Supporting Information

Masaki Fujita et al.

SI Text 1. Stratigraphy, dates, and periods of human occupation at Sakitari Cave The excavated sequence at Trench I and Pit 1 show inclination of about 20° toward the cave’s interior with no signs of substantial water flow or talus cone (Fig. S2), indicating dominantly gradual, colluvial sedimentary process from the outside of the cave. Immediately below the top soil, ~30-cm thick, multi-stratified flowstone (FS) containing shards of Jomon potteries spread all over the Trench I. This FS layer is dated to between 2,800 and 11,000 cal BP, suggesting multiple episodes of flowstone formation and erosion during the early−middle Holocene period. The clayey Pleistocene strata were protected beneath this FS layer. We recognized three major units within the terminal Pleistocene sequence, Layer I, II, and III from top down. All these units include charcoal fragments, but Layer II is distinguished from Layer I and III primarily by significantly higher density of charcoals and the resultant dark color. Layer II is also less compact compared to Layer I and the uppermost part of Layer III. Layer II was further subdivided into two charcoal belts (II-1B and II-2), and the sediments above (II-1A) and below (II-1C) the upper charcoal belt (II-1B)(Fig. 2, Fig. S2). Layer III was also subdivided into the upper and the lower parts by the boundary drawn about 2 m below the ground surface, primarily because the remains of two of extinct deer were found only from the latter levels. AMS radiocarbon dating shows that Layer I is 13,000−16,500 cal BP, Layer II is 20,000−23,000 cal BP, and Layer III is 23,500−25,000 cal BP (the upper part) and 26,000−36,500 cal BP (the lower part) (Fig. 3, Table S1). The dates for the 39 samples are consistent with the stratigraphy, indicating little post-depositional disturbance of the terminal Pleistocene strata. A single marine shell sample (PLD-19424) from Layer I returned an unexpectedly old age (27,300 cal BP) for that layer. This may be an instance of

1 an upworked older shell, or otherwise people collected an old shell for some use. A charcoal (PLD-24993) and a (PLD-27744) which show relatively young ages obtained from for the layer III probably were intruded from layer II. Identified wood charcoal samples include genus Camellia and possibly Symplocaceae. The dates obtained for these samples may be older than the depositional dates by as much as their life durations of several hundreds to a thousand years. Other samples may have been variously affected by old carbon from the karst. Still, the remarkable stratigraphic consistency of the obtained dates suggest that such effects are minimal, if any. The terminal Pleistocene layers (as well as the Holocene FS layer) offer various evidence of human activities such as charred remains, dense charcoals, humanly transported marine shells, shell and stone artifacts, as well as human remains (Fig. 4). Although there appear to be small chronological gaps between the dated samples from Layer I and II (3,500 years) and Layer II and III (2,000 years), the evidence of similar largely seasonal use of this cave throughout the sequence suggests continuous occupation of Palaeolithic people on the Okinawa Island throughout the terminal Pleistocene. The timing when people began to use this cave is a question we cannot answer at the present stage of the research. An atlas and rib of a human infant individual were found at Pit 1, from the lower part of Layer III. AMS ages for three charcoal and freshwater snail samples collected from the vicinity of the human remains are 28,700−31,400 cal BP (1σ ranges for the three samples combined), and humans were clearly at this cave by this time. About 10 cm below the human level, eleven isolated cervid bones including a charred lumber vertebra, as well as freshwater crabs and snails, some of which are also charred, were found together with a charcoal fragment dated to 36,500 cal BP (PLD-16469 in table S1).

2. Stone artifacts The terminal Pleistocene strata of Sakitari Cave have so far yielded only a few stone artifacts: three quartz flakes from Layer I and a possible grindstone made of sandstone from Layer II. Both stones are not available locally and must have been transported into the cave

2 by humans. The quartz flakes are tiny (<3 cm in length) and amorphous (Fig. 4). They bear patterns of breaks most similar to experimentally knapped quartz (1, 2), but their small sizes and amorphous shapes make it difficult to infer their function. Grindstones and/or retoucher must have been necessary to manufacture the fishhooks and scrapers (Fig. 5, Fig. S8). A small sandstone which have smoothed surface probably was used for these purposes. High-quality lithic raw materials such as siliceous stones are unavailable in the karstic areas of southern Okinawa Island where the Sakitari Cave is located. The nearest outcrop of quartz is 30 km away from the cave and that of chert is 50 km away. We hypothesize that this explains the general paucity and crudeness of stone tools from Okinawa; Palaeolithic people here probably relied on other types of raw materials such as marine shells described below and in the main text.

