Geography and research background

The Cagayan River is the longest river in the Philippines (Figure 1: 1). From its headwaters in the Caraballo Mountains in central Luzon, it flows northward for 446km to enter the Babuyan Channel. Its basin contains deep alluvial deposits, accumulated from the main river and its various tributaries, totalling approximately 3125km² of Tertiary and Quaternary alluvial fill (Wernstedt & Spencer Reference Wernstedt and Spencer1967: 17 & 314).

Figure 1. 1) The Cagayan River in the Lal-Lo area; 2) part of the Magapit shell midden; 3) archaeological excavation of square P15 at Nagsabaran; 4) the Nagsabaran site, viewed from a distance (photographs by H.C. Hung).

Luzon does not lie on a continental shelf, and therefore its coastlines rise steeply from great offshore depths. During the Last Glacial Maximum (c. 24–18 kya), the rivers of Luzon incised canyons into their lower courses and flowed to meet a sea level that was nearly 120m below its present position. With postglacial sea-level rise, the narrow and steep-sided canyons were flooded, and the Cagayan Valley, in particular, included a sprawling estuary, which extending inland for perhaps 100km from the palaeo-coastline. By 7000 years ago, the rising sea had stabilised to around its current level, and in-washed sediments thereafter created the present-day Cagayan alluvial plain, burying under considerable depths the remains of any previous human settlements, as has been documented previously (Carson & Hung Reference Carson and Hung2018).

Archaeological explorations in the lower Cagayan Valley commenced in May 1971, when Israel Cabanilla and Yoji Aoyagi discovered the Magapit shell midden, located atop a section of the steep eastern bank cut back by the Cagayan River (Cabanilla Reference Cabanilla1972). So far, over 30 shell middens have been reported in the lower Cagayan Valley, making it perhaps the densest landscape of prehistoric settlement in Island Southeast Asia. The large number of middens reflects the unusually rich shellfish resources of the mid-Holocene estuary.

Most of these shell middens are distributed over a distance of 20–30km between the modern towns of Gattaran and Lal-lo. Downstream, to the north of Lal-lo, the alluvium is too recent to contain sites of Neolithic date. All Neolithic sites were previously identified as exposures in the banks of the river, or as mounds with loose shell near to the river. The shell middens comprise thick deposits of kabibe bivalve shell (Batissa childreni), with small quantities of other estuarine gastropod and bivalve species, including Thiara rudis, Thiara winteri, Melanoides tuberculata, Melanoides granifera, Melanoides maculata, Corbicula fluminea and Nitidotellina minuta. Some of the shell middens are more than 5m deep (Figure 1: 2–3), and many overlie basal layers of alluvium containing pottery and other artefacts (Aoyagi et al. Reference Aoyagi1993; Ogawa Reference Ogawa2005; Hung Reference Hung2008).

In addition to the shell middens, there are several caves and open sites in the limestone hills to the east of the Cagayan River, especially in the Peñablanca region. These sites contain cultural sequences from the Preceramic through to the Metal Age, and document continuing interaction between hinterland foragers and riverine agriculturalists, described ethnographically for this region by Jean Peterson (Reference Peterson1978). Callao Cave is the largest and oldest of these sites; excavations here have recovered evidence of Homo luzonensis, a small-bodied hominin species of the Late Pleistocene (Détroit et al. Reference Détroit2019).

Several of the shell middens in the Cagayan Valley contain layers that span variously the Preceramic, Neolithic and Metal Age periods. The Gaerlan shell midden, located on the east bank of the river, 45km upstream from its mouth, for example, includes a lower Preceramic matrix and an upper Neolithic matrix with potsherds (Ogawa Reference Ogawa2005). Other middens near Lal-lo, such as Catugan, Irigayen and Nagsabaran, contain Neolithic and Metal Age layers with no underlying Preceramic layer. At these three sites, the red-slipped, and sometimes incised and stamped Neolithic pottery extends downwards into the alluvium that pre-dates the shell midden. The Metal Age black wares tend to be concentrated in the shell middens themselves (Tanaka Reference Tanaka1998; De la Torre Reference De la Torre2000; Hung Reference Hung2008).

