Paleoparasitology of Joseon period mummies in South Korea

In South Korea, as in other East Asian countries, paleoparasitology has developed along 2 major lines of research. The first focuses on the analysis of soil samples collected from archaeological excavation sites, particularly from urban ruins and ancient toilets (Shin et al. Reference Shin, Shim, Kim, Oh, Lee, Jung, Lee, Chai and Seo2014, Reference Shin, Seo, Shim, Hong, Kim, Betsinger and SN2020; Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021). These studies were not designed to identify specific parasite infections in individuals. Instead, their primary aim was to examine the relationship between parasitic infections and environmental conditions in areas inhabited by Koreans prior to the 20th century – a perspective rooted largely in archaeology (Shin et al. Reference Shin, Seo, Shim, Hong, Kim, Betsinger and SN2020).

In contrast, numerous well-preserved mummies from the Joseon Dynasty (1392–1910 CE) have been discovered in South Korea. Because intact coprolites can often be recovered from their intestines, researchers have been able to identify the specific parasite species that infected these individuals and to estimate the broader prevalence of parasitic infections in Joseon society (Shin et al. Reference Shin, Shim, Kim, Oh, Lee, Jung, Lee, Chai and Seo2014). This constitutes a significant achievement for both archaeological science and medical parasitology, as it provides robust, direct evidence of helminth infections among premodern Koreans and contributes to more refined bioarchaeological reconstructions of East Asian history (Seo et al. Reference Seo, Hong, Reinhard Kim, Shin, Shin and Bianucci2021).

Both approaches – paleoparasitology of soil samples and of mummies – have been pursued in South Korea since the early 2000s. Although their objectives differ, the results of one approach often complement the other. For example, parasite eggs identified in the faeces of Joseon mummies provide direct evidence of which species were infecting people at the time. The excellent preservation of many mummies has allowed the detection of parasite eggs that are difficult to recover from soil samples. Indeed, parasitological examination of Joseon mummies’ faeces has proven to be almost as sensitive and specific as examinations conducted on modern patients (Seo et al. Reference Seo, Hong, Reinhard Kim, Shin, Shin and Bianucci2021).

The parasite types and infection rates identified in Joseon mummy coprolites offer valuable clues about what might be found in archaeological soil strata. The information obtained from the mummy provides a more stable basis for interpreting the information obtained from the soil at the less sensitive excavation site. In the case of parasite eggs identified in the soil at the excavation site, they often have a relatively damaged appearance, and the information on the parasite identified in the mummy is of considerable help in these cases.

Over the past 20 years, our team has analysed 24 Joseon mummies, and the results suggest that infection rates during the Joseon period provide important context for interpreting the national survey data of the 20th century (Seo et al. Reference Seo, Oh, Hong, Chai, Cha, Bang, Cha, Wi, Park and Shin2017, Reference Seo, Hong, Reinhard Kim, Shin, Shin and Bianucci2021). Paleoparasitological analysis of mummified faeces has played a vital role in illuminating past infection burdens (Seo et al. Reference Seo, Hong, Reinhard Kim, Shin, Shin and Bianucci2021). Compared with soil samples, studies of individual coprolites yield higher parasite detection rates and thus more accurate reflections of historical infection status. Expanding research beyond soil contexts to include such materials is a major strength of paleoparasitology.

In brief, as for Ascaris lumbricoides and Trichuris trichiura, the most common geoparasite species known to be detected in modern or archaeological specimens from Korea (Shin et al. Reference Shin, Seo, Shim, Hong, Kim, Betsinger and SN2020; Seo et al. Reference Seo, Hong, Reinhard Kim, Shin, Shin and Bianucci2021), the infection rates observed in Joseon mummies were 58.3% (14/24) and 83.3% (20/24) respectively. By comparison, the 1971 national survey conducted by the Korea Association of Health Promotion reported corresponding rates of 54.9% for A. lumbricoides and 65.4% for T. trichiura. These findings suggest that parasitic infection rates of A. lumbricoides and T. trichiura remained consistently high for centuries, until they declined rapidly during South Korea’s modernization and industrialization.

In addition to these soil-transmitted helminths, considerable infection rates of Clonorchis sinensis (25%) and Paragonimus westermani (33.3%) were also identified in Joseon mummies, underscoring the heavy parasitic burden of the era (Seo et al. Reference Seo, Oh, Hong, Chai, Cha, Bang, Cha, Wi, Park and Shin2017, Reference Seo, Hong, Reinhard Kim, Shin, Shin and Bianucci2021). It is clear that such specific data on the parasite infection rate of people in the Joseon Dynasty are almost impossible without parasitological studies of Korean mummies.

Parasitology at archaeological ruins in South Korea

It is well established in medical science that high population density correlates with elevated parasite infection rates. In many developing countries, crowded living conditions lead to severe soil contamination with parasite eggs, resulting in widespread infection (Schulz and Kroeger, Reference Schulz and Kroeger1992; Larsen, Reference Larsen1995; Uga et al. Reference Uga, Ono, Kataoka, Safriah, Tantular, Dachla and Ranuh1995; Barnes, Reference Barnes2005; Shin et al. Reference Shin, Seo, Shim, Hong, Kim, Betsinger and SN2020).

In East Asian history, numerous major cities with populations reaching several hundred thousand emerged during the 17th century (Kim et al. Reference Kim, Ki, Kim, Chai, Seo, Oh and Shin2014). These urban populations may have been particularly vulnerable to parasitic infection, especially because human faeces were widely used as fertilizer for vegetable cultivation in urban and peri-urban areas (Mitsumata, Reference Mitsumata2008; Shin et al. Reference Shin, Fujita and Hong2023). However, it is not immediately evident from historical texts alone whether East Asian urban centres were disproportionately affected.