3. Bivalve shell tools Morphotypes The terminal Pleistocene marine bivalve assemblage from Sakitari Cave is mainly represented by Veneridae and Septifer bilocularis (Table S2). The Veneridae includes larger species (Callista chinensis and Meretrix sp. cf. lusoria) that were used as tools, and smaller species (Sunetta kirai) perforated to create beads. A comparatively small bivalve species, S. bilocularis, was also used as tools. These bivalve tools are described below. Table S3 lists the larger Veneridae bivalves so far recovered from the terminal Pleistocene strata of Sakitari Cave. All of these 22 specimens are fragmented. Many of them bear small flaking scars indicative of retouch and/or use-wear, and thus are identified as tools, while others may include debris from the tool manufacturing (Figs. S3 and S5−S7). We classified these Veneridae fragments into the following three morphotypes: 1) fragments with hinge, 2) trapezoid form, and 3) other amorphous fragments. The longer margin of a trapezoid form piece consists of (largely) intact, convex ventral margin of the shell (the margin opposite to the umbo). The shorter margin is a broken, often concave, retouched edge on its dorsal side (near the umbo). Several tiny shell chips were also found from Layer II, suggesting that the shell tools were manufactured at this cave.

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The trapezoid form dominates the Sakitari Cave fragmented Veneridae shell assemblage: seven specimens were found from Layer II and another from the uppermost part of Layer III (Figs. 4 and 5). According to an experimental study (3), their manufacturing process is as follows: First, a shell is fragmented by dealing a blow to the center of its external surface. Next, a trapezoidal piece is selected from the broken fragments. Then, its fractured, shorter margin (on the dorsal side) is retouched from the external surface of the shell to create a concave margin. In contrast to the fragmented conditions of these larger and thicker Veneridae, the smaller S. bilocularis bivalves are more or less complete (Fig. 5D). Two of the three S. bilocularis specimens bear possible traces of use on their ventral margins as explained below (Fig. S7).

Use-wear analysis The use-wear features on the modern experimental Veneridae shells (Fig. S4) were compared to the fragmented bivalves from Sakitari Cave (Table S3 and Figs. S5−S7). Out of the eight trapezoidal Veneridae fragments, the following three specimens from Layer II bear use-wear traces on their short, concave margins (Fig. S5). No. 4 shows a polished micro-plane and striations running perpendicularly to the edge. The concave morphology of the working edge and the above use-wear pattern suggest that this piece was used to scrape bar-like objects. The polish exhibits bright, smooth, flat appearance similar to the polish observed on the experimental specimens used for bamboo-scraping (fig. S4A). The polish resulted from wood-scraping also exhibited comparable features with that from bamboo-scraping. Hide-scraping produced a matte, rounded polish surface on the edge (Fig. S4B), a pattern identical to the use-wear on lithic specimens (4). In contrast, scraping an antler or a bone did not develop polish but yielded an abraded surface (Fig. S4C). Accordingly, No. 4 was probably used for scraping bamboo or wood. No. 5 and No. 6 (Fig. S5) also show polish and striations or rounding on their concave edges, suggesting utilization as scrapers, although the polish on these latter pieces is not developed enough to infer the worked materials.

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Among the other non-trapezoid Veneridae fragments, three pieces showed clear use-wear traces. One of them (No. 1 in Fig. S3) shows polish, abrasion, and striations running perpendicular to the retouched edge, suggesting its function as a scraper. The other two artifacts (Nos. 2 and 15 in Fig. S6) exhibit alternate edge-damages, a pattern frequently observed on experimental cutting-tools made of shells (this study) as well as stones (5, 6, 7). In addition, No. 2 shows abrasion, polish, and striations running parallel to the edge on both the external and internal sides of the dorsal margin, supporting cutting activity with this edge. The same formation pattern of polish and striations are also observed on No. 15. The worked materials for the above three specimens could not be assessed because of minimal polish on these shells and the small sample sizes of our experiments. Among the three S. bilocularis specimens, one exhibits macroscopic, long striations on the interior surface of the ventral margin and flake scars on the external side (Fig. S7A, B). Another one shows abrasion on the internal side of the ventral margin that had removed microtopographic shell (Fig. S7C). Because no obvious micro-wear traces were observed on the three pieces, post-depositional process cannot be completely excluded as a causative factor of the above macroscopic features. However, the fact that these edge damages are limited to the ventral margin of these S. bilocularis shells supports their utilization as tools.

