Human-land relationship in the construction of historical settlements based on Complex Adaptive System (CAS) theory: evidence from Shawan in Guangfu region, China

Abstract

The relationship between humans and land environment within historical settlements reflects the intricate interplay between human societies, their construction activities, and the specific geographical contexts. Inadequate research into this relationship hinders a comprehensive understanding of the social spatial intricacies inherent in historical settlements. This paper adopts the theoretical framework of complex adaptive system and takes Shawan Ancient Town in Guangfu area of China as an example. Under the geographical background of sustainable land growth in the coastal zone, this study analyzed the subtle changes in the relationship between people and land during the historical construction, and the key findings of the investigation are threefold: (1) Land resources play a central role in the construction of human-land relationships in historical settlements. The geographical environment and social institutions serve as configuring factors in the formation and evolution of human-land relationships. These factors collectively determine the formation and evolution of human-land relationships. (2) Social space emerges as a pivotal manifestation of the human–environment relationship in historical settlements, transcending mere physical dimensions. Consequently, a holistic study of this relationship necessitates a comprehensive exploration not only of spatial configurations but also of the intricate interconnections among social bonds, structural formations, societal order, and settlement spatiality. (3) Drawing on the framework of complex adaptive systems theory, the study disentangles intricate elements within the human-land relationship of historical settlements. It distills and examines the manifestations of four intricate adaptive capacities—namely aggregation, non-linearity, flow, and diversity—alongside the mechanisms of tags, internal models, and fundamental building blocks. It is believed that the study of historical settlements in coastal areas needs to grasp the invariable social-spatial objects such as geographical environment, land form, local beliefs. Take it as a clue to sort out how other elements of change have iterated and transformed in the process of historical evolution, such as the rise and fall of families, land ownership changes and social class evolution. This paper explores the value connotation of historical settlements from the perspective of dialectic thinking of change and invariance with CAS theory, which has theoretical significance for protection of settlement's human-land relationship from the perspective of "social-spatial".

Introduction

Research object

Historical settlements represent a comprehensive term encompassing the diverse array of human habitation forms throughout history, reflecting deliberate human endeavors to exploit and modify the natural environment to establish viable living environments [1, 2]. They can be broadly classified based on their geographical location into urban historical settlements (e.g., Siena and Bellagio in Italy, Isfahan in Iran, Dubrovnik in Croatia) and rural historical settlements (e.g., Ait Benhaddou in Morocco, ancient villages in southern Anhui, China).

The formation of historical settlements typically involves two primary processes: site selection and construction, representing the key human-land interactions [3]. Variegated trajectories of historical settlement emergence, characterized by distinct modalities of site selection, settlement establishment, and structured settlement construction, engender the manifold typologies observable in historical settlements [4]. Early inhabitants, discerning opportune natural conditions and evading hazards, judiciously selected settlement locales, thereby anchoring themselves in propitious environments. Subsequent to the establishment of settlements, corresponding land utilization and economic paradigms ensued, engendering the concomitant material space and social networks [5].

Martin Heidegger delved into the discourse on the correlation between settlement and construction, positing that the inherent existence of space is contingent upon its spatial relations. He contended that "settlement" constitutes the foundational locus of existence, contingent upon the comprehensive grasp of natural principles, land resources, societal convictions, and communal membership [6]. In this context, "construction" emerges as the integrative process that interconnects these four elements, facilitating their application in the practical endeavor of constructing settlement spaces [7].

If site selection is considered a manifestation of human-land interactions rooted in environmental dynamics, then construction emerges as a fundamental social practice. Amos Rapoport, an American architectural anthropologist, extensively explores the societal dynamics underlying settlement construction in his seminal work "House Form and Culture," a text whose enduring influence pervades contemporary scholarship [8]. Rapoport meticulously analyzes the characteristics and origins of residential typologies across diverse cultural contexts drawing upon the interdisciplinary perspectives of anthropology and cultural geography, "House Form" refers to the spatial form of settlements that corresponds to social and cultural structures, closely intertwined with local architectural styles and vernacular construction practices [9].

Human-land relationships can be observed in numerous historical settlements worldwide. Examining traditional rural settlements in China as a case study, the centripetal settlement pattern, with ancestral halls serving as central nodes, exemplifies the influence of kinship clustering and hierarchical arrangements [10]. Spatial morphology is shaped by social structures, which can be found in that case. With a slight difference are the Hottentot settlements in Namibia and South Africa, leadership rather than familial ties assumes prominence as the locus of power, and settlement morphology revolves around the dwelling of the leader consequently. Leader's residence is positioned where the sun rises on the day of settlement construction, while subordinate dwellings align along the trajectory of the sun's movement throughout the day, reflecting hierarchical social stratification. This arrangement even facilitates the inference of the specific timing of settlement establishment.

