Debate on the spread of farming to Europe

The FLDH is now at the centre of a heated controversy in European archaeology (Kristiansen Reference Kristiansen2005) and linguistics (Chang et al. Reference Chang, Cathcart, Hall and Garrett2015; Hammarström Reference Hammarström2010; Ross Reference Ross2006). To understand the nature and logic of the FLDH, we here briefly review how European archaeology has viewed the Neolithization of Europe. While European archaeologists have long been interested in the Neolithization of Europe since the time of V.G. Childe, it was not until the 1970s and 1980s that archaeologists began to focus their attention on how farming spread throughout Europe – that is, the mechanisms behind the spread of farming. The spread of farming in Europe can roughly be divided into three perspectives: migrationist, adoptionist and interactionist.

Migrationist views have the longest history. Ammerman and Cavalli-Sforza (Reference Ammerman, Cavalli-Sforza and Renfrew1973, Reference Ammerman and Cavalli-Sforza1984) have suggested that Neolithic farmers spread through a series of colonizations of neighbouring lands, characterizing the spread of agriculture as a ‘wave of advance’. Using radiocarbon dates, they suggested that Neolithic adaptations and material culture spread gradually across Europe and argued that this dispersion took the form of human colonization. They also suggested that this pattern was best explained by rates of population growth and that individual episodes of migrations resembled ‘waves’ of population expansion. This model has had a critical impact on thinking about the spread of not only human populations but also agriculture. However, this model has also been criticized for adhering to Childe's simplistic notion of European Neolithization (Price Reference Price and Price2000; Price et al. Reference Price, Gebauer, Keeley, Price and Gebauer1995; Whittle Reference Whittle1996). This model essentially describes how farmers spread across Europe, paying little attention to regional diversity, changes in material culture and causal mechanisms.

The notion of the farmer as colonizer has continued to influence later studies examining the spread of farming. Several refined versions of the colonization model that concentrate to a greater degree on the rapidity of the spread of farming have been put forward by researchers. These models often suggest that long-distance migration or ‘leapfrog colonization’, which entailed leaping strides over long distances and ‘frontiers’ rather than a gradual expansion of populations into neighbouring lands, was the characteristic mechanism of the Neolithic spread (Bogucki Reference Bogucki1988, Reference Bogucki and Price2000; Dennell Reference Dennell, Green and Perlman1985; Keeley Reference Keeley, Gebauer and Price1992; Milisauskas and Kruk Reference Milisauskas and Kruk1989; Moore Reference Moore, Green and Perlman1985). These models aim to explain the apparent rapidity of the spread of farming. Nevertheless, since they focus solely on the existence of ‘frontiers’, these models rarely attempt to explain what happened to Mesolithic foragers when farmers migrated into their lands. Indigenous foragers are implicitly seen as having been expelled to marginal areas, leaving uninhabited areas open to occupation by farmers (for exceptions, see Bogucki Reference Bogucki1988; Moore Reference Moore, Green and Perlman1985).

Adoptionists, focusing on the presence of indigenous hunter–gatherers in Europe rather than frontiers, suggest that the spread of agriculture resulted from indigenous adoption by Mesolithic populations. Central to this perspective is the active role indigenous hunter–gatherers played in the spread of farming, a notion that migrationists have largely neglected. For example, Whittle (Reference Whittle1996) suggests active adoption by indigenous Mesolithic hunter–gatherers of Neolithic ideas, animals and plants of Middle Eastern origin.

Meanwhile, interactionists take an eclectic view. Assuming both the existence of agricultural frontiers and an active role for indigenous Mesolithic hunter–gatherers, they focus on interactions between indigenous foragers and migrant farmers. Gregg (Reference Gregg1988, Reference Gregg and Gregg1991) argues that interactions between farmers and foragers produced benefits for each group. In her terminology, ‘indirect food production’ played an important role in the process of the spread of farming. Zvelebil and Rowley-Conwy (Reference Zvelebil and Rowley-Conwy1984) argued that various exchanges took place between foragers and farmers before foragers adopted agriculture. Zvelebil and Lillie (Reference Zvelebil, Lillie and Price2000), synthesizing existing models of forager–farmer interaction, attempt to explain various interactions between indigenous foragers and migrant farmers in what they call the ‘forager–farmer frontier zone’. Although the history of these models is brief, the forager–farmer interaction models provide a new perspective on the study of the spread of agriculture by focusing on the dynamic reactions of foragers to farming.