Discussion The shell-tools from the Pleistocene levels of Sakitari Cave show some diversity as well as standardization in their manufacturing process, shape, and utilization. Larger marine bivalves were often modified to trapezoidal forms with their shorter margins set on the dorsal sides and often retouched to produce concavity suitable for scraping bamboos, woods, or other bar-like objects. Some bivalve tools are amorphous but they include not only scrapers but also cutting tools. Smaller bivalves were also used as tools but without any prior modifications. These aspects contrast remarkably to the simple and poor lithic industry described above.

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4. Faunal analyses Faunal elements Faunal compositions were similar across the terminal Pleistocene layers, although there is variation in their densities (Fig. S8, Table S4). Freshwater crabs and freshwater snails are dominant in all these layers but are particularly abundant in Layer II. Small-sized vertebrates consists of mammals (Rodentia and Insectivora), birds including Okinawa rail (Gallirallus okinawae), snakes such as a pit viper species Okinawa Habu (Protobothrops flavoviridis), lizards (Agamidae and Eublepharidae?), frogs, freshwater fish represented by Giant mottled eel (Anguilla marmorata), and marine fish. Because marine fish and freshwater such as eels, freshwater crabs, and freshwater snails cannot live inside the dry cave, they must have been food residues brought by humans. This is supported by the observation that 3 to 12 % of the freshwater crabs and freshwater snails are charred (Fig. S8) as their dark colors tell. As shown in fig. S9, our XRD analysis of freshwater snails indicates that the charred black-colored sample show an calcite XRD pattern, whereas the white-colored sample preserves the original aragonite mineralogy of freshwater snails. Heating at ~500ºC or higher in fire can explain such mineralogical transformation (8). Many of the vertebrate remains are also charred (Table S4, Fig. S8C), suggesting that they were eaten by humans. Interestingly, however, none of the land snail remains are charred (Fig. S8B). They are commonly distributed around the cave and were probably introduced to the sediments through natural depositional processes. Another remarkable characteristic of the Sakitari Cave faunal assemblage is paucity of the large/medium-sized mammals (Fig. S8, Table S4). Wild boars from layers I and II and extinct cervids from the lower level of layer III were fragmented and small in number (Table S4).

Size bias in crabs Despite several freshwater crab species living around the present-day Sakitari Cave, the excavated species was almost exclusively Japanese mitten crab, E. japonica. This is the largest freshwater crab species in Okinawa and has been used as food by local people.

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Combined with the above evidence of burning, such a biased species composition strongly suggests that they were captured by humans to eat. Moreover, fig. S10 shows that the E. japonica remains are clearly biased toward larger individuals with the carapace widths being >55 mm and the mode value around 80 cm. This latter value corresponds to the largest individuals in the extant population. The observed bias in size is another evidence for artificial selection and accumulation of these crab remains at Sakitari Cave. Such large individuals of E. japonica are easily caught at autumn nights when they migrate downstream for reproduction in coastal areas (9−11). Autumn is the best season to eat this crab species because they store much nutrient by developping their hepatopancreases before reproduction. The unusual bias in size is best explained by the hypothesis that Palaeolithic people visited Sakitari Cave in autumn to target such large and delicious crabs.

Isotopic analysis Seasonality of human activity at Sakitari Cave is also supported by the oxygen isotopic analysis of the aragonite shells of freshwater snails, libertina, which records the temperature changes in the ambient water environment during growth. δ18O values measured at about 25 successive spots in each snail specimen typically show a sine-curve pattern as seen in the example of fig. S11. The maximum and minimum levels in this curve can be regarded as mid-winter and mid-summer positions, respectively. This δ18O curve was fit to the curve of the modern air temperature (average during the last 20 years) at Naha City located ~12 km NW of Sakitari Cave, and the season corresponding to the last δ18O value measured at the outer of the shell was estimated for each snail specimen (Table S5). The results suggest that these shells were consumed by humans mostly in autumn (64%) and secondly in summer (32%).

