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Journal of Archaeological Science 61 (2015) 149e157

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Journal of Archaeological Science

journal homepage: http : / /www.elsevier .com/locate/ jas

Mobility of early islanders in the Philippines during the TerminalPleistocene/Early Holocene boundary: pXRF-analysis of obsidianartefacts

Leee Anthony M. Neri a, Alfred F. Pawlik a, *, Christian Reepmeyer b,Armand Salvador B. Mijares a, Victor J. Paz a

a University of the Philippines, Archaeological Studies Program, Albert Hall, Diliman, Quezon City 1101, Philippinesb James Cook University, College of Arts, Society and Education, Cairns QLD, Australia

a r t i c l e i n f o

Article history:Received 10 June 2014Received in revised form14 May 2015Accepted 16 May 2015Available online 2 June 2015

Keywords:Obsidian sourcingPXRFHuman migrationMaritime interactionPleistocene/Holocene boundaryIsland Southeast AsiaPhilippines

* Corresponding author.E-mail addresses: afpawlik@gmail.com, afpawlik@

http://dx.doi.org/10.1016/j.jas.2015.05.0050305-4403/© 2015 Published by Elsevier Ltd.

a b s t r a c t

The Philippine archipelago spans over two distinct biogeographic zones, Sundaland and Wallacea. Wereport in this paper on finds from Ilin Island just off the coast of SW-Mindoro, and El Nido in NorthernPalawan. While the island of Palawan is linked to Sundaland, Mindoro and Ilin Island belong to Wallacea,east of Huxley's Line. Ongoing archaeological investigations at Bubog 1 Rockshelter on Ilin Island and IlleCave & Rockshelter in northern Palawan, delivered obsidian artefacts, found in Terminal Pleistocene andEarly Holocene layers. PXRF analysis of the obsidian samples from Mindoro and Palawan shows that theywere coming from the same, yet unknown source. They clearly indicate that the two distinct paleo-geographical regions were linked to each other, suggesting human interaction and maritime networks asearly as ca. 12ka BP. The results of this study contribute substantially to our understanding of the mobilityof early islanders during the Terminal Pleistocene and the processes of human island adaptation andenhance our current knowledge of subsistence strategies across the region.

© 2015 Published by Elsevier Ltd.

1. Introduction

The nature of maritime interaction in the pre-Neolithic period(before ~4500 years ago) is a key issue in Indo-Pacific prehistoryand to the global debate about process and significance of Neolithictransformation. In Island Southeast Asia (ISEA), however, pastresearch focused dominantly on the hypothesis of migration ofagriculturally and technologically advanced ‘Austronesian’ groupsfrom Taiwan into the Pacific, the ‘Austronesian’ Neolithic expansion(Bellwood, 1997, 2011). Increasingly, new data indicate the impor-tance of economic and ecologic changes in pre-Neolithic societiesduring the early to mid-Holocene (Barker and Richards, 2013;Bulbeck, 2008; Donohue and Denham, 2010; Pawlik et al. 2014,2015). These new results suggest that the period of the TerminalPleistocene (before 12,000 years ago) to the mid-Holocene (around6000 years ago) is central to understanding the complex interplay

up.edu.ph (A.F. Pawlik).

of migration, adaptation and integration of innovations and pop-ulations (Barker and Richards, 2013; Soares et al., 2008, 2011).

Early open water crossing in ISEA by modern humans 50,000years ago is evident in the permanent colonization of Sahul(Australia and New Guinea) (O'Connor, 2010) and maybe evenearlier on theWallacean islands of the Philippines, including Luzon,Mindoro, the Visayas and Mindanao (Heaney, 1993; Esselstyn et al.,2010; Porr et al., 2012; Pawlik et al., 2014, 2015). Recent excavationsin Callao Cave, northern Luzon have delivered the remains of ahominin directly dated through U-series to a minimum age of66.7 ± 1 ka BP (Mijares et al., 2010), or approx. 50 ka BP respectively(Grün et al., 2014). A posited land bridge either in the UpperPleistocene (Fox, 1970; Earl of Cranbrook, 2000) or more likelyalready in the Middle Pleistocene (Heaney, 1985; Pawlik andRonquillo, 2003; Piper et al., 2008, 2011) helped in the coloniza-tion of the island of Palawan (Fig. 1) by the inhabitants of Sunda-land, possibly including early hominins. Excavations on PalawanIsland produced evidence for the presence of anatomically modernhumans in the Philippines more than 35,000 years ago (Fox, 1970,1978; D�etroit et al., 2004; Dizon, 2003).