For this reason, paleoparasitological research has focused heavily on soils from premodern cities, as evidence indicates that parasite infection rates in large urban centres prior to the advent of modern public health measures were extremely high (Fonzo et al. Reference Fonzo, Scott, Duffy, Betsinger and SN2020; Shin et al. Reference Shin, Seo, Shim, Hong, Kim, Betsinger and SN2020, Reference Shin, Fujita and Hong2023; Reinhard et al. Reference Reinhard, Fujita and Shin2021). In South Korea, archaeological excavations are conducted in a highly systematic and regulated manner, resulting in the publication of thousands of excavation reports each year (National Research Institute of Cultural Heritage, 2021). Urban sites – particularly those associated with densely populated historical cities – have therefore provided unique opportunities for paleoparasitological research.

One of the most important examples is Hanseong (modern-day Seoul), the capital of the Joseon Dynasty. By the 17th century, Hanseong had developed into a major metropolis with an estimated population of approximately 200,000. Archaeological excavations have revealed that much of the city’s original urban layout – including palaces, government offices, residential quarters and associated infrastructure – remains preserved beneath the modern cityscape (Kim et al. Reference Kim, Ki, Kim, Chai, Seo, Oh and Shin2014).

For many years, paleoparasitological research in Seoul was not possible due to limited excavation. However, since the 2000s, large-scale urban redevelopment projects have required archaeological surveys prior to construction, creating new opportunities for palaeoparasitologists to collect soil samples. Working closely with archaeologists, we obtained soil specimens from historically significant locations, including palace precincts, major streets, markets and alleyways (Kim et al. Reference Kim, Ki, Kim, Chai, Seo, Oh and Shin2014).

These examinations revealed abundant ancient parasite eggs, especially those of soil-transmitted helminths (Kim et al. Reference Kim, Ki, Kim, Chai, Seo, Oh and Shin2014). The large number of eggs recovered from Hanseong’s urban soils confirms the high prevalence of parasitic infections among Joseon-era populations. The presence of substantial quantities of Ascaris lumbricoides and Trichuris trichiura eggs reflects severe contamination with human faeces and provides strong indirect evidence of the heavy parasitic burden borne by past communities (Kim et al. Reference Kim, Ki, Kim, Chai, Seo, Oh and Shin2014).

Why, then, were soil-transmitted parasite infections so prevalent in East Asia? One major factor was the widespread use of night soil – human excrement – as fertilizer. From the 17th century onward, cities such as Hanseong in Korea and Edo, Kyoto, and Osaka in Japan expanded rapidly, struggling to secure sufficient food supplies. Recycling human waste as fertilizer provided an essential solution, simultaneously supporting agricultural productivity and facilitating waste disposal (Mitsumata, Reference Mitsumata2008; Kim et al. Reference Kim, Ki, Kim, Chai, Seo, Oh and Shin2014; Reinhard et al. Reference Reinhard, Fujita and Shin2021; Shin et al. Reference Shin, Fujita and Hong2023).

In Korea, this recycling practice directly facilitated parasite transmission, as helminth eggs present in human faeces contaminated vegetables grown in surrounding farmlands. In the Joseon period, the problem may have been exacerbated by the common consumption of raw vegetables (Kim et al. Reference Kim, Ki, Kim, Chai, Seo, Oh and Shin2014). While this recycling system was highly efficient for food production and waste management, it inadvertently promoted the spread of soil-transmitted helminths, leading to chronic parasitic infections. Only with the introduction of chemical fertilizers during modernization and industrialization did infection rates of Ascaris and Trichuris decline dramatically – a shift that explains the sharp reduction in parasite prevalence after the 1970s (Kim et al. Reference Kim, Ki, Kim, Chai, Seo, Oh and Shin2014; Seo et al. Reference Seo, Oh, Hong, Chai, Cha, Bang, Cha, Wi, Park and Shin2017).

Historical texts raise an additional possibility for the widespread distribution of parasite eggs in urban soils. Sanitation in premodern Korean cities relied heavily on seasonal flooding to wash away human waste, which was often discarded in gutters, streets and open drains. During the rainy season, latrines frequently overflowed, dispersing parasite-laden faeces throughout neighbourhoods. Moreover, heavy deforestation around Seoul left surrounding slopes bare; during heavy rains, eroded soil washed into the city’s central stream, raising the riverbed and reducing its capacity. Repeated flooding spread waste across the capital (Kim et al. Reference Kim, Ki, Kim, Chai, Seo, Oh and Shin2014).

The problem became so severe that by the 18th century, the royal court initiated large-scale dredging projects. Although these efforts offered temporary relief, they did not fully resolve the issue, and only in the 20th century did improved urban infrastructure eliminate recurring floods and the associated dispersal of human waste (Kim et al. Reference Kim, Ki, Kim, Chai, Seo, Oh and Shin2014).

Taken together, in addition to parasitological examinations of coprolite samples from Joseon mummies – which clearly demonstrate that heavy parasitic infections were widespread among Koreans prior to the 20th century (Seo et al. Reference Seo, Oh, Hong, Chai, Cha, Bang, Cha, Wi, Park and Shin2017) – analyses of soil samples from archaeological sites have broadened this line of paleoparasitological research. Together, these approaches reveal wide-ranging patterns of environmental contamination and provide valuable insights into the reconstruction of social and environmental history in South Korea.

Toilets from a parasitological perspective

Paleoparasitological research in South Korea is closely integrated with archaeological surveys, as researchers often participate directly in fieldwork to collect samples for parasitological analysis. Their efforts focus on specific archaeological contexts – particularly ancient urban centres with dense populations or features related to toilet use – where organic waste and faecal material were most likely to accumulate and be preserved (Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021; Kim et al. Reference Kim, Seo, Fujita, Chai, Park, Jang, Jang and Shin2023). This targeted strategy greatly increases the effectiveness of archaeological parasitology and underscores the importance of carefully selected excavation contexts for successful sampling.