As productivity advances and societal histories unfold, the evolution of settlements often transcends rudimentary notions of mere habitation [11, 12]. Community emerges as an intricate product of human-land interactions as a result. Specifically speaking, aggregation behavior and communal lifestyles inherent in settlements give rise to the collective ethos of settlement societies, wherein ethnicity, ideologies, beliefs, social standing, and identity serve as cohesive elements [13, 14]. This phenomenon finds resonance in "Exploring Settlements" by Japanese architect Akira Fujii. Informed by settlement sociology, Fujii posits the existence of an underlying, indeterminate force propelling settlements towards communal cohesion, a foundational prerequisite for community formation [15].

Institutionalized structures, belief systems, kinship ties, and other intangible realms, undergo a process of materialization within the physical milieu of settlements. Shared values, perspectives on life and death, and senses of solidarity become deeply embedded in the consciousness of each collective member during this process [16]. Social communities emerge as a result, which not only serve to deter external invasion but also mitigate internal fissures, to safeguard the integrity and stability of historical settlements over a long period.

As a representation of the human-land relationship, site selection and construction activities reflect the interdependence between inhabitants and their natural surroundings. Human beings have always demonstrated subjective agency and can actively understand, utilize, and change the geographical environment [17]. Conversely, land is the material basis and space carrier for human survival, and the geographical environment restricts social and economic activities.

Therefore, the site selection and construction of historical settlements can be emblematically represented through the prism of human-land relations. These relations also serve as the core underlying the formation, development, and evolution of historical settlements. In a holistic sense, the relationship between man and the land transcends the limits of the natural sciences in the fields of environment [18], ecology [19], and geography [20]. Interventions in the humanities and social sciences, such as sociology [21], anthropology [22], history [23], cultural studies [24], and heritage science [25], will provide interdisciplinary perspectives.

Literature review

Research rooted in the framework of human-land relations has been directed towards elucidating the environmental characteristics of historical settlements [26]. Notably, analyses have scrutinized diverse modalities of land utilization, encompassing terraced agriculture (fields of strip-shaped terraces or wave-shaped sections built along a contour line on a hillside), polder (low-lying paddy fields surrounded with dikes), mound field cultivation (fields that rises more than 1 m above the water level by placing piles of wood in lake and marsh areas and then piling soil on top of them), and platform-based agrarian practices (fields where soil is piled into a platform for cultivation).On this basis, the relationship between historical settlement form and land use mode is further studied.

For instance, the Hani ethnic group residing in the mountainous regions of Yunnan Province, China, has historically inhabited elevations ranging from 800 to 1800 m above sea level. Employing astute land management, local inhabitants have engineered hillslopes into terraced agricultural landscapes, thus engendering historical settlements emblematic of terraced agriculture. These Hani terraced settlements serve as tangible embodiments of sophisticated agro-ecological systems, offering invaluable insights into the nuanced dynamics of human-land interactions [27]. Consequently, in 2013, they were inscribed onto the prestigious UNESCO World Cultural Heritage List.

Likewise, the Beemster polders, dating back to the early seventeenth century in the Netherlands, represent a seminal endeavor in coastal reclamation. Characterized by an intricate network of rectilinear land parcels, these polders symbolize an aspirational paradigm of symbiotic human-land relations. Correspondingly, the concomitant polder settlements retain their pristine and meticulously organized landscapes, showcasing a harmonious amalgamation of agricultural, hydraulic, and residential components. All of them exemplify the enduring cultural significance of human interventions in shaping and adapting to the natural environment [28], thus meriting their recognition as a UNESCO World Cultural Heritage Site.

The spatial configuration of settlements above land use patterns is considered to be the three-dimensional manifestation of human-land relations. In plain regions, for instance, where the topography imposes minimal constraints, populations tend to aggregate, resulting in grid-like settlement spatial patterns. Mountainous and hilly settlements have evolved cluster formations in contrast that adapt opportunistically to local conditions, with buildings arranged freely along roads. This phenomenon parallels the settlements observed in basin environments, where the intricate interplay of complex geographic terrain, climatic factors, and water and soil resources serves as the foundation, shaping the distinct morphological characteristics of basin settlements [29, 30].

