeans. Although the phenomenon of pod splitting is still present in landrace and cultivated soybeans, pod morphology remains a vital factor for identifying leguminous plants unearthed in archaeological contexts.\u003c/p\u003e\n\u003cp\u003eThe pods of wild soybeans exhibit an instinctive behavior of cracking open and curling upon drying (Fig. 3, f). Genetic studies on both wild and cultivated soybeans have identified the influence of two key genes, SHAT1-5 and Pdh1, on pod dehiscence. Funatsuki\u003csup\u003e47\u003c/sup\u003e successfully cloned the primary regulatory gene for soybean pod dehiscence, Pdh1. This gene is notably highly expressed in the pod walls, promoting lignin deposition and causing distortion in the pod walls, ultimately leading to pod dehiscence.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe establishment of soybean domestication in China\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePrevious archaeobotanical studies have provided insights into the early utilization of wild soybeans at the Peiligang cultural site along the middle reaches of the Yellow River, dating back to 9000-7000 B.P.\u003csup\u003e4\u003c/sup\u003e. However, the process of domesticating wild soybeans was protracted. To gain a more nuanced understanding of this progression, we conducted a principal component analysis on the compensated measured values of domesticated soybeans unearthed at archaeological sites, where PC1 represents length, and PC2 represents width (Fig. 4).\u003c/p\u003e\n\u003cp\u003eThe conspicuous variations in length serve to illustrate the domestication process of early soybeans in the Central Plains region. Early data from the Wangchenggang site (2500-1800 BC) indicate substantial deviations in soybean characteristics compared to wild soybeans. However, the evolutionary trajectory is far from linear. During the period from 1850-1750 BC, soybean remains from the Xinzhai and Dongzhao sites exhibit smaller dimensions compared to those from Wangchenggang, with some even resembling the size of contemporary wild soybeans. Notably, certain data falls between the characteristics of ancient domesticated soybeans and wild soybeans. Consequently, scholars have theorized that the transition from the Longshan culture to the Xinzhai period represents a pivotal phase in soybean domestication, shaped by human factors or regional environmental variations. Moving into the Erilitou culture (1735-1530 BC), as evidenced by sites such as Wangjinglou, Erlitou, and Huadizui, the morphology of domesticated soybeans gradually stabilizes, and the contrast in size from wild soybeans becomes more pronounced.\u003c/p\u003e\n\u003cp\u003eIn a prior study focusing on Shang Dynasty soybeans at the Daxinzhuang site in Shandong, scholars argued that post-Shang Dynasty cultivated soybeans exhibited distinct differences from wild soybeans in morphology, oil content, and protein content\u003csup\u003e9\u003c/sup\u003e. Notably, at the Daxinzhuang site, a clear differentiation between large-grain and small-grain groups is evident, with radiocarbon dating[1] placing the large-grain group between 3179-2994 cal B.P. and 3348–3165 cal B.P.\u003csup\u003e9\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eHowever, at the Wangjinglou site, cultivated soybean remains are dated to 3571-3451 cal B.P., while wild soybean remains date back to3481-3377 cal B.P. The medians of these dates precede those of bean grains at the Daxinzhuang site by 170-400 years. Furthermore, the Wangjinglou site contains wild soybean seed remains and corresponding pod remnants with distinct morphologies from cultivated soybeans, suggesting that the establishment of soybean domestication in the Yellow River Basin occurred much earlier than previously predicted.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe role of wild soybean\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe carbonation process is a highly intricate phenomenon, typically resulting from deoxygenation and dehydration reactions induced by elevated temperatures. This process transforms organic substances into inorganic carbonized materials, recoverable through flotation.\u003csup\u003e48\u003c/sup\u003e Among the 280 carbonized wild soybean remains, 272 are concentrated at the bottom of H290. It is noteworthy that people of that era clearly distinguished the various uses of wild soybeans and cultivated soybeans.\u003c/p\u003e\n\u003cp\u003eCultivated soybeans, as one of the ancient \"Five Grains\" in China, serve not only as a primary source of edible oil but also hold significant medicinal value. Various ancient texts, such as\u003cem\u003e\u0026nbsp;Zhou Li\u003csup\u003e49\u003c/sup\u003e\u0026nbsp;\u003c/em\u003eand \u003cem\u003eFifty-Two Prescriptions\u003csup\u003e50\u003c/sup\u003e\u003c/em\u003e, repeatedly mention the medicinal value of soybeans and their leaves. In traditional Chinese medicine research, wild soybeans are also considered to have important medicinal value\u003csup\u003e51\u003c/sup\u003e. Additionally, wild soybeans, as non-crops, they can be intercropped with other crops to improve soil fertility and enhance crop production\u003csup\u003e52\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eDetermining the medicinal value of wild soybeans is challenging due to a lack of direct archaeological evidence. Two possible roles of the ancient wild soybeans of H290 could be analyzed. One role is as a cushion for some kind of architecture. The bottom comprises loose and porous soil containing a significant amount of black straw ash. The relatively regular and symmetrical shape of the pit suggests that its original function was a designated pit (Fig. 5, a), and these wild soybean plants might have been intentionally gathered at the bottom, closely associated with the pit's original function.