In South Korea, such studies are frequently carried out in conjunction with investigations of structures suspected to be ancient toilets (Shin et al. Reference Shin, Shim, Kim, Oh, Lee, Jung, Lee, Chai and Seo2014; Seo et al. Reference Seo, Chai, Kim, Shin, Ki and Shin2016; Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021; Kim et al. Reference Kim, Seo, Fujita, Chai, Park, Jang, Jang and Shin2023). This approach maximizes the likelihood of detecting preserved parasite eggs in archaeological specimens. Conversely, the recovery of parasite eggs from these contexts can also serve to confirm that the excavated structures were indeed ancient toilets (Shin et al. Reference Shin, Shim, Kim, Oh, Lee, Jung, Lee, Chai and Seo2014; Seo et al. Reference Seo, Chai, Kim, Shin, Ki and Shin2016; Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021; Kim et al. Reference Kim, Seo, Fujita, Chai, Park, Jang, Jang and Shin2023).

Toilets identified through parasitological techniques provide archaeologists and historians with important insights into the health conditions of past populations (Shin et al. Reference Shin, Shim, Kim, Oh, Lee, Jung, Lee, Chai and Seo2014; Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021; Kim et al. Reference Kim, Seo, Fujita, Chai, Park, Jang, Jang and Shin2023). Moreover, the ways in which these toilets were constructed offer clues about both the economic uses of human faeces and the building technologies of their time. For example, because most modern toilets are flush types, it is easy to assume that they are inherently superior to retention-type systems. The historical reality, however, is more complex. Cesspit toilets – not flush toilets – played a vital role in East Asian agricultural systems, as they served as reservoirs for night soil that was widely used as fertilizer (Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Ki et al. Reference Ki, Bae and Shin2013; Shin et al. Reference Shin, Shim, Kim, Oh, Lee, Jung, Lee, Chai and Seo2014; Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021; Fujita et al. Reference Fujita, Hong and Shin2023).

For this reason, cesspit toilets remained the most common type in East Asia until well into the 20th century. Such historical realities are difficult to reconstruct without the combined efforts of archaeologists and parasitologists, who work together to analyse ancient sanitation structures. In this sense, the study of toilet facilities constitutes an important branch of paleoparasitology in South Korea.

Study of toilets in South Korea and Japan

As human lifestyles evolved over time, patterns of parasitic infection also changed in parallel. Paleoparasitology has sought to clarify these relationships in concrete terms. Building on a growing body of data, researchers increasingly aim to reconstruct historical changes in parasitic infections in connection with broader societal and historical developments.

The contamination of Korean soil with parasite eggs prior to the 20th century indicates that large numbers of people were infected at the time. In particular, the soil in downtown Seoul was likely contaminated by toilet overflows during flooding, which dispersed parasite eggs contained in human faeces. From this, it follows that toilets excavated from pre-20th-century sites would contain substantial numbers of parasite eggs. This assumption ultimately provides the theoretical foundation for toilet archaeology in Korea.

Before turning to toilets and paleoparasitology in South Korea, it is useful to review the beginnings of toilet research in East Asia. In Japan, the analysis of parasite eggs recovered from archaeological sites began earlier than in any other East Asian country, providing scientific data about past societies that could not be obtained through conventional archaeological methods (Matsui et al. Reference Matsui, Kanehara and Kanehara2003). Because this work has focused largely on toilet-related archaeological features, the field eventually came to be known as toilet archaeology.

The development of toilet archaeology in Japan can be traced to the late 1980s, when an archaeological scientist visited the University of York to study environmental archaeology (Matsui et al. Reference Matsui, Kanehara and Kanehara2003). There, Matsui learned how to identify archaeological toilet structures and how to detect parasite eggs in excavated samples. Their pioneering work laid the foundation for what is now recognized as Japanese toilet archaeology (Matsui et al. Reference Matsui, Kanehara and Kanehara2003).

Before Matsui’s research began, structures suspected of being toilets had been reported from Japanese archaeological sites, but it was often difficult to demonstrate scientifically that these features had indeed served as latrines. Although scholarly interest in toilet-related features existed, full-scale scientific investigation did not occur until Matsui and his colleagues began systematic studies. This subfield quickly produced significant results and was soon acknowledged as an important area of archaeological science in Japan (Fujita et al. Reference Fujita, Hong and Shin2023).

The first confirmed identification of a pit latrine in Japan through parasite egg analysis occurred in 1992 at the site of the Fujiwara capital (Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Fujita et al. Reference Fujita, Hong and Shin2023). Since then, Matsui’s team has analysed samples from numerous sites across Japan, identifying a broad range of ancient parasite eggs.

Subsequent research has focused on documenting how toilet-related archaeological features changed over time. Long-term studies have enabled researchers to classify toilet structures by historical period, while analyses of parasite eggs recovered from these contexts have yielded valuable insights into the dietary habits of past populations (Ōta City Local History Museum, 1997; Fujita et al. Reference Fujita, Hong and Shin2023).

Overall, paleoparasitology in Japan has been conducted primarily in connection with toilet-related features. When archaeological verification of a toilet was difficult using conventional methods, the recovery of large numbers of parasite eggs from soil samples provided compelling evidence for their function. For instance, researchers identified human coprolites in a Jomon-period shell midden – interpreted either as a rudimentary toilet area or a dung heap (Matsui et al. Reference Matsui, Kanehara and Kanehara2003).