Drawing from the example of the Tarim Basin in Xinjiang, China, settlements exhibit a propensity to locate near water sources, with few situated within the basin's flat expanse. Instead, they predominantly occupy the foothills surrounding the basin, where access to glacier meltwater is facilitated. Water systems play a central role in the construction of human-land relations across many historical settlements, with rivers/canals/lakes/ponds serving as abundant water sources and the surroundings of rivers offering fertile soil conducive to agriculture [31]. Guided by the influence of aquatic environments, the human-land systems of historical settlements undergo sustained development.

In addition to being a methodological perspective within historical settlement studies, the reconstruction of human-land relations is regarded as a research direction [32]. Settlements have evolved a stability rooted in human-land relations across historical epochs. Stability, in settlements, has perpetuated the spatial organization and societal order therein, serving as a fundamental driver in their enduring development. As of today, the human-land relations within historical settlements have become increasingly intricate, characterized by prominent regional and dynamic features. The processes, patterns, and holistic effects of human-land relations are also undergoing profound transformations [33].

The research focus has shifted from examining geographical environments to exploring regional demographics, resources, and developmental coordination paradigms. Particularly with the continuous outward migration of indigenous peoples from historical settlements and the influx of merchants and entrepreneurs, the complexity of population, resources, and social relations in the settlement is more significant [34, 35]. Furthermore, Traditional landscapes, vernacular architecture, and built environments are being steadily eroded, resulting in disruptions and fluctuations in the entrenched human-land relations within historical settlements.

Existing studies have embarked on explorations into the contemporary construction of human-land relations in historical settlements against this backdrop. They focus on the capacity of resource environments within settlements, patterns of industrial and economic development, ecological resilience, socio-spatial structures, and relationship networks [36,37,38]. These studies bear the responsibility of exploring the key issues such as the coupling model and path of human-land relationship in historical settlements, and are forward-looking.

In general, research on human-land relations in historical settlements has unveiled current patterns of spatial distribution and morphological characteristics, while also exploring a vision oriented towards the reconstruction of human-land systems. They have provided ample experiences, thereby constructing and enhancing historical settlement geography with human-land relations as its core. It is crucial to recognize that historical settlements, as cultural spaces specific to particular periods and regions, possess corresponding historical evolutionary logics and mechanisms of evolution [39]. The historical process of how settlements are sited and constructed not only determines their current built environment characteristics but also guides future preservation directions. Therefore, we need to prioritize the study of human-land relations to highlight the significance of such built heritage [40].

Existing research, however, lacks attention to the evolutionary mechanisms of human-land relations in historical settlements. In particular, the logic-relating research on the early residents' development, distribution, and possession of land resources is insufficient. Compared to research on the processes and phase characteristics of spatio-temporal evolution, mechanism studies transcend mere representations in settlement forms. Mechanisms, embedded within the genetic coding of settlement human-land systems, represent the most stable existence. Therefore, it is necessary to make targeted supplements.

Drawing upon the framework of Complex Adaptive Systems(CAS) theory, this study seeks to elucidate the evolutionary mechanisms underlying human-land relations within historical settlements. Within the historical context of the formation and evolution of "Sha Tian"—a characteristic land development form in the Guangfu region of China, characterized by embankment construction for sandy fields, the study focuses on Shawan, an ancient town, as a case study. Specifically, the purpose of this paper is to analyze the evolutionary mechanisms of human-land relations in sandy field areas, as well as the historical logic behind land development and utilization.

This study will examine how human activities, natural changes, and social institutions interact with each other in the construction of Shawan settlements. The connotation of human-land relationship of historical settlements in coastal areas is also under study. The resolution of these two inquiries will ameliorate the deficiencies inherent in current research, providing a supplementary investigation into the evolutionary mechanisms governing human-land relations. Moreover, it will hold broader implications for the preservation of settlement heritages in coastal and low-lying regions worldwide, thereby offering substantive insights for scholarly discourse and practical applications alike.

Materials and methods

Study area

China's Guangfu region is centered around the Pearl River Delta and encompasses the western and northern parts of Guangdong Province, as well as the southeastern part of Guangxi Province [41]. Its administrative jurisdiction includes cities such as Guangzhou, Hong Kong, Macau, Foshan, Zhaoqing, Gaoming, Shunde, Dongguan, Zhongshan, Zhuhai, Jiangmen, Qingyuan, Yunfu, Zengcheng, Huadu, and others. Shawan, is situated within the Panyu District of Guangzhou, Guangdong Province, China from the perspective of administrative division, the east of Guangfu region (Fig. 1).