Fig. 1. Map of the Philippines showing the locations of relevant sites and possible migration paths into the Wallacean islands of the Philippine archipelago. Identified obsidiansources in Island Southeast Asia in black italic writing.

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In this paper, we present geochemical evidence for maritimeinteraction between the islands of Mindoro and Palawan in thePhilippines, beginning in the Terminal Pleistocene. Mindoro is astrategically located land formation between Borneo/Palawan andthe oceanic Philippine islands that may have served as a stepping-stone in the colonization of the Philippine archipelago as part of thecentral route via the Sunda Shelf and Borneo to Palawan, thenMindoro into Luzon (Porr et al., 2012; Pawlik et al., 2014) (Fig. 1).Mindoro was never connected to the Southeast Asian mainlandduring the Pleistocene, and like other Philippine islands it containsa rich endemic island fauna (Heaney et al., 2011; Pawlik et al., 2014;Reyes et al., in review). However, while the islands of Palawan andLuzon have already produced some of the earliest evidence formodern human occupation in ISEA (Fox, 1970; Mijares et al., 2010;Pawlik and Ronquillo, 2003; Paz, 2004), Mindoro has remained anarchaeological mystery with respect to early human colonizationand adaptation until very recently.

The reconstruction of the mobility patterns of people is usuallylimited by scarce archaeological evidence. Linking raw materialsback to sources is a way to track the area over which people mayhave traveled. Due to their durability, lithic artefacts are especiallysuited for such a provenance study. Here, we apply geochemicalcharacterization of obsidian materials recovered from Bubog 1Rockshelter on Ilin Island, an off-shore island of Mindoro, and IlleCave on Palawan (Fig. 1) by means of portable X-ray fluorescencespectrometry (pXRF). We will utilize the data to reconstruct rawmaterial procurement strategies and mobility patterns at thetransition of the Terminal Pleistocene to the Early Holocene.

2. Archaeological sites

2.1. Ille Cave and Rockshelter

Ille Cave is located in the karstic Ille limestone tower in theDewil Valley, New Ibajay in the municipality of El Nido, PalawanProvince, northeast of the island of Palawan (Hara and Cayron,2001; Lewis et al., 2008). The formation belongs to the PermianNorth Palawan Block, (Kiessling and Flügel, 2000). The excavationat Ille is part of the Palawan Island Palaeohistoric Research Project

conducted by the Archaeological Studies Program (ASP), Universityof the Philippines and the National Museum of the Philippines thatstarted in 1998. Several obsidian flakes together with artefactsmade of chert, charcoal, burnt and unburnt animal bones and shellswere recovered from the ‘East Mouth Excavation’ in the rockshelterarea of Ille and associated with a series of AMS 14C dates oncharcoal ranging between ca. 9500e11,000 cal. BP (Lewis et al.,2008: 320, Fig. 2; Robles et al. 2015).

Most obsidian artefacts are fragments of smaller flakes andmicroblades (Table 1). Prepared platform remnants and a dorsalreduction on the proximal fragments indicate core preparation.Bipolar core reduction is observed in at least one case. Three of thestudied obsidian artefacts appear to have use traces. A microbladefragment shows slight edge scarring while a fragment of a smallflake exhibits edge scarring on one lateral edge and rounding on theopposite edge. The largest obsidian artefact can be morphologicallyclassified as a so-called pi�ece �esquill�ee, made of an angular flake of23.1 mm length with heavily shattered and reduced ends that wasprobably used as chisel-like instrument on harder material.

2.2. Bubog 1 Rockshelter

Bubog 1 Rockshelter site in Sitio Bubog, Barangay Pawikan, IlinIsland, San Jose, Occidental Mindoro, is located just off the SW sideofMindoro (Porr et al., 2012; Pawlik et al., 2014). At present, Ilin andMindoro are separated by a ca. 900e1300 mwide channel. Bubog 1is located near the south-eastern end of the island at ca. 30 m abovemean sea level.