It remains uncertain whether early Japanese scholars explicitly conceptualized their work as toilet archaeology. Nevertheless, the strong emphasis placed on the structural aspects of ancient latrines fostered the development of a distinctive subfield without close parallels elsewhere. Because this work centred so heavily on toilet facilities, the analysis of parasite remains was often situated within a broader framework of toilet archaeology rather than as an independent line of paleoparasitological inquiry (Fujita et al. Reference Fujita, Hong and Shin2023).

Meanwhile, in contrast to Japan, the archaeological study of toilets in South Korea developed as a branch of paleoparasitology rather than as an independent field. Early paleoparasitological studies in Korea overlapped substantially with toilet archaeology in terms of subject matter, but the discipline soon expanded as researchers incorporated rapidly advancing analytical techniques from medicine and biology. The integration of modern technologies – together with the introduction of new sources of evidence, such as coprolites recovered from Joseon-period mummies – significantly broadened the scope of paleoparasitological inquiry and opened avenues of research that had previously been overlooked.

In South Korea, toilet archaeology did not evolve into a standalone subfield. Instead, it remained embedded within paleoparasitology, in part because the field was well positioned to absorb and apply cutting-edge scientific methods that have developed rapidly since the early 21st century. This environment facilitated the seamless incorporation of new techniques and materials, allowing paleoparasitology in Korea to grow in directions distinct from its Japanese counterpart.

Disposal of faecal waste in Neolithic Korea

The Neolithic period in Korea (approximately 8000–1500 BCE) was characterized primarily by hunter-gatherer and semi-sedentary lifeways, with the gradual introduction of early cultivation. To date, no archaeological evidence for dedicated toilet facilities has been identified from Neolithic contexts, and paleoparasitological evidence therefore relies mainly on preserved faecal materials such as coprolites recovered from shell middens. Over the past decades, research on ancient toilets in South Korea has yielded valuable insights into past societies, primarily for later prehistoric and historic periods (Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021) (Table 1). Palaeoparasitologists have identified parasite eggs in samples collected from both putative cesspits and flush-type facilities (Buyeo National Research Institute of Cultural Heritage, 2009a; Shin et al. Reference Shin, Shim, Kim, Oh, Lee, Jung, Lee, Chai and Seo2014). Such studies are essential for assessing the prevalence and extent of parasitism in ancient Korean society, although patterns of parasitism specifically associated with toilet contexts have not yet been fully clarified.

Table 1. Summary of paleoparasitological findings from major archaeological sites in South Korea

The historical and medical relationships among sedentary living, population density and parasitic infection are crucial for understanding the high infection rates observed in densely populated areas. Paleoparasitology has demonstrated that parasitic infections have never been uniform throughout human history (Reinhard and Araujo, Reference Reinhard, Araujo and Pearsall2008). Globally, infection patterns differed substantially between hunter-gatherers and agriculturalists. Before the emergence of farming, people generally led mobile lifestyles, moving in response to seasonal availability of wild resources. This mobility, combined with small group sizes and low population density, created conditions that were less conducive to sustained transmission of many parasites (Barnes, Reference Barnes2005).

In contrast, the onset of agriculture – the so-called Agricultural Revolution – brought population growth, settlement concentration and increased vulnerability to infection. Sedentary living allowed human habitation spaces to become increasingly contaminated with parasite eggs. Dependence on local water sources, reliance on cultivated crops and exposure to human waste within permanent settlements all increased the risk of infection among farming communities. Consequently, agriculturalists were far more vulnerable to parasitic infections than sparsely distributed hunter-gatherers (Barnes, Reference Barnes2005; Reinhard and Araujo, Reference Reinhard, Araujo and Pearsall2008; Reinhard et al. Reference Reinhard, Fujita and Shin2021; Fujita et al. Reference Fujita, Hong and Shin2023; Shin et al. Reference Shin, Fujita and Hong2023).

For broader East Asian context, comparative findings from the Japanese archipelago are briefly referenced below; however, the primary evidence for Neolithic Korea discussed here derives from coprolites recovered from shell middens. In Japan, coprolite studies from the Jomon-period Sannai-Maruyama site revealed almost no roundworm eggs, whereas Yayoi-period samples – dating to the rise of agriculture – showed frequent evidence of Ascaris infections (Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Fujita et al. Reference Fujita, Hong and Shin2023). These findings indicate a marked increase in roundworm prevalence following the introduction of farming. As population size and density increased during the Yayoi period, so too did the risk of soil-transmitted helminth infections (Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Fujita et al. Reference Fujita, Hong and Shin2023; Shin et al. Reference Shin, Fujita and Hong2023).

Similar contrasts appear elsewhere. In 17th-century Siberia, indigenous hunter-gatherer groups exhibited few soil-transmitted helminths, but coprolite analyses revealed frequent fish-borne parasites such as Diphyllobothrium and Opisthorchis species – likely acquired through consumption of raw or undercooked fish. These findings highlight the differing infection profiles of hunter-gatherers and agriculturalists: fish-borne parasites predominated among foragers, while soil-transmitted parasites were more common among farming populations (Slepchenko et al. Reference Slepchenko, Seo, Hong, Oh, Shin, Shin and Bianucci2021; Fujita et al. Reference Fujita, Hong and Shin2023).

Toilet archaeology in Japan initially focused on Jomon hunter-gatherer and Yayoi agricultural sites, although the precise location and form of toilets from these periods remain uncertain. Coprolites preserved in shell middens retained their original shape and texture remarkably well, making them ideal for analysis. Since the first coprolites were identified at Ōkita-machi (Miyagi Prefecture), additional examples have been found at sites such as Torihama Midden (Fukui Prefecture) and Satohama Midden (Miyagi Prefecture) (Fujita et al. Reference Fujita, Hong and Shin2023). These discoveries suggest that Jomon people may have defecated directly into midden deposits. Given the relatively low population density of the Jomon period, there was likely no need for dedicated toilet facilities (Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Fujita et al. Reference Fujita, Hong and Shin2023). The presence of Jomon-period toilets is currently being investigated by one of the authors (Fujita H.).