So far, no shell midden has revealed a continuous chronological sequence covering the past 7000 years, but some caves may have preserved longer time spans. For example, investigations of Pintú rockshelter, located 250km south of Lal-lo on the Ngilinan tributary of the Cagayan River in Barrio Cabu'an, Nueva Vizcaya Province, have recovered core and flake stone tools throughout the sequence, with sparse pottery in the middle and upper layers. Two radiocarbon dates from Pintú calibrate to 4960–3683 BP for Preceramic occupation and 4150–2949 BP for the earliest appearance of pottery (Peterson Reference Peterson1974; see Table S1 in the online supplementary material (OSM)), although the error ranges are broad. The pottery at Pintú is described as a “reddish-orange ware” (Peterson Reference Peterson1974: 29), with some rims showing stamped circles on their interiors, resembling the Neolithic red-slipped sherds from the Cagayan Valley.

The Preceramic period (7000–4200/4000 BP)

The chronology and cultural content of the Preceramic shell middens is established based on four sites: Ulet, Leodivico Capiña, Miguel Supnet and Gaerlan. Their locations are shown in Figure 2 (1, 2, 6 & 7, respectively), with relevant radiocarbon dates listed in Table S1. These sites are located on islets of slightly raised alluvium or on promontories close to the mouth of a Cagayan estuary that, at 7000–4200/4000 BP, was much broader than it is now.

Figure 2. The major archaeological sites discussed in this study and landscape changes through time in the lower Cagayan Valley: 1) Ulet; 2) Leodivico Capiña; 3) Callao Cave; 4) Musang Cave; 5) Arku Cave; 6) Miguel Supnet; 7) Gaerlan; 8) Nagsabaran; 9) Irigayen; 10) Magapit; 11) Pamittan; 12) Andarayan. This figure uses an ancient landscape model refined by Carson and Hung (Reference Carson and Hung2018) (figure credit: M.T. Carson).

Of these four Preceramic shell middens, Ulet yielded stone flakes but no pottery during augering in 1986, with an associated date of 6745–6495 cal BP obtained from charcoal (Ogawa & Aguilera, Jr. Reference Ogawa and Aguilera1992). Gaerlan has a lower Preceramic layer with chert and andesite flakes, dated to 4295–4090 cal BP from animal bone (Table S1: NUTA2-7941). The upper layer with red-slipped pottery at Gaerlan has three dates that range from 4092–3687 cal BP (Ogawa Reference Ogawa2005).

The Leodivico Capiña and Miguel Supnet middens are located on the west bank of the river. Both comprise 1.5–3m of dense shell midden containing animal bones and flakes of chert. When excavated by Tsang, Santiago and Hung in 1998, these sites were regarded as Neolithic. Both middens, however, lack pottery below their topsoil, as well as the polished stone tools, baked clay spindle whorls and body ornaments that now are understood to be indicators of regional Neolithic assemblages (Tanaka Reference Tanaka2002; Hung Reference Hung2005, Reference Hung2008; Ogawa Reference Ogawa2005). Excavation square P1 at Leodivico Capiña, for example, yielded 39.5g of pottery from the upper 0.30m of a 4 × 4m trench that was 3.2m in overall depth; no pottery was found below this level. A similar situation was recorded at Miguel Supnet. In total, 20 radiocarbon dates are available for these two sites, based on charcoal, animal bone and riverine shell. The dates fall between 7074 and 4514 cal BP (Figures 3, 4 & 5; Table S1).

Figure 3. Radiocarbon dates on charcoal, bone and crop remains from all sites discussed in the Cagayan Valley. Riverine shell dates are excluded here owing to uncertain limestone effects but see Table S1 in the online supplementary material (OSM). The dates have been calibrated in a Bayesian model incorporating phasing (Bronk Ramsey Reference Bronk Ramsey2009), using OxCal v4.4.4, with IntCal20 (Reimer et al. Reference Reimer2020).

Figure 4. North, east, west and south profiles of square P1 at Leodivico Capiña shell midden, with the locations of three radiocarbon dates on charcoal (GX-241112, 241114 and 241119) (figure credit: H.C. Hung).

Figure 5. North and east profiles of square P2 at Miguel Supnet shell midden, with the locations of two radiocarbon dates on pig bone, unidentified to species (S-ANU 66805 and 66806). A wild pig species, Sus philippensis, is endemic to the Philippines (figure credit: H.C. Hung).