Ongoing excavations since 2011 produced a ca. 140 cm deep,well-stratified shell midden. This midden sequence reflects thepalaeoenvironmental history and changing landscapes betweenIlin Island and Mindoro from lakes and mangrove swamp duringlow sea levels at the end of the last glaciation through shallow,intertidal marine environments to the development of ‘mature’lagoon conditions by the later Holocene (Pawlik et al. 2014). Ninedistinctive layers of midden deposition have been identified andare anchored to an absolute chronology by several radiocarbondates (Fig. 2).

Fig. 2. The conjoined south wall profile of Bubog 1, Trench 1e2.

L.A.M. Neri et al. / Journal of Archaeological Science 61 (2015) 149e157 151

The upper three layers of the shell midden sequence weredisturbed by treasure hunters and contained seven undecoratedpotsherds. Considering the earliest securely dated appearance ofpottery in the Philippines, the finds suggest a formation of thelayers after ca. 4000 cal. BP (Spriggs, 2003, 2011; Mijares, 2007;Pawlik et al., 2014). This is in accordance with a radiocarbon dateon charcoal from Layer 4 of 4240e4081 cal BP (S-ANU 32037). AConus sp. shell from Layer 5 produced a date of 5891e5525 cal BP(WK-32984). A shell adze was recovered from Layer 8 and directlyAMS-dated to an age of 7550e7250 cal BP (S-ANU-35132) (Pawliket al., 2015). A fragment of a charred Canarium hirsutum nut fromLayer 9 at the base of the shell midden sequence produced an age of11,099e10,761 cal BP (WK-32983) for the initial stage of shellmidden deposition. By the end of 2014, excavation has reached adepth of ca. 200 cm below the shell midden, and another threecultural stratigraphic layers have been exposed underneath the

Table 1The analyzed obsidian artefacts from Ille Cave and Bubog 1 Rockshelter showing basic attmillion (ppm).5

shell deposits. They are composed of a silty, homogenous sedimentof possibly aeolian origin. Among the retrieved cultural materialswere few flaked artefacts and the remains of an endemic terrestrialfauna, including Tamaraw (Bubalus mindorensis), wild pig, lizardsand murids, together with the remains of reef and pelagic fishes.Radiometric dating is still ongoing but this context can be tenta-tively attributed to the final stage of the Terminal Pleistocene andbefore ca. 11ka cal. BP.

Five small obsidian artefacts were retrieved from the lowestLayer 9 of the shell midden. Twomore, equally small obsidian flakeswere recovered from the “terrestrial” Layer 10, about 20 cm and50 cm below the deepest shell midden layer. All obsidians arerather small with maximum sizes below 10 mm and probablymostly debris from the process of tool production (Table 1). Exceptfor an angular shatter all are microflakes and fragments thereofwithout secondary modifications. Traces of use are mostly absent.

ributes and the PXRF analysis of trace elements. All elemental values are in part per

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Only no. IV-2011-G3-890, a distal fragment of a possiblemicrobladefrom Layer 10 shows some scarring on both sides of one lateral edgethat might be use-related and caused by an activity performed inlongitudinal motion.

3. Obsidian characterization using portable X-rayfluorescence spectrometry (PXRF)

The obsidian artefacts from Ille and Bubog 1 were geochemicallyanalyzed with a Bruker AXS Tracer IIIeV portable XRF spectrometer(see Nazaroff et al., 2010; Sheppard et al., 2010; Torrence et al.,2013; Frahm, 2014). This instrument is equipped with an X-raytube employing a rhodium target and a thermoelectrically cooledsilicon PIN detector. The spectrometer was operated at 40 keV and20 mA, with a 180 s count time, a manufactory recommended filter(‘green’ filter) of 6 mil copper (Cu), 1 mil titanium (Ti), and 12 milAluminum (Al) was introduced into the X-ray path (cf. Galipaudet al., 2014). Eleven elements were analyzed: Mn (manganese), Fe(iron), Zn (zinc), Ga (gallium), Th (thorium), Rb (rubidium), Sr(strontium), Y (yttrium), Zr (zirconium) and Nb (niobium). Toensure the accuracy and precision of the instrument used in thisstudy a calibration encompassing the defined concentration stan-dard of the Sierra de Pachuca published standards (Glascock, 1999)and the WNB 4209/Kutau-Bao geological source were used (Birdet al., 1997). Five obsidian artefacts from Ille Cave and sevenobsidian flakes found in Bubog 1 were analyzed (Table 1; Fig. 3). Allartefacts are extremely small and do not full-fill requirements ofinfinite thickness which will increase elemental variance (Lundbladet al., 2008), however, differences in Mn, Fe and Sr values appearnot to be correlated to artefact size (r2 0.0003e0.13, p 0.21e0.23).