The situation in South Korea appears similar. No toilet structures have been identified from Neolithic sites, but coprolites have been recovered from shell middens of this period, such as those at Changnyeong Bibong-ri and Yoseodo. Parasitological analysis of the Yoseodo coprolites revealed eggs of Ascaris lumbricoides, Clonorchis sinensis and Toxocara species. The presence of C. sinensis indicates that Neolithic Koreans consumed raw freshwater fish, while Toxocara infection suggests that dogs – likely hosts to these parasites – lived alongside humans in the settlements (An et al. Reference An, Seo and Kim2008).

Of particular interest is the discovery of A. lumbricoides eggs in Neolithic Korean contexts. This contrasts with Jomon-period Japan, where shell middens of the same era have not yielded roundworm eggs, most likely because agriculture had not yet been introduced. Although Neolithic agriculture in Korea was less developed than in the later Bronze Age, the evidence suggests that some form of cultivation existed, contributing to roundworm transmission.

Nevertheless, as in the Jomon period of the Japanese archipelago, Neolithic Koreans do not appear to have used separate toilet facilities and likely defecated in outdoor areas such as shell mounds. Large-scale construction of dedicated toilets had not yet begun during this period.

Disposal of faecal waste in the Bronze Age and Early Iron Age

The Korean Bronze Age (approximately 1500 BCE–300 BCE) and Early Iron Age (approximately 300 BCE–0 BCE) were characterized by expanding agriculture and increasing settlement density; however, no toilet structures from these periods have been conclusively identified, and evidence for faecal waste disposal is therefore indirect. In Korean history, the Bronze Age marked the beginning of intensive agriculture, particularly rice cultivation. Villages equipped with bronze tools, weapons and defensive facilities emerged, reflecting a clear trend towards increasing social complexity. Communities practicing advanced farming techniques gathered to form densely populated settlements. This farming culture then spread to the Japanese archipelago, where it began the Yayoi period (Miyamoto, Reference Miyamoto2022).

Parasitological findings confirm that the spread of agriculture was closely tied to rising infection rates. At Yayoi-period sites in Japan – an agrarian society closely connected to Korea’s Bronze Age and Early Iron Age – numerous soil-transmitted parasites have been identified, in contrast to their rarity in the preceding Jomon period (Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Fujita et al. Reference Fujita, Hong and Shin2023). This shift was evidently driven by the onset of intensive rice cultivation and the accompanying social transformations.

In Korea, too, agricultural expansion during and after the Bronze Age exposed populations to heavy parasitic infections. This is evidenced by paleoparasitological research at Sinchang-dong, a wetland site of the Early Iron Age in southern Korea (Figure 1). Analyses of remains from this site, which vividly reflect daily life before the Common Era, revealed multiple parasite eggs, indicating that infection rates among the Bronze Age people were considerably high at the time (Gwangju National Museum, 2009).

The comparison between Korea’s Bronze Age–Early Iron Age and Japan’s Yayoi period is highly instructive, as Yayoi culture was shaped in part by the migration of Korean Bronze Age populations and subsequently developed in close cultural connection with them (Shinoda and Fujio, Reference Shinoda and Fujio2025). During this era, cultural elements such as rice farming, the use of metal tools and the raising of domesticated animals were transmitted from the continent to Japan (Miyamoto, Reference Miyamoto2022). As a result, from the Yayoi period onward, the ancient cultures of Korea and Japan shared many features in common for a considerable span of time. Consequently, archaeological findings from one country often inform interpretations in the other, since continental cultural influences generated strong parallels between the 2 regions (Figure 1).

Figure 1. Archaeological and historical timelines of Korea and Japan.

During the Yayoi period, intensive farming spurred population growth relative to the Jomon era, leading to social conflict and the construction of moated defensive settlements. Archaeological and parasitological evidence shows that these communities suffered heavily from soil-transmitted parasites, unlike their Jomon predecessors (Matsui et al. Reference Matsui, Kanehara and Kanehara2003). Although no Yayoi-period toilets have yet been definitively identified, Ascaris and Trichuris eggs were recovered from moat fills at the Ikegami–Sone site in Izumi City, Osaka Prefecture. These findings suggest that human excrement from within the settlement was washed into the moats by rainfall. While moats were originally assumed to have served solely as military defences, the discovery of parasite eggs indicates that they may also have functioned in drainage and waste disposal during Yayoi period (Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Fujita et al. Reference Fujita, Hong and Shin2023).

Similar moated settlements were plentifully constructed during the Bronze Age on the Korean Peninsula, where they first appeared before subsequent spreading to Japanese archipelago (Figure 1). These moated sites reported from Yayoi ruins share many characteristics with their Korean counterparts. As in Japan, no direct evidence of toilets has been found in Bronze Age settlements. Considering parasite traces being recovered from secondary features such as moats at Yayoi sites, we reasonably infer that Bronze Age Korean communities may likewise have used moats for the disposal of human waste, with faeces likely washed away during the rainy season. Although direct evidence is lacking for the Bronze Age, parasitological analysis of settlement moats from the later Three Kingdoms period has confirmed traces of human faecal contamination (Shin et al. Reference Shin, Oh, Chung, Yi, Chai and Seo2009). This suggests that the use of moats for waste disposal was not an unfamiliar practice in Korean history either.