Fig. 1

China's Guangfu area (slash part) and the location of Shawan in Guangfu area

Geographically speaking, Shawan is located in the lower reaches of the Xi River within the Pearl River Basin, constituting a coastal area situated in the southern region of the Pearl River Delta [42]. Sandy field, the main form of agricultural production in the Pearl River Delta basin, is a land-use landscape gradually formed by the local ancestors in the process of adapting to the natural environment. It has played an irreplaceable social and economic value in regional history. Shawan lies precisely at the junction of the sandy field district and the non- sandy field district. It is precisely this "peripheral" status that gives rise to the "central" characteristics of Shawan [43]. This particular attribute engenders heightened complexity within its human-land relationship, particularly regarding the "land."

Furthermore, Shawan was established during the Southern Song Dynasty (1127—1279 A.D.), boasting a history of over 800 years. Five prominent clans of He, Li, Lin, Wang, and Zhao engaged in land development, acquisition, and competition, fostering intricate interrelations among diverse stakeholders, thereby imbuing the "human" aspect of the human-land relationship with complexity throughout this extensive historical trajectory [44]. The Selection of Shawan as a case study promises to unveil a rich and intriguing human-land system that will contributes to the exploration of the complex features of historical settlements in the Guangfu region, guided by the dynamics of human-land relationships.

Research methods

The theory of Complex Adaptive Systems (CAS), denoted as CAS was introduced by Professor John Holland of the United States in 1994, one of the founders of the Santa Fe Institute, a pioneer and prominent representative in complexity science. He posited that the driving force behind the evolution of systems fundamentally emanates from within the system itself, specifically through the interactions among micro-level entities, resulting in the emergence of macro-level complexity phenomena [45, 46]. This research perspective centers on the interactions among intrinsic elements of the system. The corresponding research methodology extends beyond the mere description of objective phenomena, placing a greater emphasis on revealing the causal factors contributing to the constitution of objective phenomena and the evolutionary processes they undergo [55].

CAS arises from the interactions and co-evolution of adaptive agents. John Holland, focusing on the pivotal concept of adaptive agents, introduced seven essential characteristics that should be present in a model of complex adaptive systems: aggregation, non-linearity, flow, diversity, tag, internal models, and building blocks (Fig. 2). The Top four among them are universal attributes of complex adaptive systems, playing critical roles in adaptation and evolution. The latter three pertain to mechanisms and concepts relevant to the interaction between individuals and their environment [47].

Fig. 2

Aggregation, non-linearity, flow, diversity, tag, internal models, and building blocks in CAS

CAS can effectively elucidate the complex characteristics inherent in the evolution and formation of human-land relationships in historical settlements. Aggregation, among these characteristics, is a primary mechanism for constructing models of complex adaptive systems [48]. Agents gradually cluster around certain markers, and smaller, lower-level entities combine in specific ways under the influence of particular markers, giving rise to larger, higher-level entities, whose entities further form organizations and groups, fostering various types of social relationships.

Historical settlement is a complex system. residents, families and, clans in historical settlements function as the agents, formed through clustering as groups. Land resources were particularly important in the early settlement process centered on agricultural production, and often served as a tag to bind and divide groups. The competition among clans for land resources generates diverse social relationships, which ultimately manifest spatially, shaping the socio-spatial patterns of historical settlements.

Relationships resulting from the aggregation of agents are not linear, simple, or straightforward causal chains. Instead, they are intricate relationships intertwined with various feedback loops and interactive influences. When adaptive agents receive an influx of flows (material, informational, resource, etc.), corresponding patterns to respond to these inputs would be chosen. It eventually solidifies into structures with specific functions, known as building blocks. The proactivity and adaptability of building blocks are the intrinsic sources of system complexit [49].

In the construction of historical settlements, experiences related to land resource development, ownership relationships, distribution forms, inheritance logic, and more need to be learned, improved, and passed down. Internal models as experiences allow settlements to maintain basic stability for a period, forming a fixed network of building blocks. It may expand or change as social relationships are organized, achieving a phase-specific dynamic equilibrium that sustains the basic stability of the spatial form, structure, and pattern of historical settlements.

The complex processes of agent aggregation and resource flow within the system give rise to the nonlinear characteristics of human-land relationships in historical settlements [50, 51]. Moreover, they further generate diversity within these relationships: behavioral diversity (including land reclamation, ownership, distribution, inheritance, and hired labor) and agent diversity (including landowners, tenant farmers, hired laborers, etc.), which adds distinctions to the human-land relationships.

Confronted with the intricate and intertwined human-land relationships within historical settlements, CAS can offer an explanatory framework that elucidates how individuals within the settlement guide land development and how land, in turn, constrains people's construction activities.