The faunal remains previously recovered from the Preceramic deposits at Leodivico Capiña and Miguel Supnet include wild pig (probably Sus philippensis), deer, rat and bird, together with riverine shellfish, fish and turtle (Tsang et al. Reference Tsang2002). The botanical macro-remains recovered from Leodivico Capiña and Miguel Supnet in 1998 suggest a presence of tubers and nuts, probably including wild yam, but no evidence was found for cereals, such as rice or millet (Paz Reference Paz2001).

In Southeast Asia, pre-Neolithic coastal and riverine shell midden sites dated to between >7000 and 4500 cal BP are reported from Vietnam, Thailand, Peninsular Malaysia, Sumatra, Sulawesi, Mindanao and southern China (Figure 6) (e.g. Van Stein Callenfels Reference Van Stein Callenfels1936; Ha Reference Ha1996; Bolunia Reference Bolunia2005; Zhang & Hung Reference Zhang and Hung2012, Reference Zhang and Hung2016; Higham Reference Higham2014; Bellwood Reference Bellwood2017; Hung Reference Hung2019; Hung & Zhang Reference Hung, Zhang, Wu and Rolett2019). Many were created by foragers of Australo-Papuan skeletal affinity (Matsumura et al. Reference Matsumura2019), and many in northern Vietnam and southern China contained pottery, although neither pottery nor human remains have yet been recovered from the Preceramic middens in the Cagayan Valley.

Figure 6. The location of the study area (lower Cagayan Valley, North Luzon), and the locations of representative (pre-farming) shell middens in southern China and Southeast Asia during the Middle Holocene, c. 7000–4500 years BP (figure credit: CartoGIS Services, ANU Scholarly Information Services, The Australian National University).

The Neolithic period (4200/4000–2400 BP)

The Neolithic of the Cagayan Valley saw the introduction of a new assemblage that included pottery, baked clay spindle whorls, polished stone adzes, bark-cloth beaters and body ornaments. The latter include penannular ear pendants, bracelets and beads that were variously made of shell, baked clay, quartz schist and semi-precious stones, including Taiwan nephrite (jade) from the Fengtian source near Hualian, eastern Taiwan. Small numbers of chert flakes appear occasionally in these Neolithic assemblages, but most functional stone tools appear to have been wholly polished (Ogawa Reference Ogawa2005; Hung Reference Hung2008) (Figure 7: 13–23).

Figure 7. Nagsabaran Metal Age Indo-Pacific glass beads (1), bronze bell-shaped ornaments (2), iron knife (3) and black pottery (4–12); Neolithic red-slipped pottery (13–14), clay spindle whorls (15–16), clay object (17), flaked chert (18–19), polished andesite adze (20), tuffaceous sandstone stepped-adze preform (21), green quartz schist beads (22) and Taiwan nephrite bracelet fragment (23) (scales in cm) (photographs by H.C. Hung).

According to the available radiocarbon dates, the Cagayan Neolithic began c. 4200–4000 BP (Figure 3; Table S1). This dating is coeval with that of the related cultural horizon in the Batanes Islands to the north of Luzon (Bellwood & Dizon Reference Bellwood and Dizon2013). From a linguistic perspective, the Batanes Islands and Luzon were settled at around the same time by people of a shared language community (Ross Reference Ross2005; Blust Reference Blust2019). While this migration apparently brought the first people ever to live in the Batanes (based on current evidence), it also introduced an overlay of people into the already-inhabited land mass of Luzon.

The Neolithic assemblages from Nagsabaran and Magapit (Figure 1: 2–4; Figure 2: locations 8 & 10) contain bones of domestic pigs (directly radiocarbon dated to 4448–4246 cal BP at Nagsabaran; see Hung Reference Hung2008; Piper et al. Reference Piper2009) and macro-botanical remains of rice (Oryza sativa) and Job's tears (Coix lacryma-jobi). The Neolithic layer of Nagsabaran yielded 79 rice grains and fragments, as well as 224 grains and fragments of Job's tears, from a 4 × 4m trench excavated by Hung, Bolunia, Carson and Deng in 2016 (Figure 8). Foxtail millet (Setaria italica) then made an appearance in the Metal Age layers. Similar evidence was recovered at Magapit in 2015, where rice spikelet bases with domesticated-type abscission scars were identified in our preliminary study (Figure 9). One carbonised rice grain from the Magapit profile has been directly radiocarbon dated to c. 3200–3000 cal BP (Beta-416880), but the lower stratigraphy in this site has not yet been exposed. In addition, the Neolithic layer of Magapit has produced possible banana phytoliths (Musa sp.), the domestication status of which is unknown.