Both the indigenous adoption and interaction models emphasize the role of indigenous foragers in the spread of farming in Europe, a factor that migrationists hardly address. By the early 2000s, many European archaeologists seemed to lean towards accepting the existence (and significance) of forager–farmer interaction and appeared to have reached a consensus on two points. First, a single mechanism cannot explain every transition from foraging to farming across the vast area of Europe, but instead diverse mechanisms were involved in the processes of transition. Second, the simple dichotomy between colonization and indigenous adoption is problematic. Both colonization by farmers and the reactions of indigenous foragers varied in different places and some kind of ‘contact’ between the two existed throughout the process of the spread of farming.

It was under these circumstances that the FLDH broke into European archaeology in the 1990s and early 2000s (e.g. Bellwood Reference Bellwood2001). The FLDH was highly controversial because it not only takes an extreme form of the migrationist argument but also connects the spread of farming directly to the dispersal of the proto-Indo-European language, a topic that had rarely been discussed in archaeology. It was first proposed by Renfrew (Reference Renfrew1987) in the late 1980s, but was not very influential in European archaeology until genetic studies that supported this hypothesis were published in the early 2000s (e.g. Forster and Toth Reference Forster and Toth2003). While the FLDH was originally Europe-specific, Bellwood (Reference Bellwood2005) soon attempted to apply it to Africa, Asia and America, arguing that farming and related cultivars were mostly spread through processes of migration. Not surprisingly, many archaeologists immediately pointed out many of the epistemological and empirical problems with this argument (e.g. Kristiansen Reference Kristiansen2005). In contrast, some historical linguists seemed to welcome and adopt it as a theoretical basis for inferring the timing and routes of language dispersal in many areas.

General considerations of migration, diffusion and adoption

Simply put, one of the central points of the debate between migrationist (including the FLDH), adoptionist and interactionist perspectives is the question of how non-local elements appear in a particular area. When non-local elements such as ideas, technologies, styles and items appear in an area, four heuristic mechanisms can be taken into consideration, each of which has a different implication: either the element was (a) brought by migrants, (b) moved through some sort of exchange, (c) copied or adopted by local people, or (d) made by migrants and/or local people who learned how to make it through intensive interaction (Hegmon et al. Reference Hegmon, Nelson and Ennes2000: 218). In archaeology, it is important to distinguish these different mechanisms because the archaeological picture and our understanding of the past are critically affected by the way in which a model uses these mechanisms, as we have seen in the debate between the migrationists and adoptionists. Focusing on diffusion and migration, we here discuss the different processes implied by these two mechanisms and how they can be archaeologically distinguished.

Is FLDH a general theory or model?

The FLDH is a hypothesis originally designed to explain the spread of farming and the proto-Indo European Language family in Europe. However, its utility as a general model that can be applied to all parts of the world has yet to be demonstrated. It can be inferred that many occurrences of the spread of farming probably resulted from migrations of farmers, because, as Bellwood (Reference Bellwood2005) argues, continuous farming at one locale in general tends to result in population increase and also a decrease in soil productivity, providing a motivation for dispersal. However, it is not always the case that the spread of farming and the appearance of non-local cultivars can be explained by the migration of farmers. As seen above, new technology and cultural elements spread for various reasons, and the mechanisms involved in their spread also vary (Kim Reference Kim2001, 2003). The relationship between the spread of farming and the migration of farmers cannot always be assumed, and therefore, the unconditional application of the FLDH to all regions of the world is not only theoretically but also empirically risky. In fact, Renfrew (Reference Renfrew, Bellwood and Renfrew2003), the original developer of the FLDH, admits that this hypothesis is not to be applied globally, and Bellwood (Reference Bellwood2005), who attempted to apply the FLDH to other areas, also states that, although farming is a major factor that may encourage population dispersal, it is not the only one. Even in its application to the European Neolithic, the FLDH is controversial (Chang et al. Reference Chang, Cathcart, Hall and Garrett2015; Kristiansen Reference Kristiansen2005), and most European archaeologists agree that the migration of farmers cannot comprehensively explain the regional and temporal variability observed in the spread of farming to Europe (Price Reference Price and Price2000; Robb Reference Robb2013). While there are some areas where the migration of farmers accounts for the Neolithization of Europe, there also are many areas where indigenous adoption, assimilation or continuous interaction between farmers and Mesolithic foragers better explains the transition to farming (Robb Reference Robb2013).