Discussion ‒ selectivity and seasonality The faunal assemblage from Sakitari Cave suggests that Palaeolithic people did not frequently consume large/medium-sized animals here. This is not due to the absence of

7 such animals, because a large collection of wild boar and deer remains from Minatogawa Fissure (12) located only 1 km away from Sakitari Cave clearly indicate that these animals were abundant during the LGM in this area. The above analyses strongly suggest that Sakitari Cave had been a seasonal camp to capture and eat aquatic animals represented by freshwater crabs and freshwater snails. The hunter-gatherers repeatedly visited the cave in autumn, the best season to have the freshwater crab (E. japonica) in terms of meat quantity, nutrition, and taste. Another notable finding is the occurrence of eels and marine fish from the Pleistocene layers. If these difficult-to-catch aquatic animals were fished using fishhooks recovered from Layer II, it is intriguing if the fishhook technology existed even earlier in Okinawa, at the time of the lower part of Layer III that also yielded eel and fish remains (Table S4).

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Table S1. AMS 14C dates obtained from Trench I and Pit 1 of Sakitari Cave. layer specimen lab. code δ13C 14C BP cal BP (1σ range) ref. C (ND) MTC-16902 -26.2 2,695±35 2,820-2,843 MS (T. granosa ) MTC-16901 -5.0 8,600±50 9,192-9,361 FS MS (T. granosa ) PLD-23299 -1.39 8,720±35 9,362-9,454 MS (T. granosa ) MTC-16903 -4.3 8,970±50 9,536-9,676 MS (G. erosa ) MTC-16904 -7.9 10,230±50 11,157-11,266 C (genus Camellia ) PLD-19423 -26.26±0.12 12,445±40 14,374-14,741 12 C (genus Symplocaceae ?) PLD-19425 -26.02±0.12 12,475±40 14,466-14,875 12 C (ND) MTC-16133 -27.4 12,200±60 14,005-14,180 upper half LS (S. mercatoria ) MTC-16134 -8.4 12,240±60 14,041-14,228 I FC (E. japonica ) MTC-16135 -5.4 11,510±70 13,291-13,427 MS (Veneridae) PLD-19424 1.82±0.11 23,370±70 27,219-27,412 12 FC (E. japonica ) MTC-16136 -4.3 12,590±60 14,815-15,100 lower half C (ND) MTC-16137 -27.8 13,680±70 16,335-16,625 LS (S. mercatoria ) MTC-16138 -7.4 13,370±60 15,985-16,196 C (broadleaf tree) PLD-19991 -23.26±0.32 16,910±60 20,299-20,507 12 II-1B C (genus Camellia ) PLD-19992 -27.66±0.27 16,370±60 19,635-19,864 12 C (ND) PLD-23422 -27.58±0.19 17,870±50 21,561-21,778 II-1C C (ND) PLD-23423 -28.26±0.17 17,565±50 21,104-21,345 uppermost C (ND) PLD-23288 -28.55±0.24 18,820±60 22,546-22,772 II-2 C (ND) PLD-23289 -25.06±0.34 18,590±70 22,382-22,552 II FC (E. japonica ) MTC-17125 -8.6 15,570±90 18,737-18,909 lower II-2 C (ND) PLD-21783 -26.73±0.21 18,950±60 22,695-22,935 13 LS (S. eucosmia ) MTC-17128 -5.7 19,040±90 22,781-23,068 FS (S. libertina ) MTC-17126 -11.4 19,160±100 22,908-23,251 C (ND) MTC-17127 -28.4 19,190±100 22,960-23,291 C (ND) PLD-15690 -24.17±0.15 19,260±70 23,055-23,344 12 (Pit 1) C (ND) PLD-16225 -27.62±0.17 19,340±50 23,155-23,425 12 C (ND) PLD-24993 -85.99±0.56 17,290±700 20,087-21,807 upper III C (ND) PLD-24994 -30.45±0.19 19,550±50 23,450-23,665 C (ND) PLD-23424 -24.87±0.20 21,010±60 25,260-25,480 FS (S. libertina ) PLD-24990 -11.27±78 24,170±80 26,104-26,397 FS (S. libertina ) PLD-24991 -10.94±0.21 24,640±80 26,624-26,844 C (ND) PLD-16224 -26.41±0.21 24,410±70 28,356-28,603 12 vicinity of C (broadleaf tree) PLD-30878 -25.90±0.25 24,910±70 28,791-29,039 the human C (broadleaf tree) PLD-30879 -27.56±0.25 26,460±80 30,663-30,874 remain C (broadleaf tree) PLD-30880 -30.62±0.24 27,600±90 31,261-31,452 lower III FS (S. libertina ) PLD-27744 -17.57±0.13 19,990±80 23,928-24,172 (Pit I) LS (A. scepasma ) PLD-27745 -10.73±0.17 27,730±150 31,301-31,585 C (broadleaf tree) PLD-27743 -27.73±0.18 30,690±210 34,421-34,839 vicinity of LS (A. scepesma ) PLD-27741 -8.52±0.21 29,480±180 33,535-33,860 the deer LS (A. scepesma ) PLD-27742 -6.11±0.15 30,850±210 34,566-34,792 remains C (ND) PLD-16469 -24.09±0.16 32,650±130 36,335-36,701 12 C, wood charcoal; MS, marine shell; FS, freshwater snail; LS, land snail; FC, freshwater crab. Taxon of each specimen was described in the bracket; ND, Taxon not determined.