We note that the Bronze-Age pits were uncovered at Songjeong-ri, Geochang. Although a preliminary investigation points to the possible existence of toilet facilities at the site, final confirmation remains pending, as parasitological testing of soil samples from the feature showed negative results. In addition to toilets, the possibility of storage, tombs, traps and water purification facilities were also checked, but no clear results were obtained in either case. Only the chemical analysis showed that the total potassium content was generally similar to the compost content made from modern livestock faeces (The BuKyung Cultural Relics Research Institute, 2017).

For the presence of Bronze Age toilets, conclusions must be drawn cautiously, given the strong historical and cultural parallels between Korean (Bronze and Early Iron Age) and Japanese (Yayoi) societies (Figure 1). The absence of direct toilet remains in Yayoi-period Japan underscores the need for further investigation (e.g. parasitological evidence) of Bronze Age ruins in South Korea, especially in light of the close cultural interconnectedness of the 2 countries during this period.

Toilets in the Three Kingdoms period and Unified Silla

In Korea, with the rise of the Three Kingdoms on the Korean Peninsula and in southern Manchuria around the 1st century CE, society entered a new stage of development. For the first time in Korean history, properly designed toilets began to be constructed. Toilet facilities identified in archaeological ruins from the Three Kingdoms period became increasingly sophisticated by the time of Unified Silla, which consolidated the 3 earlier kingdoms (Table 1 and Figure 1).

One of the most representative examples is the facility located in the royal palace at Wanggung-ri, Iksan – the adjunct capital of the Baekje Kingdom in the southwestern Korean Peninsula (Buyeo National Research Institute of Cultural Heritage, 2009a; Seo and Shin, Reference Seo, Shin and Mitchell2015). Archaeologists uncovered the remains of an ancient toilet at this site, part of a royal residence built in the early 7th century. Specimens recovered from the probable toilet contained numerous parasite eggs, including Ascaris, Trichuris and Clonorchis species. Based on both architectural features and parasitological evidence, the structure was identified as a palace toilet. Excavation further revealed that the Baekje people constructed a cesspit, surrounded it with pillars and installed toilet blocks inside. A particularly notable feature was a sewage canal connecting the toilet to the exterior of the residence, likely designed to channel wastewater away (Figure 2) (Buyeo National Research Institute of Cultural Heritage, 2009a; Seo and Shin, Reference Seo, Shin and Mitchell2015).

Figure 2. The 7th-century palace at Wanggung-ri, Iksan, the adjunct capital of the Baekje Kingdom. (A) Sewage canals connected the toilets to the exterior of the palace, likely designed to channel wastewater away. (B) Wanggung-ri toilet (Courtesy of the Buyeo National Research Institute of Cultural Heritage).

At the Wanggung-ri site, among 3 toilets discovered at the palace, the largest measured 10.8 m in length, 1.8 m in width and 3.4 m in depth. Smaller internal blocks suggest that this toilet was intended for simultaneous use by individuals of lower social status, while another, designed for a single user, appears to have been reserved for dignitaries (Buyeo National Research Institute of Cultural Heritage, 2009a; Seo and Shin, Reference Seo, Shin and Mitchell2015).

In brief, the Wanggung-ri complex represents one of the best examples of toilet facilities maintained by a royal palace on the Korean Peninsula. The toilets were precisely engineered, featuring drainage channels integrated with the toilet structures. The discovery of the Wanggung-ri helped resolve long-standing academic debates regarding the identification and function of toilets in ancient Korean settlements.

In East Asia, cesspit toilets were widely used, functioning as reservoirs for night soil that farmers later transported to nearby fields for use as fertilizer once the pits were full (Shin et al. Reference Shin, Shim, Kim, Oh, Lee, Jung, Lee, Chai and Seo2014; Seo et al. Reference Seo, Oh, Hong, Chai, Cha, Bang, Cha, Wi, Park and Shin2017). Archaeological research at Buyeo, the Baekje Kingdom’s capital, uncovered additional possible cesspit toilet remains of the time. Soil samples taken from geological strata dating to the 6th–7th centuries CE at Gua-ri and Gatap-ri contained numerous organic materials preserved by the sites’ low-lying and moist topography. Parasitological analysis of soil from the pits revealed abundant parasite eggs, suggesting that these structures may have functioned as cesspit toilets or dung heaps (Figure 3).

Figure 3. Possible cesspit toilet remains from Gua-ri, the capital of the Baekje Kingdom (Shin et al. Reference Shin, Shim, Kim, Oh, Lee, Jung, Lee, Chai and Seo2014). (A) Cesspit toilet structure; (B) sample collection from the toilet; (C) Trichuris trichiura egg; (D) Ascaris lumbricoides egg identified in the samples.

Although these structures were not as elaborate as the royal palace toilet, their discovery contributes to understanding the types of toilets used by inhabitants of the ancient capital. Given the location in a royal capital, it is unlikely that faecal pits would have been left exposed if they were not functional toilets. It is plausible that some form of superstructure existed above the pits, serving as facilities for commoners living in the capital (Shin et al. Reference Shin, Shim, Kim, Oh, Lee, Jung, Lee, Chai and Seo2014).

In Japan, toilets have also been identified at sites corresponding to the Three Kingdoms and Unified Silla periods in Korea. During the Kofun (3rd–7th centuries CE) and Asuka (592–710 CE) periods, cultural influence from the continent extended even to sanitation practices. Archaeological evidence suggests that proper toilet construction began during the Kofun period, with both pit latrines and flushing toilets coming into use (Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Fujita et al. Reference Fujita, Hong and Shin2023).