The geochemical results indicate two different but inter-relatedraw material outcrops being utilized at the sites. One group,including six artefacts from the Bubog 1 site and two artefacts fromthe Ille site, show slightly higher Mn (m 1044 ppm, SD 124.9), Fe (m45,368 ppm, SD 5325) and Sr (m 215 ppm, SD 25.5) values, with thesecond group showingMn (m 638 ppm, SD 116.8), Fe (m 34,517 ppm,

Fig. 3. A) Obsidian artefacts from Ille Cave

SD 3400) and Sr (m 171 ppm, SD 12.1) respectively. The secondoutcrop was mainly utilized at Ille, only one artefact was recoveredfrom Bubog 1. Both groups show medium range Nb values (m18 ppm, SD 5.1) outside of common Island Arc deriving lavas and arelative unusual Rb/Sr ratio of 0.44e0.64 for obsidian sources inISEA and the Pacific (Reepmeyer et al., 2011b).

Consequently, the next step is to identify the geological sourceof the obsidian artefacts from Ille and Bubog 1. Most obsidianprovenance studies are based on numerous source samples and theartefact data can be compared to the source compositions todetermine source assignments (e.g. Eerkens et al., 2007; Shackley,2005; Tykot, 2003; Torrence et al., 1992). Despite the fact that thePhilippine archipelago is mostly volcanic in nature with more than200 known volcanoes, 22 of these being considered active(PHIVOLCS, 1997:1e78), only one primary obsidian source has beenidentified in the Philippines, the Nagcarlan source, located in Bar-angay Manaol, Province of Laguna (Neri, 2003, 2007). The source issituated on top of a hill, ca. 40 m above sea level and some obsidiannodules eroded towards the plunks of Mt. Nagcarlan. This source isprobably the result of an explosive volcanic eruption, associatedwith quaternary volcanism in the Laguna region that producedpyroclastic material (Bureau of Mines, 2000:2). The outcrops areexposed along the volcanic plugs associated with tuffaceous andpyroclastic rocks occupying the lower ridges of Mt. Nagcarlan. Thevolcanic glass only shows some minute inclusions of crystallitesand amygdules of quartz and zeolites (Bureau of Mines, 1968: 309).It is mostly cobble to boulder sized and dark in color and containselongated or rounded bubbles. It is opaque to transparent andisotropic with a refractive index of 1.48e1.52. The hardness rangesfrom 5 to 5.5 on the Mohs scale and the specific gravity varies from2.33 to 2.50 depending on the abundance of vesicles. Nagcarlanobsidian was exploited by settlers from nearby sites in Batangasand Laguna at the least starting from the 10th century AD (Neri andde la Torre, 2007; Paz et al., 2013). However, no earlier, Neolithicand pre-Neolithic use of this obsidian is known so far. Thirty-fivesamples of the Nagcarlan obsidian were analyzed by pXRF with

; B) Obsidian artefacts from Bubog 1.

Table 2Trace elements of the Nagcarlan source and archaeological sites analysed by pXRF. All elemental values are in parts per million (ppm). Obsidian reference standards aspublished in Reepmeyer et al. (2011b), Glascock and Ferguson (2012).