Table S2. Marine shells from the Pleistocene layers of Sakitari Cave. Layer Layer Layer Layer Layer total I II-11) II-2 II 2) III Bivalvia Veneridae including Callista chinensis, 1 6 13 1 2 23 Meretrix sp. cf. lusoria, and Sunetta kirai . Septifer bilocularis 0 0 3 0 0 3 Asaphis violascens 1 0 0 0 0 1 indeterminable species 0 2 3 0 0 5 Scaphopoda Dentalium sp. cf. octangulatum 0 0 1 0 0 1 Pictodentalium formosum 0 0 1 0 0 1 Conus sp. cf. flavidus 0 0 0 1 0 1 Haliotis diversicolor (Osumi type) 1 0 3 0 0 4 "Trochus" spp. 1 0 2 0 0 3 Lunella moniliformis 2 0 0 0 0 2 Monodonta labio 1 0 0 0 0 1 Pyrene testudinaria 1 0 0 0 0 1 indeterminable species 0 0 1 0 0 1 indeterminable species 0 0 2 0 0 2 Total 8 8 29 2 2 49 ％ 16.3 16.3 59.2 4.1 4.1 100.0 1) Materials from layers II-1A, -1B, and -1C. 2) Materials from unknown sublayers within Layer II. Table S3. Basic information and use-wear observed in larger Veneridae bivalves from the Pleistocene levels of Trench I at Sakitari Cave. length width thickness weight No. Layer morphotype use-wear traces function remarks (mm) (mm) (mm) (g) 1 III upp. 17.9 27.7 7.3 2.8 hinge polish, abrasion scraping polish, abrasion, 2 II-2 14.2 26.0 6.3 1.5 hinge cutting fig. S7 striations, edge-damage 3 II-2 27.3 38.3 3.3 3.3 trapezoid no use-wear traces bamboo or wood 4 II-2 19.8 28.9 2.5 1.9 trapezoid polish, abrasion, striations fig. S6 scraping scraping 5 II 20.2 28.6 3.0 1.9 trapezoid polish, striations fig. S6 (+cutting?) 6 II-2 24.8 27.6 2.0 1.9 trapezoid polish, rounding scraping fig. S6 7 II-2 22.5 46.4 3.0 2.6 trapezoid (matrix not yet cleaned) 8 II-2 20.5 21.2 2.3 1.5 trapezoid (matrix not yet cleaned) 9 II-2 26.2 30.6 4.0 3.5 trapezoid (matrix not yet cleaned) 10 III upp. 25.2 22.6 1.7 1.1 trapezoid (matrix not yet cleaned) 11 II-1 27.7 27.9 2.2 1.8 amorphous no use-wear traces 12 II-1 24.4 21.0 2.5 1.1 amorphous no use-wear traces 13 II-2 47.2 14.2 2.3 2.7 amorphous weak polish 14 II-1 34.3 17.5 2.2 1.3 amorphous no use-wear traces polish, striations, edge- 15 II-2 18.0 21.2 2.3 1.1 amorphous cutting fig. S7 damage 16 II-2 16.2 17.9 2.3 0.8 amorphous no use-wear traces 17 II-1 18.4 14.7 6.0 0.8 amorphous no use-wear traces 18 II-2 16.6 11.1 1.5 0.5 amorphous abrasion, soil sheen PDSM 19 II-1C 18.0 10.6 4.0 0.6 amorphous no use-wear traces 20 II-2 upp. 19.1 13.7 2.1 0.7 amorphous abrasion, soil sheen PDSM 21 II-2 22.8 14.4 2.0 0.8 amorphous no use-wear traces 22 II-1 22.7 25.1 7.1 2.7 hinge (matrix not yet cleaned) PDSM: post-depositional surface modification Table S4. Number of