Was the migration of farmers the only form of migration that led to language dispersal?

A reasonable explanation for the spread of a language family is that its speakers expanded spatially along with it. However, the migration of farmers is not the only form of migration that can be linked to language dispersal. Migrations have taken place throughout human history for various reasons, often unrelated to farming, and on various scales. Population reorganization resulting from factors unrelated to farming may provide a better explanation for language dispersal than farming in some instances. Kristiansen (Reference Kristiansen2005) points out that even though the spread of farming in Europe may have been related with the spread of farmers, as the FLDH assumes, this cannot be the only episode of migration that resulted in the dispersal of proto-Indo-European languages. He emphasizes the importance of the establishment of new international networks connecting Bronze Age societies throughout Eurasia and the Aegean during the early second millennium BC in accounting for the widespread appearance of Proto-Indo-European institutions and material culture. A statistical phylogenetic analysis carried out by Chang et al. (Reference Chang, Cathcart, Hall and Garrett2015) suggests that Indo-European language dispersal was not driven by the spread of farming, but rather, that Indo-European languages originated in the Pontic–Caspian steppe and spread together with cultural innovations associated with pastoralism beginning c. 4500–3500 BCE (p. 194). While determining which argument is a better explanation of the spread of the Proto-Indo-European languages is a matter that needs further scrutiny beyond the scope of this paper, in our view, assuming that the timing of a specific language is directly linked to the migration of a farming group, as the FLDH does, is risky, and drawing such conclusions should require strong empirical support.

Does the migration of farmers automatically lead to linguistic change?

In connecting the spread of farming to language dispersal, the first thing to assess is (a) whether or not the migration of farmers really led to the spread of farming in the given context and (b) whether migration provides a better explanation compared with other mechanisms such as indigenous adoption, cultural diffusion and information flow. Even in the case that migration is the best explanation, we need to also evaluate (c) whether the migration actually led to a linguistic change. In some cases, the spread of farmers may not necessarily have led to an alteration of language in host areas, especially when the size of the migrant group was not large enough and thus integrated into the host society within a short timespan. As discussed above, migration often occurs when people cannot stay in their homelands and leaving is less costly than staying. Therefore, migration involves decisions regarding whether to stay or leave and the decision-making units are usually households (or a community, at the largest scale) rather than regional populations (Kim Reference Kim2002b). Furthermore, following their arrival in a host's territory, they are often a minority population. Even when the size of migrant groups becomes large owing to a series of migrations, they may not be able to change the culture and language of their host societies. Also, host populations may adopt farming from migrant farmers without changing their language, even in cases in which they may adopt or borrow specific terms associated with farming.

The introduction of millet to Korea

In Korea, millet first appeared in the Chulmun Period (6000–1300 BCE). The Chulmun Period was characterized by a hunter–gatherer–fisher economy in which pottery was used, although there was extreme regional diversity in subsistence strategies, stone tool assemblages, pottery styles and the major resources utilized (Ahn et al. Reference Ahn, Kim and Hwang2015; Lim Reference Lim2012; Kim Reference Kim2003a, Reference Kim, Grier, Kim and Uchiyama2006). Freshwater fishing and the collection of various plant resources were a major part of the Chulmun subsistence economy, evidenced by findings of stone tools such as net sinkers, fishhooks and points, and the remains of wild plants such as acorns and nuts. The exploitation of sea resources was another important part of the subsistence economy. Shell middens dated from early to the latest Chulmun are densely distributed along the coast and on offshore islands of the Korean Peninsula (Kim Reference Kim, Grier, Kim and Uchiyama2006, Reference Kim2010). Considering these various data, many Korean archaeologists have reached a consensus that the Chulmun subsistence economy was a broad-spectrum foraging economy (Ahn Reference Ahn1994; Ahn et al. Reference Ahn, Kim and Hwang2015; Kim Reference Kim2010).