Trace element concentration in ppm

Sample Name Mn Fe Zn Ga Th Rb Sr Y Zr NbGeological SourceNAGCARLAN (n ¼ 35)Mean 593 11,365 50 18 13 135 92 36 201 11S.D. 77.4 1284.3 8.7 2.0 2.2 5.4 8.3 1.8 15.7 1.1Archaeological SitesGroup 1 (n ¼ 8)Mean 1044 45,368 77 18 12 112 215 30 274 19S.D. 124.9 5325.8 66.9 3.0 2.3 9.7 25.5 1.3 14.8 5.8Group 2 (n ¼ 4)Mean 638 34,517 68 16 12 99 171 29 254 18S.D. 116.8 3400.8 26.4 1.2 3.6 11.5 12.1 2.8 22.9 4.2Int. reference materialANU9000 e Kutau/Bao source, West New Britain (n ¼ 20)Mean 482 8652 16 3 55 238 21 138 2S.D. 35.9 358.8 1.2 1.0 3.0 6.6 1.0 3.2 0.6Preferred values 448 7247 3 52 206 19 127 3S.D. 25.7 2213.2 0.3 1.2 46.6 2.3 10.1 0.5

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identical instrument settings (Table 2). The elemental range of theNagcarlan obsidian was plotted in a ternary diagram of the ele-ments Zr, Rb, and Sr (Fig. 4) indicating homogeneity of the Nag-carlan obsidian.

The distribution elements analyzed with pXRF were exploredwith multi-variate statistics employing Principal ComponentAnalysis (PCA) in JMP software. An unsupervised method waschosen because of the known incomplete reference dataset for ISEAobsidian sources (Reepmeyer et al., 2011b). Two separate analyseswere conducted first against a pXRF dataset of the Australian Na-tional University reference collection of Western Pacific obsidiansources, including the Nagcarlan source, and in a second stepagainst a wider dataset of Philippine and Indonesian obsidiansources and artefacts including SEM-EDXA and LA-ICP-MS datapreviously published (Reepmeyer et al., 2011b).

Principal Component Analysis of the pXRF dataset shows clearseparation of two groups of artefacts described above (Fig. 5);however, none of the groups matched either the Nagcarlan sourcein south-central Luzon, or any of the known Western Pacificobsidian sources. Further PCA analysis including Indonesian andPhilippine artefacts doesn't unambiguously identify a source (Table3), but shows striking similarities between the geochemical com-positions of artefacts from Cebu (Reepmeyer et al., 2011b) withartefacts from Ille Cave on Palawan and Bubog 1 on Ilin Island(Fig. 6). Unfortunately, artefacts from Cebu are currently undated,but this result might indicate that there was an established

Table 3Comparative data from the Philippines and Indonesia using PXRF and ICPMS respectively

Archaeological sites Obsidian source

Group 1 Group 2 Bandaneira*

Banda Islands

n ¼ 8 n ¼ 4 n ¼ 7

Elements Mean SD Mean SD Mean

Mn 1044 1249 638 1168 1440Th 12 2.3 12 3.6 2.9Rb 112 9.7 99 11.5 28.5Sr 215 25.5 171 12.1 146.4Y 30 1.3 29 2.8 51Zr 274 14.8 254 22.9 144.3Nb 19 5.8 18 4.2 3.4

maritime interaction zone including sites on Palawan, Mindoro andCebu.

4. Discussion

The results of our analysis showed that the people who uti-litzed Ille Cave in northern Palawan and from Bubog 1 Rock-shelter in southern Mindoro accessed and exploited the sameobsidian source. Due to a non-volcanic genesis of Palawan, andsince no obsidian has so far been reported from the islands ofMindoro or Ilin we can conjecture that it is highly likely that theobsidian was not acquired locally but transported over longerdistances to the sites from an off-island source (Neri, 2006;Reepmeyer et al., 2011b). Unfortunately, multi-variate statisticalanalysis of geochemical signatures with the obsidian source atNagcarlan showed no match. A further geochemical comparisonwith known obsidian sources in Indonesia, [Bandaneira, Paso,Nagrek (A & B), and Tapus] (Reepmeyer et al., 2011b) as the nextnearest sources (Table 2), as well as the Western Pacific sources,was conducted. They showed significantly different geochem-istry excluding all of them as possible provenance for the Ille andBubog 1 specimen. This clearly indicates that the Ilin/Bubogobsidian did not come from any of the identified obsidian sour-ces in Indonesia but was acquired from a currently unknownsource. This is not surprising considering the lack of knowledgeof obsidian sources in Island Southeast Asia (Reepmeyer et al.,

(Reepmeyer et al., 2011b*). Trace element concentrations in part per million (ppm).