Data collection

From May 2021 to August 2023, we conducted several anthropological field research, with an in-depth investigation into the historical culture, social identity, and collective consciousness in Shawan. The research involved consulting "Sha Wan Town Chronicle" and local historical materials and archives, where detailed records of major clans' lineages, acquired properties, and population data since their settlement were compiled. Furthermore, property includes the amount of land developed and occupied, as well as the income generated from leasing the land. The population data include the population size, family division, and kinship of each period since the Ming Dynasty. 15 semi-structured interviews and participatory observations were conducted with residents, and 82% of the interviewees were descendants of these families.

Results

Land use guided by geographic environment

During the Song Dynasty (960—1279A.D.), the gradual formation of the distributary delta occurred around the ancient bay in the Pearl River Delta region. The Xi River, Bei River, and Pearl River served as the headwaters, displaying a radial diversion pattern in the deltaic area. These three rivers, utilizing northwest-oriented faults and incised mouth bars, traversed mountainous terrain before forming radial distributary deltas beyond the mouth bars. River water surged through the terraced hills and ridges, discharging into the bay beyond this line. Sediment and organic matter carried by the rivers from upstream also began to accumulate on the backsides of these hills and terraces.

The formation of Sandy field in Shawan is evolving within such a geographical context. River water surges through the terraced hills and ridges, flowing into the bay and gradually shaping new shoals and sandbars. In the natural environment where the waters of the three rivers converge, Shawan begins to accumulate sand and emerge as land. In order to utilize the limited land for settlement and sustenance, early inhabitants of the Shawan region deposited stones on the shoals. They utilized the resistance of these stone foundations to block wind and waves, stabilize the riverbed, and accelerate sediment deposition. After repeated stacking of stones to form sandbars, embankments could be constructed. Around and within these sandbars, a grid of intersecting vegetation-covered hard mud was built to solidify the soil, prevent collapse, and gradually transform the muddy land into cultivable fields for agriculture.

As the coastline gradually recedes, sandy fields suitable for agriculture continue to form. Fields further away from the shallows are relatively termed as "mature lands", characterized by longer development time, better land quality, and higher yields. Based on the distance from the coastline and differences in terrain, sandy fields can be classified into three types: pit fields (irrigated by mountain springs), river fields (irrigated by river water), and enclosed fields (protected from tides and drained through embankments). Sandy fields closer to the tides are mostly tidal fields (lacking embankments, hence submerged during high tides), categorized as "raw lands", continually forming and awaiting development.

As an ever-expanding land resource, sandy fields continuously form through sedimentation at bayheads, along riverbanks, and further develop through human-made embankments. To some extent, the expansiveness of sandy fields serves as the foundation for the human-land relationship in the Shawan and broader Guangfu regions. The coastal location and mountainous terrain imply scarcity of available land resources, but the tidal movements in the marine environment facilitate land "creation". Over time, the Guangfu region has also transitioned from desolate and uninhabited areas to coastal settlements suitable for human habitation and agricultural activities.

Social structure guided by policy systems

The early migration driven by social mobility led to the exploitation and utilization of land, marking the inception of the evolutionary trajectory of human-land relationships in historical settlements. This narrative holds true for Shawan as well. During the Southern Song Dynasty (1127–1279 A.D.), incessant warfare in northern regions prompted a significant migration of populations from the Central Plains towards the south, crossing the Dayu Mountains to reach Guangzhou in hopes of settling and establishing livelihoods. These early migrants became the backbone of Shawan's population, concurrently facilitating substantial land reclamation and development in the broader Guangfu region.

Early migrants were predominantly from prominent clans. Taking Shawan as an example, during the late Southern Song Dynasty (1230–1279 A.D.), families of officialdom from five major clans—"He, Li, Lin, Wang, Zhao"—successively migrated to the Shawan region. Throughout the lengthy process of historical evolution, these clans emerged as power centers surpassing local governments. Among them, the progenitor of the He clan, He Deming, obtained uncultivated land in Shawan, becoming the first major clan to settle and thrive in the area. Subsequently, the other four clans migrated to Shawan through marriage alliances, thereby establishing legitimate settlement status (Fig. 3 Clan territory in early settlement construction).

Fig. 3

Clan territory in early settlement construction

With the increasing influx of migrants, a grassroots management system consisting of fixed household units was established, known as the "Li jia" system. In order to facilitate household registration and social control, the government anchored residents to the land, thus standardizing grassroots management systems within county-level rural areas. This grassroots organizational form, originating from the Ming Dynasty, assimilated migrant populations into local communities, stabilizing social order.