\u003c/p\u003e\n\u003cp\u003eThe other role of wild soybeans could be as a type of feed discarded into this pit. The plant remains at the bottom of H290 consist predominantly of leguminous and Poaceae plants (Fig. 5, b), with Poaceae plants dominated by \u003cem\u003eDigitaria sanguinalis\u003c/em\u003e and millet. \u003cem\u003eD. sanguinalis\u003c/em\u003e, a fast-growing grass of the Poaceae family, is a high-nutrient, palatable weed, excellent as feed for livestock. Millet, with high yield and easy cultivation, serves as both a grain crop and a fodder crop. Green millet plants can be used as green forage or turned into hay. Due to their high protein content, both the seeds and plants can serve as feed. Therefore, the ancient wild soybeans might have likely been used as livestock feed.\u0026nbsp;\u003csup\u003e53\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cdiv id=\"ftn1\"\u003e\n \u003cp\u003e[1] To facilitate comparison, the dating results of the Daxinzhuang site have been recalibrated using the IntCal20 curve.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe Wangjinglou site has yielded a significant trove of carbonized wild soybean pods. This article, consolidating data on soybean morphology from diverse sites (Wangjinglou, Huadizui, Dongzhao, Huizui, Erlitou) and incorporating radiocarbon dating of soybean remains from the Wangjinglou site, unveils a crucial revelation—the distinct differentiation between cultivated and wild soybeans in China emerged no later than 1550 BC, surpassing previous estimates by approximately 170-340 years.\u003c/p\u003e\n\u003cp\u003eThe simultaneous discovery of carbonized wild soybean pods and wild soybean grains at the Wangjinglou site establishes a benchmark for identifying soybean plants unearthed from archaeological sites in the future. Traditionally, studies on soybean domestication relied on indicators such as seed size and oil content to infer the domestication process. However, the morphology of pods stands out as the most direct evidence for distinguishing cultivated soybeans from their wild counterparts. In archaeological contexts, the preservation of carbonized pods poses challenges, and depending solely on soybean morphology studies may not guarantee an objective and accurate identification of early soybean remains.\u003c/p\u003e\n\u003cp\u003eAdditionally, this article delves into the utilization of wild soybeans during the Erlitou period. Taking into account the urban characteristics of the Wangjinglou site, it is proposed that during the Erlitou period, there was a deliberate distinction in the utilization of cultivated and wild soybeans. Wild soybeans might have served as a form of cushion at the base of purposefully designed architecture or potentially acted as raw materials for green and coarse forage, employed in livestock feeding.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHymowitz, T. On the domestication of the soybean. Economic Botany 24, 408\u0026ndash;421 (1970).\u003c/li\u003e\n\u003cli\u003eYamaguchi, H. 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Journal of Anhui Agricultural Sciences 42, (2014).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4571188/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4571188/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The morphological attributes of soybean pods represent a fundamental criterion for distinguishing between domesticated and wild soybeans. Nevertheless, due to the infrequent preservation of pods in archaeological contexts, bean size remains a common method for identifying domesticated or wild soybean. This study undertook a comprehensive analysis of valued carbonized soybean remains, encompassing both beans and pods from the Wangjinglou site. Furthermore, this research serves as a pivotal reference for accurately identifying remains of the genus Glycine at the site. Radiocarbon dating has pinpointed the age of both kinds of soybean remains to approximately 1550 cal. BC. Through measurement and observation, it was determined that the small-bean group encased in the curled pods pertains to wild soybeans, in contrast the large-bean group aligns with domesticated soybeans. This suggests that the morphological variation between domesticated and wild soybeans in China transpired no later than 1550 cal. BC, signifying an advancement of approximately 170-400 years compared to prior studies.","manuscriptTitle":"Deciphering Domestication: Unique Soybean Pods at Wangjinglou","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-11 15:35:01","doi":"10.21203/rs.3.rs-4571188/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e59a3901-8c5f-4691-a2f9-82cf49f1bf53","owner":[],"postedDate":"July 11th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":34217536,"name":"Biological sciences/Evolution/Archaeology"},{"id":34217537,"name":"Biological sciences/Plant sciences"}],"tags":[],"updatedAt":"2024-11-21T01:38:38+00:00","versionOfRecord":[],"versionCreatedAt":"2024-07-11 15:35:01","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4571188","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4571188","identity":"rs-4571188","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}