Figure 8. South and west profiles of square P15 at Nagsabaran, with six radiocarbon dates, comprising UGAMS-27088 and UGAMS-27091 on Job's tear (Coix lacryma-jobi) grains; UGAMS-27089, UGAMS-27090, and Beta-437271 on rice (Oryza sativa) grains; and Beta-436818 on charcoal (figure credit: H.C. Hung).

Figure 9. Plant remains from Nagsabaran (a–c) and Magapit (d–f): a & d) rice (Oryza sativa) grains; b) foxtail millet (Setaria italica) grain; c) Job's tear (Coix lacryma-jobi) grain; e) rice spikelet base; f) phytolith of cf. Musa sp.; item (b) is Metal Age, while all others are from Neolithic layers (figure credit: Z. Deng).

Recently, archaeobotanical evidence for Neolithic mixed rice and millet agriculture has been recovered in adjacent regions, associated with dates of 4600–4800 cal BP, at Gancaoling, in the Pearl River Delta of coastal Guangdong (Deng et al. Reference Deng2022), and >4500 cal BP at Nanguanlidong, in southern Taiwan (Tsang et al. Reference Tsang2017).

Approximately 80km south of Magapit, the Neolithic site of Andarayan (Figure 2: location 12) has also produced red-slipped pottery with an AMS date of 3935–3378 cal BP from a rice husk inclusion, together with another charcoal date of 3890–3060 cal BP (Snow et al. Reference Snow1986). A macro-botanical presence of rice is therefore now attested at three Neolithic sites in the Cagayan Valley (Nagsabaran, Magapit and Andarayan), although there was less available lowland, alluvial farmland at that time (Carson & Hung Reference Carson and Hung2018) (Figure 2: lower left).

Two major characteristics of the oldest Neolithic pottery in the Cagayan Valley are the use of a sand temper and a distinctive red slip (Aoyagi et al. Reference Aoyagi1993; Hung Reference Hung2008) (Figure 10). These attributes are paralleled closely in the red-slipped pottery from Andarayan, and from the sites of Chaolaiqiao (4200 cal BP) in south-eastern Taiwan (Hung Reference Hung2005, Reference Hung2008) and Minanga Sipakko in West Sulawesi (3500–3200 cal BP; Anggraeni et al. Reference Anggraeni, Simanjuntak, Bellwood and Piper2014). Both Chaolaiqiao and Minanga Sipakko have also yielded plentiful rice phytoliths (Deng et al. Reference Deng2018, Reference Deng2020) (Figure 10: 6 & 15). Furthermore, a red-slipped pottery assemblage with the same rim forms and vessel shapes as those in the Cagayan sites has been radiocarbon dated via associated charcoal to 3560–3380 cal BP at Yinian, in south-eastern Hainan Island (Wang et al. Reference Wang, Li, Jia and Han2016) (Figure 10: 11–12). Notably, Hainan has never been considered as part of the Austronesian expansion during its Neolithic phase. Tsat is descended from a population that fled from Vietnam to Hainan after the fall of the northern Cham capital to the Vietnamese in AD 982 (Blust Reference Blust2019). Today, the Hlai people in Hainan still speak Kra-Dai (Tai-Kadai) languages, which are part of a family considered by several linguists (e.g. Ostapirat Reference Ostapirat, Sagart, Blench and Sanchez-Mazas2005; Sagart Reference Sagart, Sagart, Blench and Sanchez-Mazas2005) to be distantly related to Austronesian, and especially Malayo-Polynesian languages in Island Southeast Asia, thus suggesting the probability of ancient contact.