Apart from the clans, there were many refugees at the lower strata of society who were also registered during that period and subsequently settled in Shawan, around the year 1300 A.D. These refugees, displaced by conflict and lacking permanent abode, migrated to the Shawan region in search of sustenance. Through household registration, these refugees acquired formal status. At the time, the household registration system was largely intertwined with the military system. Concurrently with the integration of refugees into household registration, the Ming government also conscripted them into the military, organizing them to cultivate land in the Shawan area to meet military needs. The land cultivated by the military mainly comprised newly formed sandbars and terraces outside the Xi River and Bei River after the Song and Yuan dynasties, marking the initiation of large-scale reclamation of new sandy fields in the Shawan and Guangfu regions. It gradually evolved into a military settlement policy(Tuntian), furnishing abundant labor for the development of sandy fields in Shawan. Under the dominance of the "Lijia" and “Tuntian” system, the state apparatus intervened in the development process of sandy fields in Shawan.

As the scale of sandy fields continued to expand, clans, through land acquisition, resource monopolization, and local autonomy, formed a hereditary society centered around land ownership, capital, and discourse power. Since the Ming Dynasty, private land ownership in the Guangfu region has been formally recognized by the state. The five major clans continually expanded and occupied land within their respective areas to consolidate the power of their own ethnic groups. Due to the continuous formation of sandy fields and the corresponding surge in development and management tasks, there was a need for increased social labor participation. Against this backdrop, the five major clans began to utilize migrant populations as the primary labor force for the development of sandy fields, giving rise to a dual social structure of "clans-refugees". In this structure, clans as landowners possess both the ownership and usage rights of the land. They no longer engage in production activities but mostly hire refugees to develop land and engage in agricultural production, providing compensation in return. refugees create profits for the former and provide services while being controlled by them. This labor relationship has operated in Shawan for a long time, forming corresponding production orders and land use patterns, as well as the current settlement form (Fig. 4).

Fig. 4

Social structure Land development in Shawan

The complex connotations of human-land relationships in historical settlements

The historical settlement of Shawan has undergone several centuries of evolution, during which its human-land relationships have exhibited numerous complex characteristics. Against the backdrop of geographical environment and policy conditions, deconstructing the human-land relationships in the construction of historical settlements from the perspective of CAS theory will reveal rich and nuanced connotations.

Undeniably, aggregation is a necessary condition for the formation and evolution of settlements. Specific social contexts during certain periods drove population movements, including political struggles, warfare, famine, natural disasters, and major public health events, all of which influenced population mobility. If these historical events acted as propulsion for early residents' migration, then habitable land served as the attractive force for their settlement. Residents could gather and establish early settlements on inhabitable land. With the increase in settled population, residential and arable land continued to form, eventually developing into settlements of a certain scale.

This phenomenon is particularly pronounced in the land-scarce region of Shawan. Due to the scarcity of suitable residential land, the five major clans that migrated early had already occupied the best-positioned and most fertile land, concentrating their development on this basis. Limited land resources led to significant social aggregation. Different clans belonged to distinct social groups, with clear residential boundaries between them. Through the cultivation, farming, and leasing of sandy fields, they achieved the primitive accumulation of capital, leading to continuous growth and expansion of clan size. With the multiplication of descendants, social relations within the clans began to differentiate. For example, descendants of the Li clan in Shawan split into two branches, settling in the southwest and northeast regions respectively. Despite the spatial differentiation and dispersion of residential areas, the cohesive force of clan societies remained strong due to their collective belongingness. On the contrary, with internal differentiation and expansion, the more descendants there were, the more land they occupied, and the stronger their power became. The social differentiation within clans appears to be a separation of relationships, but beneath this surface lies a more potent accumulation of capital (Fig. 5).

Fig. 5

The social division within the clans

Land serves as both the certificate of capital and the foundational basis for human-land relationships. In the early construction process of Shawan as a historical settlement, sandy fields were crucial agricultural production resources. Different clans delineated their respective territorial rights over sandy fields through the development, control, and management of these lands, typically demarcating boundaries using boundary markers to signify land ownership. Besides sandy fields as productive land, signs distinguishing territorial boundaries also emerged in residential land, known as "li-fang." Residential land was divided into numerous "li-fang" units, with each clan occupying several such units. The boundaries between "li-fang" units were clear, serving to demarcate residential areas among different clans. Within each "li-fang," boundaries were delineated by gateways, with public streets outside and clan territory within. Entry through these gateways symbolized entry into the internal space of the clan. Additionally, within the concentrated residential areas of each clan, there were also ancestral hall buildings representing the clan's history (indicated by red markings in Fig. 3). These ancestral sites served as focal points for delineating the spiritual domain of each clan, forming the basis for mutual recognition among specific clan members or different clans. The boundaries and domains of human-land relationships were represented through spatial tags on the ground, such as boundary markers, gateways, and ancestral hall buildings.