Around 3500 BCE, reliable evidence for millet cultivation appears. Domesticated foxtail and broomcorn millets have been identified from flotation samples (Crawford and Lee Reference Crawford and Lee2003; Lee Reference Lee2011) and impressions on pottery (Nakayama Reference Nakayama2014). So far, millets have been reported from 87 features (mostly houses, outdoor features and middens) from 18 sites (see Ahn et al. Reference Ahn, Kim and Hwang2015 for details). Since there is no evidence for in situ domestication of millet in Korea, it is thought that millet was introduced from northeast China where millet cultivation had been already in practice (Ahn et al. Reference Ahn, Kim and Hwang2015).

However, the introduction of millet does not appear to have had a major impact on Chulmun material culture and its subsistence economy. While pottery styles clearly differ between northeast China and the Korean Peninsula, an influx of northeast Chinese pottery styles into Korea has not been detected, and the styles of the two areas remain distinct long after the appearance of millet with little change in Chulmun pottery styles over time (Lim Reference Lim2012). The stone tool assemblages of Chulmun sites remain unchanged, showing continuing heavy dependence on hunting and fishing and the gathering of wild plants (Ahn et al. Reference Ahn, Kim and Hwang2015; Kim Reference Kim2010). There is also no indication of significant changes in settlement patterns and land-use strategies, and the hundreds of shell middens discovered along the coast and on islands continue to be used throughout the period (Kim Reference Kim2010). Isotopes analyses on human bones that postdate the introduction of millets also clearly indicate that Chulmun people depended heavily on sea resources and wild plants (An Reference An2006; Bae et al. Reference Bae, Bae and Kim2013;Choy and Richards Reference Choy and Richards2010). Even setting aside the issue of whether or not the presence of millets in archaeological features clearly indicates that millets were both cultivated and consumed, these lines of evidence suggest that millet cultivation during the Chulmun Period was not a major subsistence strategy but only an auxiliary activity that was added to the existing hunter–gatherer–fisher economy, possibly for the purpose of diversifying resources (Ahn et al. Reference Ahn, Kim and Hwang2015; An Reference An2006; Kim Reference Kim2010).

After the introduction of millets, both the size of settlements and the number of houses decrease, as shown in the summed probability distributions of radiocarbon dates from houses, and this declining trend continues towards the end of the Chulmun Period (Figure 1). Some researchers have interpreted this change as reflecting population decline or an increase in the mobility of Chulmun hunter–gatherers, which would have probably resulted in lower visibility of archaeological sites (Ahn et al. Reference Ahn, Kim and Hwang2015; Lim Reference Lim2012). Although the cause of this change is not yet clear, it strongly suggests that the introduction of millet around 3500 BCE did not lead to a transition to a farming economy.

Figure 1. A summed probability distribution of radiocarbon dates from Chulmun houses (n = 350). Dates were calibrated and summed using IntCal 13 and OxCal v.4.3.2 (Bronk Ramsey Reference Bronk Ramsey2017).

The introduction of rice to Korea and Japan

Around 1300 BC, Korea witnessed dramatic, abrupt changes in both subsistence economies and material culture at a regional level: Chulmun material culture and subsistence economies suddenly disappeared, and the Mumun Period (1300–400 BCE) began. The shapes of dwellings and pottery styles changed fundamentally. New stone tools with new forms and functions appear and dominate the stone-tool assemblage. These marked changes in material culture were accompanied by an abrupt change in the subsistence economy (Kim Reference Kim2002a, Reference Kim2003a). The Mumun economy was heavily dependent on rice cultivation, which was new to the region. Not only does rice suddenly dominate archaeobotanical assemblages, but dry rice fields have also been located in the vicinity of many settlement sites (Ahn Reference Ahn2010). In some locales where natural marshes and bogs developed, wet farming was also practised, but dependence on wet farming was still limited compared with dry farming (Ahn Reference Ahn2010; Kim Reference Kim2003a).

It is widely accepted that Mumun material culture, rice-farming and associated stone-tool technologies moved from northeast China through northern Korea to central and southern Korea (Ahn Reference Ahn2010; Kim Reference Kim2003a). One striking feature of this shift is that its spread throughout the Korean Peninsula was strikingly rapid, leading to an abrupt regional-scale transition. The subsistence change between the Chulmun and Mumun periods was not the simple addition of rice cultivation to the Chulmun subsistence repertoire. Instead, it was the cessation of a foraging economy coincident with the appearance of rice cultivation, accompanied by marked changes in material culture and settlement patterns (Kim Reference Kim2003a). Furthermore, there seems to be no continuity in the location of sites between the Chulmun and Mumun periods.