identified vertebrate bones from Sakitari Cave. Layer III Layer III taxon Layer I Layer II (upper) (lower) total 9 4 0 0 wild boar burnt 0 0 0 0 total 0 0 0 11 extinct cervids burnt (%) 0 0 0 1 (9%) medium total 37 10 1 2 mammals (nd) burnt (%) 8 (22%) 4 (40%) 1 (100%) 1 (50%) total 55 97 106 251 small mammals burnt (%) 5 (9%) 6 (6%) 6 (6%) 17 (7%) total 2 14 25 36 birds burnt (%) 0 5 (36%) 3 (12%) 5 (14%) total 44 79 184 318 reptiles burnt (%) 9 (21%) 1 (1%) 10 (5%) 19 (6%) total 14 92 70 152 frogs burnt (%) 4 (29%) 8 (9%) 14 (20%) 18 (12%) freshwater fish total 0 6 10 20 (eel) burnt (%) 0 0 0 1 (5%) total 1 8 0 0 marine fish burnt (%) 1 (100%) 3 (38%) 0 0 total 1 14 3 6 fish (nd) burnt (%) 0 1 (7%) 0 1 (17%) nd: detailed taxon indeterminable Table S5. Results of the oxigen-isotope analysis of the freshwater snail (S. libertina ) shells from Sakitari Cave. the lowest δ18O the highest δ18O δ18O at the sample code layer season (summer) (winter) outer lip SAK11-FWS-526 I -5.58 -2.72 -4.51 autumn SAK11-FWS-527 I -5.04 -3.05 -4.28 autumn SAK11-FWS-528 I -5.63 -2.45 -4.09 autumn SAK11-FWS-530 I -4.87 -2.97 -4.82 summer? SAK11-FWS-531 I -5.15 -3.64 -4.34 autumn SAK11-FWS-532 I -5.14 -2.57 -4.96 summer SAK11-FWS-533 I -5.32 -2.39 -4.13 autumn SAK11-FWS-534 I -5.75 -3.07 -4.85 nd SAK11-FWS-535 I -5.55 -3.12 -4.59 autumn? SAK11-FWS-708 I -6.31 -3.11 -4.06 autumn SAK11-FWS-709 I -5.61 -3.30 -4.02 autumn SAK11-FWS-720 I -5.20 -2.11 -2.56 winter SAK11-FWS-721 I -5.60 -3.28 -4.62 nd SAK11-FWS-722 I -5.66 -2.91 -5.25 autumn SAK11-FWS-725 I -6.22 -2.18 -5.92 nd Average I -5.12 -2.92 -4.21 SAK12-FWS-A II-2 -5.51 -2.68 -4.65 early summer SAK12-FWS-B II-2 -5.38 -2.91 -5.38 summer SAK12-FWS-C II-2 -4.93 -2.23 -4.28 autumn SAK12-FWS-D II-2 -4.94 -3.60 -3.85 nd SAK12-FWS-E II-2 -4.94 -2.20 -3.55 autumn SAK12-FWS-F II-2 -5.00 -2.09 -4.65 nd SAK12-FWS-G II-2 -4.63 -2.61 -3.86 autumn SAK12-FWS-H II-2 -5.52 -3.10 -4.54 nd SAK12-FWS-I II-2 -5.52 -2.99 -3.72 autumn SAK12-FWS-J II-2 -5.45 -3.13 -4.38 autumn SAK12-FWS-K II-2 -4.87 -2.30 -4.10 autumn SAK12-FWS-L II-2 -4.00 -2.02 -3.60 early summer SAK12-FWS-M II-2 -4.95 -2.71 -4.60 summer SAK12-FWS-N II-2 -4.93 -3.32 -3.92 autumn SAK12-FWS-O II-2 -4.86 -2.69 -4.12 autumn SAK12-FWS-P II-2 -4.72 -1.64 -4.72 summer SAK12-FWS-Q II-2 -5.09 -2.64 -3.59 nd SAK12-FWS-R II-2 -4.78 -3.02 -4.01 autumn SAK12-FWS-S II-2 -5.30 -3.14 -4.51 early summer SAK12-FWS-T II-2 -5.39 -3.08 -4.72 autumn Average II-2 -5.04 -2.71 -4.24 nd: season indeterminable due to unclear seasponal variation in the δ18 O pattern