s in Indonesia

Paso* Nagrek (A)* Nagrek (B)* Tapus*

Sulawesi Java Java Sumatra

n ¼ 1 n ¼ 6 n ¼ 1 n ¼ 1

SD Mean Mean SD Mean Mean

59 519 234 6 233 3070.2 5.8 21.6 0.3 19.3 15.12.2 81.3 187.2 5.4 170.6 136.77.9 71.4 29.6 0.6 46.9 67.12.2 39.3 37.6 0.4 31.9 20.29.9 203.7 96.4 1.1 141.7 71.40.2 5.8 7.5 0.1 7.1 5.6

Fig. 4. Ternary diagram of Rb, Sr, Zr showing internal variation of Nagcarlan source.

L.A.M. Neri et al. / Journal of Archaeological Science 61 (2015) 149e157154

2011b). An alternative scenario of a formerly exposed obsidiansource now submerged (see Torrence et al., 2004; Adams andWyckoff, 1971) seems unlikely, as the surface artefacts foundon Cebu might indicate that the obsidian source was accessibleduring the whole of the Holocene.

The occurrence of obsidian artefacts at both sites in the TerminalPleistocene and Early Holocene coincides with sea-level rise(Lambeck and Chappell, 2001, Hanebuth et al., 2000) changing the

Fig. 5. Principal Component Analysis of pXRF data. representing analyzed artefacts, N(Admiralty Islands), A (West Fergusson), ◊ (East Fergusson).

coastline at the Ille Cave from ~60 km distance during LGM to~30 km at 11,000 years ago to only ~2 km distance at 5000 years ago(Fig. 7); most significant coastal changes on Palawan occur beforethe initial inhabitation of the Ille Cave at 11,000 cal. BP (Lewis et al.,2008). Although Ilin Island was connected to Mindoro during LGMand until ca. 10,000 cal. BP, the distance from Bubog I to the nearestshore in the southern area was about ~1.5 km at 18,000 years agoand not more than ~500 m at 11,000 cal. BP (Pawlik et al., 2014).

Straight line distance between the two archaeological sites isapprox. 210 km; associated with changing sea-level distance to becovered by boat increasing from around 50 km to almost 200 km,although open ocean crossing increased only from 40 km to 80 km.It has been argued that the changing coastlines accompanied by asignificant loss of landmass during this period would have putestablished populations under enormous pressures to adapt a morecoastal and maritime focused economy (Barker and Richards, 2013,Soares et al., 2008). However, the research at Bubog 1, and probablysimilar caves and rock shelters in the area has demonstrated thathuman populations managed to adapt fairly readily to changes inclimate and environment that occurred at the end of the Pleisto-cene (Pawlik et al. 2014; Mijares, 2015; Reyes et al., in review). Thedeposits of the densely packed shell midden at Bubog 1, consistingof high amounts of palatable largemarine gastropods togetherwithaquatic and terrestrial vertebrate bones (Pawlik et al., 2014, 2015;Lim, 2015; Vallejo et al., in prep.), demonstrate that these pop-ulations were quite successful in adapting their foraging strategiesin respect to the dramatic changes that occurred at the end of thePleistocene and into the Holocene. Many of the diverse foraging,and perhaps even plant management strategies, utilized

agcarlan source. Reference obsidian dataset is presented as - (West New Britain), ,

Fig. 6. Principal Component Analysis of pXRF data and published SEM-EDXA and LA-ICP-MS data (Reepmeyer et al., 2011b). Reference obsidian source dataset is presented as -

(West New Britain), , (Admiralty Islands),A (West Fergusson), ◊ (East Fergusson), (Indonesian sources). Artefacts from Cebu (B), Ulilang Bundoc (þ), Mindanao Island sites ( ),Indonesian sites (�).

L.A.M. Neri et al. / Journal of Archaeological Science 61 (2015) 149e157 155

throughout most of the Holocene were already in place by the endof the Pleistocene. It appears that local inhabitants simply modifiedpre-existing behaviors to compensate for changes in circumstanceand maintained many technologies and techniques for extracting

Fig. 7. Map of the region with �120 m bathymetric iso-line (dashe

resources from the local environment throughout the Holocene(Bellwood, 2005; Piper et al., 2011; Rabett et al., 2011). At Bubog theexploitation of mollusk resources began at the end of the TerminalPleistocene when the land connection with Mindoro was flooded

d), �48 m bathymetric iso-line (shaded) and current coastline.