In addition to the rapidity and abruptness of the transition, two important characteristics of the Mumun culture are (a) its spread as a package of material culture and subsistence economy and (b) homogeneity in both the subsistence economy and material culture after the spread throughout the region (Kim Reference Kim2002a, Reference Kim2003a). Mumun cultural elements did not spread variably but instead as a package. Although there are some variations in ceramic styles according to the decorations observed on the rims of vessels, the overall shape of the vessels, the structure of ceramic/stone tool assemblages and dwelling shapes are strikingly homogeneous throughout central and southern Korea (Kim, Reference Kim2002a). The regional diversity in stone tool assemblages and subsistence strategies during the Chulmun Period also disappears: the subsistence economy was now firmly concentrated on rice farming and stone tool assemblages become homogenous throughout the region.

These lines of evidence are in good accordance with many of the criteria for detecting migration listed above (Haury Reference Haury and Thompson1958; Rouse Reference Rouse and Thompson1958; Zvelebil Reference Zvelebil1981) and suggest that the rapidity of the spread and homogeneity of the new material culture and subsistence economy after their spread throughout the region were brought through the migration of farmers. Spatial analyses of earlier Mumun settlements also confirm that migration was critically involved in the geographic spread of the early Mumun culture in the region (Kim Reference Kim2002a). The summed probability density of radiocarbon dates from Korea, which archaeologists now widely employ to infer population dynamics, indicates a population boom starting from the beginning of the Mumun Period around 1300 BCE (roughly 3300 calibrated BP, Figure 2) (Oh et al. Reference Oh, Conte, Kang, Kim and Hwang2017). Nevertheless, the changes in subsistence economy and material culture and population increase should not simply be assumed to be the result of a conquest of farmers or ethnic replacement. Rather, Jangsuk Kim (Reference Kim2002a, Reference Kim2003a) has suggested that conflicts arising as a result of the different land-use strategies of the two economies (that is, indigenous Chulmun hunter–gatherers’ logistically mobile land use vs migrant farmers’ exclusive territoriality) caused an abrupt increase in the mobility costs of Chulmun hunter–gatherers, straining their subsistence economy. Under these conditions, Chulmun hunter–gatherers probably abandoned their subsistence strategies and were rapidly integrated into the Mumun farming economy. Then, the migration of rice farmers around 1300 BCE seems more likely to have resulted in language dispersal from northeast China to Korea than the introduction of millet in the fourth millennium BCE.

Figure 2. The distribution of the Songgukri Culture and non-Songgukri cultures.

Around 800 BCE, a new material culture complex known as the Songgukri Culture appears in the Geum River Valley and spreads to southwest Korea (Ahn Reference Ahn2010; Grier and Kim Reference Grier and Kim2012; Kim Reference Kim2003b, Reference Kim2014), while in central Korea the Early Mumum material culture persists with little change, resulting in the appearance of a spatial division in material culture and subsistence practices (Figure 2). During the ensuing period (800–400 BCE, the Middle Mumun), farming rapidly intensified with the adoption of wet rice farming and there is clear evidence of significantly increased social complexity (Kim Reference Kim2003b, Reference Kim2014). While some researchers (e.g. Lee Reference Lee2005) have attempted to locate the origins of the Songgukri Culture and wet farming outside of the Korean Peninsula, most Korean archaeologists agree that the development of the Songgukri Culture and the spread of wet farming in southwestern Korea were subsistence-technological innovations developed by local populations in order to solve a population–resource imbalance resulting from rapid population growth and reduced soil fertility owing to long, continuous farming in the Early Mumun Period (Kim Reference Kim2003b). However, it is still unknown why the Songgukri Culture and wet farming techniques remained confined spatially to southwestern Korea and did not spread to central Korea. In our view, the spatial division of material culture and subsistence strategies between central and southern Korea was largely the result of differences in environmental factors. Whereas marshes and bogs are well distributed in southern Korea, they are rare in the more mountainous central Korea, which would have made the construction and use of rice paddies far more costly in that area.