The earliest pit latrine in Japan was identified at Fujiwara-kyō, and similar cesspits uncovered at Tsukusikan and Nagaokakyō have been linked to the use of human manure in farming (Ōta City Local History Museum, 1997; Matsui et al. Reference Matsui, Kanehara and Kanehara2003). More advanced cesspit toilets were later discovered in major urban centres such as Dazaifu, where they were found at Korokan, a guesthouse for diplomatic missions. Cesspit toilets have also been identified at Yanagi-no-gosho, the 12th-century elite residence of the Ōshū Fujiwara family in Hiraizumi (Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Fujita et al. Reference Fujita, Hong and Shin2023). Given the close connections between early agrarian cultures of Korea and Japan, cesspit toilets from these ancient kingdoms likely shared many similarities. However, further comparative research is needed, as the available archaeological evidence is still limited.

As in other ancient civilizations, flush toilets were also used in East Asia, and their scholarly study began in Japan as early as the 1990s. Notably, toilet archaeologists have proposed that flushing toilets in Japan may even predate pit latrines. Some researchers suggest that the disposal of human waste using flowing water originated during the Yayoi period. At the time, many villages were surrounded by defensive moats; and those moats likely received excrement and household wastewater, which were flushed away during rainfall or periods of rising water levels (Kanazawa and Miyakake, Reference Kanazawa and Miyakake1990; Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Fujita et al. Reference Fujita, Hong and Shin2023). The Japanese term kawa-ya (literally ‘river-house’), meaning ‘toilet’, may reflect this early practice of defecating into running water – a prototype of the flushing toilet (Matsui et al. Reference Matsui, Kanehara and Kanehara2003).

Further evidence includes large deposits of faeces and parasite eggs discovered in a 3rd-century conduit at Sakurai City, Nara Prefecture, interpreted as part of a flushing toilet (Matsui et al. Reference Matsui, Kanehara and Kanehara2003). More advanced flushing toilets were later identified at Heijō-kyō, designed to discharge waste into roadside drainage channels functioning as sewers. Recovery of parasite eggs from these features provided definitive proof of their use as toilets (Matsui, Reference Matsui and HUMAN AND ENVIRONMENTAL FORUM Editorial Committee2001; Matsui et al. Reference Matsui, Kanehara and Kanehara2003; Fujita et al. Reference Fujita, Hong and Shin2023). Additional flush toilets have also been reported from Fujiwara-kyō and Akita Castle (Ōta City Local History Museum, 1997).

Similarly, in Korea, primitive forms of flushing toilets may have been used in prehistory, but definitive archaeological evidence begins with the Three Kingdoms period (Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021). At the Hwajisan royal villa of the Baekje Kingdom (6th–7th centuries CE), archaeologists identified a wooden structure resembling a flush toilet. The structure was connected via a water channel to a nearby stream, allowing continuously flowing water to remove excrement. Soil samples yielded T. trichiura, A. lumbricoides, C. sinensis and Trichuris vulpis eggs – confirming the function of the structure and its water channel as a Baekje-period flush toilet (Figure 4). This discovery indicates that flush toilets were used among Korea’s elite by at least the 6th–7th centuries (Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021).

Figure 4. Flush toilet from the Hwajisan royal villa of the Baekje Kingdom (6th–7th century) (Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021). (A) Wooden structure resembling a flush toilet; (B) toilet structure connected by a water channel to a nearby stream; (C, D) Trichuris trichiura eggs; (E) Ascaris lumbricoides egg identified in the specimen.

Even at the Wanggung-ri palace site discussed earlier, where a cesspit toilet was identified, archaeologists argue that its design was more elaborate than the typical cesspit arrangements of the period. Because the presumed toilet was connected to a sewage canal directing waste towards the palace perimeter, some scholars believe that a rudimentary flush system – discharging waste into a flowing drain – had been partially introduced at Wanggung-ri (Buyeo National Research Institute of Cultural Heritage, 2009a).

Another example comparable to the flush toilets of Hwajisan and Heijō-kyō was uncovered at the Donggung Palace site of the Silla Kingdom (57 BCE–935 CE). Building No. 29, measuring 5.8 m east–west and 3.1 m north–south, contained 4 rectangular cornerstones and a floor lined with roof tiles. Two elongated steppingstones were identified inside, likely used as toilet fixtures. Outside the building, a water culvert connected to the interior and passed beneath the steppingstones. Beneath these stones, a perforated stone was found, suggesting that these components together formed a functioning toilet. Water is believed to have entered from the south and exited to the west, enabling the system to operate as a flush-type toilet (Figure 5). The structure dates to approximately the 8th century CE (Gyeongju National Research Institute of Cultural Heritage, 2019; Oh et al. Reference Oh, Shim, Kim, Hong, Chai, Fujita, Seo and Shin2021).

Figure 5. Flush toilet from the Donggung Palace site of the Silla Kingdom (57 BCE–935 CE). (A) Building No. 29; (B) water channel; (C) 2 elongated steppingstones identified inside the building; (D) realigned stone structures forming the flush toilet (Courtesy of the Gyeongju National Research Institute of Cultural Heritage).

This example from the Silla royal palace represents the pinnacle of ancient Korean toilet architecture, showcasing a remarkably advanced and complete flush system. It is the most sophisticated ancient Korean toilet reported to date, reflecting a high level of technological achievement. Notably, royal palace toilets in Korea were consistently constructed with elongated pits – a design feature inherited by the palace toilets of the Joseon Dynasty (1392–1910 CE). This continuity suggests that specialized toilet construction techniques were preserved and transmitted across centuries.

Toilets of the Goryeo and Joseon Dynasties

To date, no toilets from the Goryeo Dynasty (918–1392 CE) have been conclusively identified through archaeological investigations in South Korea (Lim, Reference Lim2023). Considering that numerous toilet remains have been reported from sites dating to the Three Kingdoms and Unified Silla periods, it is highly likely that such facilities also existed during the Goryeo era. The absence of securely identified examples may reflect insufficient archaeological investigation or the poor preservation of toilet structures from this period. Further discoveries from Goryeo sites will be essential to clarify this issue.