Figure legends Fig. S1. Plan (left) and longitudinal section (right) of Sakitari Cave. The present report focuses on Trench I and Pit 1.

Fig. S2. Trench I and its section. (A) Trench I and the west entrance viewed from inside the cave. (B) Section of the southern wall of Trench I. Layer II is relatively dark and contains two charcoal-rich sublayers (II-1B and II-2).

Fig. S3. Fragmented larger Veneridae shell assemblage from Layers II and III. Nos. 1‒2, fragments containing the hinges; Nos. 3‒10, trapezoidal forms; Nos. 11‒22, amorphous fragments. The arrow heads indicate small flaking scars. Note that the shorter (upper) margin of No. 3 is broken.

Fig. S4. Use-wear formed on the experimental Veneridae shell specimens. (A) Bamboo-whittling for 20 minutes yielded polish and striations; (B) Dry hide-scraping for 20 minutes yielded polish, rounding, and striations; (C) Bone-scraping for 50 minutes yielded abrasion; (D) Bamboo-sawing for 20 minutes yielded polish and striations; (E) Hide-cutting for 20 minutes yielded polish and striations; (F) Bone-sawing for 20 minutes yielded polish, rounding and striations.

Fig. S5. Trapezoidal Veneridae tools showing use-wear traces indicative of scraping. Left panels: from left to right, external view, mid-line cross section, and internal view of each shell fragment. Right panels: magnified photographs of the parts indicated in the left panel. (A) No. 4 shows a polished micro-plane and striations running perpendicular to the concave edge; (B) No. 5 shows polish and striations; (C) No. 6 shows polish and rounding. Note that these use-wear traces are restricted to the external side of the concave edges.

Fig. S6. Non-trapezoid Veneridae artifacts showing use-wear traces indicative of cutting. (A) External side of the dorsal margin of No. 2 shows polish associated with striations; (B) Internal side of the same edge shows edge-damage and abrasion; (C) External side of the retouched edge of No. 15 shows edge-damage; (D) Internal side of the same edge shows polish.

Fig. S7. Specimens of Septifer bilocularis showing possible use-wear traces. (A) External side of the same edge shows edge-damage; (B) Interior surface of the ventral margin shows macroscopic striations and abrasion; (C) Internal surface of the ventral margin shows abrasion.

Fig. S8. Faunal composition in each Pleistocene layer at Sakitari Cave. (A) Minimum number of individuals (MNI) of freshwater crabs and snails; (b) MNI of land snail taxa; (C) Number of identified specimens (NISP) of small-sized vertebrates. Grey area indicate charred remains. Note that the vertical azes are not identical between different panels.

Fig. S9. The results of the XRD analyses of unburnt (white) and burnt (black) snail specimens from Layer II-2. The white specimen shows aragonite pattern whereas the black one calcite pattern.

Fig. S10. Size (carapace width) distribution of Eriocheir japonica estimated from the length of movable pincer. Large individuals with carapace width >55 mm are dominant in all Pleistocene layers. Individuals with the carapace width of ~80 mm is the largest class in the living population, but those larger than this size are not uncommon from the Pleistocene levels of Sakitari Cave.

Fig. S11. An example of isotopic analysis of freshwater snail. The lower left panel shows the sampling spots on a shell specimen (SAK11-FWS-722). The δ18O curve derived from each of the shell specimens (left line graph) is compared with the annual temperature pattern at Naha City (right line graph) to infer the season at the outer lip of the shell.

References cited

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