It is very likely that around 600–500 BCE part of the Songgukri population of southwestern Korea moved to the Japanese Archipelago, and Korean and Japanese archaeologists agree that wet farming of rice was brought to Kyushu by migrants from southern Korea (Kataoka Reference Kataoka1999; Lee Reference Lee2000; Yoo Reference Yoo2010). Houses, stone tools and ceramics associated with the Songgukri Culture are found as a package in western Japan. Songgukri-style houses, which are very distinctive in shape and structure and thus easily distinguished from local Yayoi houses, have been discovered from 326 settlements out of a total of 710 Yayoi settlements in western Japan, together with Songgukri-style stone tools and pottery (Yoo Reference Yoo2010). Archaeological evidence also suggests that somewhere between 600–400 BCE population decreased on the Korean Peninsula, while Kyushu, Japan witnessed a coincident population increase. While radiocarbon dates indicate that the Japanese Yayoi Period and rice cultivation began as early as 900 BCE, the number of Yayoi sites significantly increased from 600 to 400 BCE, and this increase coincided with the population decline of the Songgukri Culture (Figure 3; Oh Reference Oh2018). Although the reason for population decline in Korea at this time is not clear, the simultaneity of population decline in Korea and increase in Kyushu, Japan may be best explained by a large-scale migration of Songgukri farmers to Japan.

Figure 3. Population fluctuations of South Korea and northern Kyushu, Japan (modified from Oh Reference Oh2018). Dates on the x-axis are in calibrated BP. South Korean population fluctuations are estimated using a summed probability distribution of radiocarbon dates from houses. Population estimations for Northern Kyushu are based on pottery chronology.

Around 400–300 BCE, bronze slender daggers and other associated bronze items, such as mirrors and bells, appeared in Korea (Ahn Reference Ahn2010). Since these new bronze items were used earlier in northeast China, some Korean archaeologists have suggested that these were also brought by migrants from northeast China (Ahn Reference Ahn2010; Jo Reference Jo2005). However, settlements associated with this new material culture are very scarce and sparsely distributed, so it is not clear whether a sizeable migration actually occurred (Kim Reference Kim2009).

The spread of millet as evidence for language dispersal

Robbeets (Reference Robbeets, Robbeets and Savelyev2017b–Reference Robbeetsd) pays special attention to the introduction of millet into Korea in the Chulmun Period and attempts to link this process with the appearance of proto-Koreanic in the Korean Peninsula. Relying on the FLDH and also on Gyeong-Ah Lee's argument (Crawford and Lee Reference Crawford and Lee2003; Lee Reference Lee2011) that the introduction of millet eventually culminated in the transition to a farming economy, Robbeets assumes that millet, the first non-local cultivar produced in Korea, was introduced around 3500 BCE by farmers speaking proto-Koreanic migrating from Liaoning in present-day northeast China. However, as outlined above, because the Korean Peninsula was already occupied by Chulmun hunter–fisher–gatherers since at least 6000 BCE, a key to evaluating the millet hypothesis is determining whether millet was adopted by the Chulmun foragers (diffusion) or whether it was brought along as a part of a large-scale migration of farmers from Liaoning. If millet was introduced as a result of a large-scale migration of farmers from Liaoning, an archaeologically detectable influx of Liaoning culture and changes in material culture after the introduction of millet should be expected, because vessel shape, manufacturing technology and the design layout and motifs of Korean Chulmun pottery markedly differ from those of Liaoning pottery. However, there is no detectable appearance of elements of Liaoning material culture that accompanies the arrival of millets. In addition, there is no evidence to suggest that the introduction of millet had a significant impact on the existing Chulmun economy, throwing into question Lee's argument (Crawford and Lee Reference Crawford and Lee2003; Lee Reference Lee2011), on which the millet hypothesis heavily relies. Continuity observed in Chulmun stone tool assemblage strongly suggests that hunting, gathering and fishing persisted as major components of the Chulmun subsistence strategy, and isotope analyses on human bones dating later than 3500 BCE also support the notion that the Chulmun subsistence economy continued to rely heavily on hunting, gathering and fishing (Ahn et al. Reference Ahn, Kim and Hwang2015; An Reference An2006; Choy and Richards Reference Choy and Richards2010; Kim Reference Kim2010). Shortly after the appearance of millet, rather than the aggregation of farming villages, the Chulmun Period witnesses an increase in mobility and dependence on maritime resources and wild plants (Ahn et al. Reference Ahn, Kim and Hwang2015; Oh et al. Reference Oh, Conte, Kang, Kim and Hwang2017). If there had been a large-scale migration of farmers that was substantial enough to lead to linguistic change, we might expect that populations would increase following the migration. However, radiocarbon dates suggest that, while the Chulmun population increased before the appearance of millet, shortly after the introduction of millet around 3500 BCE, the population declined (Figure 1). An alternative explanation for these population trends is that, facing a population increase, Chulmun hunter–gatherers might have indigenously adopted millet as a supplementary resource, but it did not play a significant role in solving the resource–population imbalance. Even if millet was brought by some migrants from northeast China to Korea, archaeological evidence demonstrates that the scale of migration was probably not large enough to lead to a fundamental linguistic change or the dispersal of a linguistic family.