Land circulation has become the most typical form of capital flow in historical settlements. The competition among the five major clans for the acquisition of development rights over sandy fields has established the primitive capital for clan development. The amount of sandy field development also determines the strength of the discourse power among the five major clans. Alongside the competition between clans, land resources also undergo circulation. Due to differences in clan economic strength, situations of mutual competition, suppression, and encroachment on residential land occur frequently. When the flow of capital is projected into the settlement space, changes in settlement patterns occur— the power scope, scale, and boundaries among different clans undergo changes, and even the ancestral hall buildings used for worship may vary in scale, specifications, and architectural styles, with the most powerful clans able to use the highest standards of configuration.

With the development of settlement society, the rate of capital, resource, population, and discourse flow has accelerated, resulting in a significant amount of uncertainty. This phenomenon exists both in the initial site selection and the later construction process of settlements. Uncertainty fosters the diversity of human-land relationships, leading to rich and diverse connotations of human-land relationships in historical settlements. Taking Sha Wan as an example, various utilization methods of sandy fields have been formed based on their distance from the coastline. The development of sandy fields has also resulted in diverse social structures such as clan-migrant, employer-employee, and core-periphery. This holds true for other historical settlements as well. The formation of human–environment relationships in historical settlements is inherently a lengthy process. In this process, numerous historical phenomena emerge that are unpredictable, unrepeatable, and even difficult to simulate, endowing the development and evolution of settlements with nonlinear characteristics. It is precisely because of this that historical settlements are endowed with a richer cultural connotation.

Through adaptive learning, human-land relationship in historical settlements can develop stably. The corresponding experiential learning solidifies into specific behavioral patterns within the human-land relationship. For example, regulations formed by settlement residents regarding land development and utilization, as well as the local autonomy and management codes established within the five clans, exemplify this. The experiences gained through adaptive learning, the rules formed, and the patterns discovered become the internal models and building blocks. As mechanisms that control the behavior and operational principles among entities within settlements, internal models and building blocks solidify the most important human-land relationships in the historical settlement construction process. This includes policies on land management, distribution, and inheritance; the production system formed by clans and migrants around land development and production; and the self-organizing systems established in historical settlements in the Guangfu region, operating in a political environment distant from central authority.

Discussion

The human-land relationship in historical settlements has always been in a state of evolution. For example, phenomena such as the differentiation of social structure, changes in social relations, and the solidification and disintegration of social strata have occurred over extended periods of development, albeit often imperceptibly. The intervention of the theory of complex adaptive systems has provided an explanation for the laws of change in human-land relationships in historical settlements. Based on four phenomena and three mechanisms, it offers a new perspective for analyzing the evolutionary characteristics of such relationships. This perspective has sparked related discussions, which can be summarized as follows:

The dominant role of land resources in the evolution of historical settlements' human-land relationships

During the early stages of settlement, the primary challenge faced by the first immigrants was to select suitable settlement locations and agricultural land for cultivation [52]. Subsequently, due to limitations in land resources and population growth, settlement populations reached saturation points, prompting them to continuously explore the capacity and quality of surrounding land resources. Shawan is a typical example in this regard. In the construction of Guangfu settlements, where land was relatively scarce, land resources have always played a leading role. They sought additional development space through methods such as land reclamation, land leveling, and expansion into hilly areas. Even today, the foundational role of land in the construction and development of historical settlements remains evident [53]. The value and significance of land resources, as well as the forms of land ownership, distribution, production, and reproduction, are perennial topics that cannot be avoided in the study of the evolution and logic of settlement development.

The formation and evolution of human-land relationships in historical settlements are fundamentally influenced by the geographic environment

The geographic environment constitutes the natural attributes of a region, including factors such as topography, climate, water resources, and soil quality, which determine the distribution and availability of various resources. It is particularly prominent in the early stages of settlement construction and also manifests to varying degrees in the middle and later stages of settlement development [54]. The fundamental reason for the formation and evolution of human-land relationships in historical settlements lies in the shaping role of the geographic environment. Historical settlements that evolve under different geographic environments exhibit fundamentally different characteristics. For example, river plains with fertile soil, flat terrain, and abundant water resources are suitable for agricultural development [55]. Therefore, agricultural settlements may be established in these areas for grain cultivation and production (such as ancient settlements along the Nile River in Egypt, historical settlements on the plains of the Indus River in India, and settlements on the plains of the middle and lower reaches of the Yellow River in China). Vast open grassland areas are conducive to animal husbandry, giving rise to nomadic settlements that migrate seasonally (such as settlements on the Karakum grasslands in Kazakhstan and in the Altai Mountains region of Xinjiang, China). Although historical settlements in different regions take on different forms, the geographic environment consistently shapes human life and activities. It plays a crucial role in the formation and evolution of human societies, local settlements, and their material foundations.