The number of toilets known from the succeeding Joseon Dynasty (1392–1910 CE) is likewise small (Table 1). Because the Joseon period is relatively recent and archaeological research in South Korea has tended to focus more heavily on earlier periods, it is possible that relatively few toilets have been reported for these later centuries.

Despite the limited number of discoveries, the toilets identified from the Joseon Dynasty were constructed to a remarkably high standard. Three examples have been identified: those excavated at Hoeamsaji Temple in Yangju, at the Baekseokdongcheon Stream site in Buam-dong, Seoul, and in the Donggung (East Palace for the Crown Prince) area of Gyeongbokgung Palace, the royal residence of the Joseon state. These facilities were associated with large temples, elite villas and royal palaces, respectively, and thus represent high-status contexts. As such, they cannot be considered representative of toilets used by the general population (Lim, Reference Lim2023).

All 3 structures were carefully built in a rectangular form using stone, and each was notable for its systematic waste-treatment design. Two examples – the Hoeamsaji and Baekseokdongcheon Stream sites – were simple cesspit toilets in which excrement accumulated in the subterranean stone chamber and was later manually removed (Lim, Reference Lim2023).

The Hoeamsaji toilet consisted of a single-story wooden building constructed on level ground. Beneath it, a stone-lined chamber was installed for the accumulation of manure. The walls and floor of the chamber were built of stone, and once the manure reached a certain level it was lifted out and used as fertilizer. The Baekseokdongcheon Stream facility is believed to have served an elite villa frequently visited by upper-class scholars. After use, the excrement appears to have been covered with ash or straw to facilitate later removal for agricultural use (Lim, Reference Lim2023).

In contrast, the Joseon palace toilet represented a more advanced system, combining both cesspit and flushing elements. Measuring 1.4 m in width, 10.4 m in length and 1.6–1.8 m in height, the structure appears to have been designed so that water entered through an inlet on the north side, mixed with faeces in a septic chamber and was discharged through an outlet after partial separation (Figure 6) (Ganghwa National Research Institute of Cultural Heritage, 2022). This design reflects the high technical level of toilet construction maintained in the royal palace during the Joseon Dynasty. Notably, the elongated form of the toilet pit closely resembles the toilets of ancient Korean kingdoms, such as the Baekje facilities excavated at Wanggung-ri (Lim, Reference Lim2023).

Figure 6. Palace toilet of the Joseon Kingdom. (A) Area of investigated toilet remains (red shaded); (B) toilet structure (red shaded); (C) interior of the septic tank; (D) water inlet; (E) water outlet (Courtesy of Ganghwa National Research Institute of Cultural Heritage).

All 3 toilets discussed here were uncovered from Joseon-period contexts and represent well-constructed facilities used by the uppermost social classes of the time. Additionally, separate surveys have been conducted on toilets used by individuals of lower status, providing a broader perspective on sanitary practices across different social strata.

Colonial period

The Japanese colonial period in Korea (1910–1945) represents a transitional phase in the development of sanitation systems in South Korea. Archaeological evidence for toilet structures from the first half of the 20th century in South Korea is extremely limited (Table 1). In 2021, an investigation was conducted at the Sewoon Reorganization Promotion Zone in Ipjeong-dong, Seoul, located in the southeastern part of Old Seoul City (Kim et al. Reference Kim, Seo, Fujita, Chai, Park, Jang, Jang and Shin2023). The excavated architectural remains were dated to the late 19th to early 20th century, and among them, a wooden structure resembling a toilet was discovered. This toilet-like feature had been constructed by stacking 2 wooden barrels, whose interiors were filled with soil and organic sediments. Based on inscriptions identifying a Japanese liquor manufacturer and a vinegar company, the structure is thought to date to the early 20th century (Kim et al. Reference Kim, Seo, Fujita, Chai, Park, Jang, Jang and Shin2023) (Figure 7).

Figure 7. (A) and (B) Colonial period toilet found at the Sewoon Reorganization Promotion Zone in Ipjeong-dong, Seoul (Kim et al. Reference Kim, Seo, Fujita, Chai, Park, Jang, Jang and Shin2023). The toilet structure was constructed by stacking 2 wooden barrels. (C) Trichuris trichiura egg found in toilet sample.

Soil samples recovered from inside the barrels contained parasite eggs of Trichuris trichiura, unfertilized Ascaris lumbricoides and Taenia species, strongly suggesting that the barrels functioned as a toilet during that period. The use of wooden barrels for toilet construction was a traditional practice during the Edo period in Japan, indicating that this barrel toilet was likely used by Japanese residents of Seoul during the colonial period (1910–1945 CE). This finding demonstrates that Japanese settlers constructed and used toilets in Seoul that closely resembled those in their homeland (Kim et al. Reference Kim, Seo, Fujita, Chai, Park, Jang, Jang and Shin2023) (Figure 7).

Comparable evidence has been reported from Taiwan. Yeh et al. (Reference Yeh, Cheng, Huang, Zhan, Wong and Mitchell2019) examined specimens from a Japanese police outpost active between 1921 and 1944 and identified parasite eggs of Eurytrema species, T. trichiura and A. lumbricoides. In East Asia, prior to the implementation of full-scale deworming programs, the prevalence of Ascaris infection was remarkably high – reaching nearly 60% in Japan in 1947 and in Korea in 1969 (Fujita et al. Reference Fujita, Hong and Shin2023). Taken together, parasitological data from early 20th-century toilets in South Korea, along with findings from the Japanese police outpost in Taiwan, indicate that Japanese populations living in colonial territories were also heavily infected with soil-transmitted parasites.