As far as proto-Koreanic language is concerned, the millet hypothesis does not conform well to archaeological records. More importantly, the hypothesis is based on an assumption that the FLDH is a general model, and thus, following the expectations of the FLDH, the first appearance of non-local cultivars in an area determines the timing, cause and process of language dispersal. While some terms associated with millet cultivation might have been introduced along with millet, the available archaeological evidence does not seem to correspond with a large-scale migration that would result in the spread of the proto-Koreanic language.

Rice and the dispersal of Japonic and Koreanic

In explaining the formation of Koreanic, Whitman (Reference Whitman2011) relies less on the FLDH than Robbeets, but still emphasizes the spread of farming to Korea and Japan as the primary mechanism for the dispersion of languages. From an archaeological perspective, the biggest difference is that he focuses on rice rather than millet. He suggests proto-Japonic entered the Korean Peninsula as rice was introduced around 1300 BC at the beginning of the Korean Mumun Period and then moved to the Japanese Archipelago around 800 BCE.

As discussed above, the transition from the Chulmun Period to the Mumun Period in Korea witnessed dramatic and abrupt changes in every aspect of material culture, subsistence technology and settlement patterns. Many lines of evidence indicate that a large-scale migration of farmers and exclusive occupation of resource patches that had been widely exploited by Chulmun hunter–gatherer–fishers led to the collapse of the Chulmun economy and an integration of the indigenous Chulmun groups into Mumun farming societies (Kim Reference Kim2002a, Reference Kim2003a). In this sense, the appearance of dry farming of rice in Korea around 1300 BCE is a much more plausible candidate for the dispersal of a new language to the peninsula than the introduction of millet around 3500 BCE. Whitman (Reference Whitman2011) also suggests that the migration of wet rice farmers from southern Korea to Japan resulted in the movement of proto-Japonic to Japan. This argument also conforms with the extensive distribution of Songgukri-style material culture in western Japan (Kataoka Reference Kataoka1999; Yoo Reference Yoo2010) and demographic changes in both Korea and Japan in this period (Figure 2). Regardless of the universality of the FLDH, archaeological data associated with the spread of rice farming into Korea and Japan correspond well with material expectations we would predict to observe in the process of a potential language dispersal.

However, Whitman's argument that the Koreanic language arrived from northeast China in Korea along with the introduction of the ‘slender bronze dagger’ (also called the ‘Korean-style Bronze dagger’) around 300 BCE deserves further scrutiny. Although some Korean archaeologists (e.g. Jo Reference Jo2005) argue that the appearance of slender bronze daggers was triggered by the Chinese Yan's attack on Gojoseon, a polity that was located in present-day northeast China, and a subsequent large-scale migration of refugees from Gojoseon to the Korean Peninsula, the nature and size of this migration is unclear. As stated above, the Songgukri Culture witnessed some degree of population decline, but it still densely occupied southern Korea when the slender dagger was introduced. In contrast, settlements associated with the Slender Dagger Culture are extremely sparse and found only in marginal areas, and bronze items associated with the Slender Dagger Culture appear only in elite burials (Kim Reference Kim2009). Some archaeologists have asserted that the scarcity of Slender Dagger Culture settlements is the result of a shift towards nomadic lifeways (Ahn Reference Ahn2010), but there is no archaeological evidence that suggests that the Slender Dagger people were nomadic.