The policy systems of specific periods drive the evolution of human-land relationships

The push and pull of policy institutions stimulate social mobility and also influence the forms of social production and labor, to some extent serving as key mechanisms in the evolution of human-land relationships. Factors such as aggregation, nonlinearity, flow, and diversity in complex adaptive systems are closely related to the specific policy institutions of different periods and are greatly influenced by them. The policy background and institutional forms anchor the mobile population, including but not limited to household registration control, military system, land ownership relations, institutional regulations related to land development, local autonomy, and social management, guiding the construction of human-land relationships in historical settlements. For other historical settlements, the state system and local policies also play crucial roles in the construction of human-land relationships, serving as driving mechanisms for the formation and evolution of regional human-land relationships [56, 57]. Therefore,it is necessary to adopt a macroscopic perspective on policy conditions and institutional backgrounds in studying human-land relationships in historical settlements. Against this backdrop, the logic of human-land relationship evolution in settlements can be analyzed further.

The morphology of social spaces are representations of the evolution of human-land relationships in settlements

The projection of human-land relationships onto the social spatial level can reveal the complexity of these relationships in historical settlements. As a complex interweaving of various cultures and social backgrounds within settlements, human-land relationships give rise to intricate social interactions. Entities such as families, tribes, and villages influence resource allocation and decision-making processes, potentially leading to social hierarchies and power struggles, thereby forming specific social organizations and power structures. Anchored in the land, historical settlements establish social relationships based on human-land relationships. The "collective identity" within these social relationships is projected onto specific spatial domains, giving rise to various concepts of "boundaries" and "settlement units." Often, when historical settlements evolve to a certain stage, the relationships within social spaces become evident. Serving as a reflection of human-land relationships, the morphology of social space implies the essential attributes of these relationships and represents the outcome of their evolution (Fig. 6).

Fig. 6

Evolution law of human-land relationship in historical settlements

Conclusions

The theory of complex adaptive systems has disaggregated the intricate aspects of human-land relationships within historical settlements. It delineates the manifestations of four complex adaptive capacities: aggregation, non-linearity, flow, and diversity, while extracting the mechanisms of three complex adaptive capacities: tags, internal models, and building blocks. On this basis, it identifies the continuity and changing factors of human-land relationships in historical settlements. Invariant elements influence and guide the changing ones, providing clues for the evolution of human-land relationships. It offers valuable explanatory tools for complex systems like historical settlements, enabling the decomposition and clarification of complex issues.

Given the unclear mechanisms underlying the evolution of human-land relationships in historical settlements, this study employs the theory of complex adaptive systems to investigate the historical development of the Shawan ancient town settlement in Guangfu. It focuses on analyzing the influence of geographical environment and social structure on the construction of settlement space. The study draws the following conclusions:

• (1) Land resources play a central role in the construction of human-land relationships in historical settlements. The geographical environment and social institutions serve as configuring factors in the formation and evolution of human-land relationships. These factors collectively determine the formation and evolution of human-land relationships.

• (2) Human-land relationships require value representation at the level of social space. The social morphology and spatial structure within settlements serve as the carriers of human-land relationships. Therefore, in studying human-land relationships in historical settlements, it is essential to not only focus on physical space but also delve into the connections between social relations, structures, order, and settlement space. By delving into the deep-seated connotations of these human-land relationships, we can reflect how these relationships transcend mere spatial forms of expression.

This study provides a sample for research on human-land relationships in historical settlements in coastal areas and low-lying countries through the analysis of Shawan Ancient Town in the Guangfu region of China. It offers a perspective on human-land relationships that goes beyond architectural environmental protection, anchoring human-land relationships in social space. This perspective aids in understanding and interpreting the value of historical settlements and provides insights for their preservation, renewal, and development.

For future research, it is important to recognize that the human-land settlement environments vary across different regions. Even within Guangfu settlements, the evolution of human-land environments in different villages and towns follows their own logic. However, the method of settlement construction centered around land remains consistent. Further research is needed to compare and analyze the human-land relationships in different towns and settlements in the Guangfu region, elucidating the significance of factors such as land and clan lineage in these relationships.