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due to the rising sea levels and the formation of a shallow easterncoast began. While the steep southern coast of Ilin Island probablydidn't permit gathering of shells during and after the TerminalPleistocene, the continuing presence of reef and pelagic fish re-mains in the Terminal Pleistocene Layers of Bubog 1 indicates openwater fishing and the use of watercrafts.

Maritime technology allowing access to pelagic fishing groundsand covering distances of open ocean of >90 km has been argued tobe available to Pleistocene hunter-gatherers as early as 40,000years ago (O'Connell et al., 2010; O'Connor et al., 2011). Maritimeraw material transportation in the Terminal Pleistocene and EarlyHolocene in ISEA on the other hand was previously argued only bytechnological and functional comparison of artefacts (Bulbeck,2008; Bellwood, 1997). The procurement of off-island obsidianraw material, albeit only in very small numbers, might indicate anincreased maritime focus of communities in these now coastalshelters and might suggest an expansion of settlement as early asthe Terminal Pleistocene/Early Holocene boundary (Barker andRichards, 2013). However, if we assume that many of the behav-ioral adaptations to changing environments were already in placeby the Terminal Pleistocene/Early Holocene boundary, there is noreason to deny that maritime raw material transportation was alsoalready established at this time (cf. Reepmeyer et al., 2011a;Summerhayes and Allen, 1993); the lack of obsidian in earlier de-posits therefore might only reflect on utilization patterns ofobsidian artefacts restricted to coastal sites.

Unfortunately, without a clear determination of the source ofthe artefacts, these results indicating maritime transportation ofraw materials continue to be preliminary. More geoarchaeologicalsurveys are needed to locate other obsidian sources in thePhilippines. The only known primary source so far, Nagcarlan inLaguna province, does not appear in archaeological assemblages ofPleistocene and Early Holocene hunter-gatherers, yet. So far, theNagcarlan obsidian has only been identified in much younger sitesand in close proximity to the outcrops.

5. Conclusion

The use of pXRF analysis of obsidian artefacts has proven to be asuitable method that can contribute to our understanding of themobility and acquisition strategies of prehistoric people, and thereconstruction of early maritime voyages. The analysis of obsidianartefacts from Ille and Bubog 1 demonstrate the capability of theTerminal Pleistocene hunter-gatherers in the region to conductlong-distance surveys and traveling by land and sea for this“valuable” raw material. Sharing the same raw material sourcepossibly also indicates a socio-cultural linkage of the prehistoricpeople in northern Palawan andMindoro, with a possible extensioninto Cebu; a maritime interaction between the geographic regionsthat was initiated before the Holocene. This evidence shows asecond, pre-Neolithic interaction sphere to the proposed mid-Holocene transportation of obsidian artefacts between Sabah,Borneo, Talaud Islands in eastern Indonesia and Mindanao in thePhilippines (Neri, 2007; Reepmeyer et al., 2011b; Tykot and Chia,1997). This discovery might also give new clues to the proposedhypothesis that the oceanic islands of the Philippines were colo-nized frommainland Southeast Asia via the Sunda Shelf and Borneoto Palawan, then Mindoro and on into Luzon (Pawlik et al., 2014).Mindoro acted hereby as an important stepping-stone in thecolonization of the Philippine archipelago.

Acknowledgments

This research is supported by an Emerging InterdisciplinaryResearch Grant of the University of the Philippines, OVPAA, Code

no. 2-002-1111212. Analysis of geochemical results were supportedby an Australian Research Council Discovery Early CareerResearcher Award to Reepmeyer (DE130100046). The fieldwork onIlin Island in 2013 and 2015 was supported by the NationalGeographic Global Exploration Fund (GEFNE 62-12 and 129-14).The Palawan Island Palaeohistory Research Project received sup-port from Rio Tuba Nickel Corporation, Coral Bay Nickel Corpora-tion, Philodrill Corp., Nido Petroleum, Leslie's Corporation,University College Dublin, and the Wilhelm G. Solheim II Founda-tion for Philippine Archaeology.

We thank Robin Torrence and the Australian Museum, Sydneyfor the use of their PXRF detector.

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