Alternatively, Jangsuk Kim (Reference Kim2009) has suggested that while there might have been migrants from Gojoseon, they did not dominate the local Songgukri population. Rather, the scarcity of Slender Dagger settlements and their distribution in marginal areas may suggest that elites of the Songgukri Culture selectively accepted a relatively small number of bronze specialists from Gojoseon. If this were the case, the size and sociopolitical power of migrants from Gojoseon would probably not have been large enough to change the local language. This scenario does not lend support to Whitman's suggestion (Reference Whitman2011) that the proto-Koreanic language, which apparently differed from the existing Songgukri language (presumably proto-Japonic), entered Korea along with the slender dagger. At present, any archaeological arguments on this issue, especially regarding the size of the migrant population and post-migration relations between migrants (slender dagger producers) and hosts (the Songgukri population), inevitably rely on indirect, circumstantial evidence. Therefore, whether or not the appearance of the slender dagger led to the formation of proto-Koreanic in Korea is not a question that can be addressed with any certainty.

Some thoughts on proto-Koreanic and proto-Japanic

What does the above archaeological consideration tell us about the spread and divergence of the proto-Koreanic and proto-Japanic languages? Although prehistoric archaeology can provide valuable insight to historical linguistics, archaeologists will tend to remain agnostic on this issue. As many archaeological, anthropological and historical studies have indicated, there is no straightforward connection between material culture, ethnicity, subsistence economy and language (Barth Reference Barth and Barth1969; Binford Reference Binford and Renfrew1973; Gosden Reference Gosden1999; Jones Reference Jones1997; Roux Reference Roux2016), and thus, inferring the formations, expansions and divergences of languages in prehistory directly from the archaeological record requires a great degree of speculation. Despite the potential risks, we here suggest a few hypotheses that must be carefully assessed with further problem-oriented investigations and tests. The first hypothesis is that proto-Japonic and proto-Koreanic had already split (assuming they are genetically related) before they entered the Korean Peninsula. Both proto-Japonic and proto-Koreanic speakers migrated together to the Korean Peninsula along with the dry farming of rice and formed the Mumun Culture. Later, speakers of proto-Japonic aggregated in southern Korea and developed wet farming as an internal innovation in the southern part of the peninsula (i.e. the Songgukri Culture), and later, migrated to Kyushu, Japan.

The second scenario assumes that before the divergence of proto-Japonic and proto-Koreanic, speakers of the common ancestors of the two languages entered the Korean Peninsula, bringing with them dry farming and rice. The Songgukri Culture newly appeared in southwestern Korea ca. 800 BCE, while populations in central Korea preserved the existing material culture and subsistence economy, resulting in a spatial division that eventually led to the divergence of proto-Japonic and proto-Koreanic. In other words, the language spoken by the southern group developed into proto-Japonic, while the language spoken by the remaining central and northern groups became proto-Koreanic. Around 600 BCE, some of the Songgukri population, the speakers of proto-Japonic, migrated to Kyushu, Japan, bringing with them the proto-Japonic language.

Both scenarios have problems. The first scenario assumes a split between proto-Koreanic and proto-Japonic before their entrance into the Korean Peninsula, but as seen above, Early Mumun material culture and technology were homogenous throughout the peninsula, making it difficult to distinguish the two groups. Meanwhile, the second scenario, which assumes the split between the two languages took place as the Songgukri Culture newly appeared in southern Korea around 800 BCE, does not well explain the linguistic distance between Koreanic and Japonic, which is too great to assume a recent split. In short, while the first scenario is not well supported by the archaeological record, the second is not strong enough from a linguistic perspective.

If interpretations are not restricted by the main premises of the FLDH, more hypotheses about the spread and split of proto-Koreanic and proto-Japonic can be proposed. It is now well known that, before the introduction of rice to Korea, hunter–gatherers of the Korean Chulmun, Japanese Jomon and the Boisman Culture of the Russian Far East maintained regional-scale networks from the seventh to third millennia BCE (Korean Archaeological Society 2010). Also, after the end of the Slender Dagger Period around 100 BCE, Chinese Han commanderies were established in northern Korea and iron was widespread and actively used as agricultural tools and weaponry, facilitating the emergence of various competitive polities, spatial divergence in material culture, a total reorganization of international networks and maybe population distributions (Korean Archaeological Society 2010). We do not argue that these events provide a better hypothesis to explain the spread and divergence of the Koreanic and Japonic languages. Instead, we suggest that there are many alternative factors that may possibly explain the dispersal and divergence of the two languages that do not necessarily rely on the FLDH.