Figure 10. Red-slipped pottery (1–5, 7–9 & 11–14) and associated rice (Oryza sativa remains (6 & 15: phytoliths; 10: grain) from Chaolaiqiao, Nagsabaran, Yinian and Minanga Sipakko. Incised and impressed red-slipped pottery from Magapit: 16) open-mouthed pot on a pedestal, shown upside-down to reveal the stamped circles and possible fingernail impression decoration; 17) punctate-stamped sherd with lime or white clay infill in decoration; 18) sherd also displaying traces of white infill in incised lozenge motif with punctate infilling and impressed circles. Similarly decorated, red-slipped pottery from Nagsabaran (19–20) and Xom Ren (26–30 but without red slip). Baked clay earrings from Nagsabaran (21–25) and similar from Thach Lac (31–34). Sources: 11) Wang et al. Reference Wang, Li, Jia and Han2016: 119; 13) Anggraeni et al. Reference Anggraeni, Simanjuntak, Bellwood and Piper2014: 745 (both reproduced with permission); 6, 10 & 15) photographs by Z. Deng; 16–18) photographs by P. Bellwood, courtesy of K. Tanaka; 1–5, 7–9, 12, 14 & 19–34) photographs by H.C. Hung).

In the Cagayan sites, 1 per cent or less of all red-slipped pottery fragments have fine incised and impressed decoration that includes pointillé (or punctate) stamped geometric motifs, created from rows of small, round and pointed impressions interspersed with stamped circles, and sometimes organised within fields outlined by incised lines. This type of decoration is well represented in Nagsabaran and Magapit (Figure 10: 16–20). Most of this stamped decoration occurs on rims, carinated shoulders and ring feet, forming straight or zig-zag lines and geometric patterns. Punctuate decoration in the Cagayan Valley suggests the use of a toothed, comb-like tool, and the impressions often retain traces of white lime or white clay infill.

At Gaerlan, Irigayen, Nagsabaran and Magapit, the layers containing red-slipped earthenware include both decorated and undecorated sherds, and a definitive starting date has been difficult to ascertain for the decorated pottery. Our current estimate, based on available radiocarbon dates and stratigraphic contexts, is c. 3700–3500 cal BP. From a broader geographical perspective, similar incised and impressed decoration with lime infill also occurs at Neolithic sites in northern Vietnam, such as Man Bac and Xom Ren (Figure 10: 26–30), where it is dated to between 3900 and 3500 cal BP. Vessel forms and rim shapes here, however, are significantly different from those in Luzon, and have little of the diagnostic red slip that dominates in Island Southeast Asia and Oceania (Khan Reference Khan2009; Nguyen et al. Reference Nguyen, Yamagata, Watanabe, Bellwood, Oxenham, Matsumura and Nguyen2011). At the same time, specific forms of baked clay earring also suggest possible cultural contacts between northern Luzon and northern Vietnam—especially globular or flattened globular earrings. There are also a number of ring-shaped items (usually partly damaged, having lost their hooks) from the Cagayan sites (Figure 10: 21–25) that resemble similar items from sites such as Thach Lac in north-central Vietnam (Figure 10: 31–34).

The beginning of the Metal Age, c. 2400 BP

At many of the Cagayan Valley midden sites, the layers containing Neolithic red-slipped pottery are overlain by layers with black-surfaced pottery (Ogawa Reference Ogawa2005; Tsang Reference Tsang, Chiu and Sand2007; Hung Reference Hung2008). Ethnographic observations suggest that the black surface colour results from firing in an oxygen-deprived environment, perhaps beneath rice husks. Associated with the black pottery are objects of iron, such as knives, and of cupreous metal, such as small bronze ornaments. There are also many monochrome glass beads (Hung Reference Hung2008; Bellwood Reference Bellwood2017) (Figure 7: 1–12). The sources of these Metal Age artefacts have not been determined, but previous research has suggested that most of the Indo-Pacific glass beads (see Figure 7: 1) were imported from South Asia or Mainland Southeast Asia (unpublished data analysed by Yoshiyuki Iizuka in 2005).

Although most Metal Age vessel forms are distinct from those of the red-slipped Neolithic pottery, a transitional range from one to the other has been observed within the continuous stratigraphic sequences at Magapit and Nagsabaran. Additionally, aDNA studies of Metal Age skeletons from Nagsabaran confirm a close genetic link with modern Amis (Ami) people in eastern Taiwan (McColl et al. Reference McColl2018). Because of the apparent continuity in the archaeological record through time, this link is consistent with expectations of genetic continuity rather than population replacement in the Cagayan Valley after the commencement of the Neolithic. No aDNA, however, has so far been recovered from Cagayan skeletons of Neolithic date.