Supplementary Information for Title: When did Homo sapiens first reach Southeast Asia and Sahul? Authors: James F O’Connell, Jim Allen, Martin AJ Williams, Alan N Williams, Chris SM Turney, Nigel A Spooner, Johan Kamminga, Graham Brown, Alan Cooper Corresponding author: James F O’Connell Email: [email protected] This PDF file includes: Supplementary text Figs. S1 to S4 Table S1 References for SI reference citations Supplementary Information SI.1 Hominin fossils SI.1.1 – Background notes Four species of Homo are identified on the South China-Sahul arc (1). Defining characteristics include aspects of body size, skeletal robusticity, and cranial anatomy. H. erectus (2,3). This is a widespread taxon, known from parts of Africa, Europe, North China, and Java, and dated from 1.8 Ma to the late Middle Pleistocene (<200 ka). Postcranial anatomy is relatively robust; estimated height and weight are within the modern human range. Crania are defined by a low vault, receding frontal, prominent brow ridges, moderate post-orbital constriction, and occipital angulation. Brain sizes are estimated at 700-1200 cc. Examples from Java are well represented in deposits dating 500-1000 ka. Some may have been present there as early as 1.6 Ma (4,5). Terminal dates as recent as 143 ka are cited for Javanese populations (6). Persistence to the time of anatomically modern human (AMH) arrival is possible but disputed (7,8). Skeletal and archaeological evidence indicates a presence on Flores >1.0 Ma (9,10); archaeological evidence suggests the same on Sulawesi >200 ka (11). Other interpretations, one involving Denisovans on Sulawesi, are also plausible (12). H. floresiensis (13). This is an insular dwarf known from deposits on Flores dated 60-100 ka (13,14). Brain size is estimated at c. 425 cc.; height 100-109 cm; weight 30-41 kg. Appendicular proportions differ significantly from those of H. erectus and later humans. Homo sp. teeth from c. 0.7 Ma, also on Flores, are similar in form and size to those of H. floresiensis, suggesting long- term taxonomic and locational continuity (10). Derivation is attributed to early H. erectus (10,15) or H. habilis (16,17), the former being more parsimonious. The >66 ka metatarsal from Callao, assigned to Homo sp. and widely referenced as a small-bodied H. sapiens, might represent H. floresiensis or a similarly dwarfed insular collateral (18). Archaic H. sapiens (19-21). Fossils assigned to this category are also called Late H. erectus, H. heidelbergensis, or pre-modern H. sapiens. They combine H. erectus-like features, including a 1 www .pnas.org/cgi/doi/10.1073/pnas.1808385115 massive, forwardly projecting supraorbital torus, thick cranial walls, and great basal breadth, with derived traits, including an endocranial capacity of >1200 cc, a relatively steep (non- receding) frontal, and a relatively rounded occipital. Dated East Asian specimens are Late Middle Pleistocene in age, roughly 100-400 ka. It is uncertain whether they reflect an in situ evolution of Asian H. erectus or are the product of Middle Pleistocene (>400 ka) introgression with African or European H. heidelbergensis (22). They may represent Denisovans (23). Examples are reported from China and SE Asia (e.g. Dali, Jinniushan, Maba [19]; more recently Xuchang [22]) but are so far not known from Sunda or areas further east. H. sapiens (24). Also called anatomically modern humans (AMH). Some characteristic attributes are known from Africa by 160-195 ka (25,26) and are recently reported there as early as 300 ka (27). A broader list of attributes are known from Southwest Asia at 100-130 ka (28,29) and are recently reported there as early as 177-194 ka (30). Strictly defined, AMH are identified in Africa before 50 ka, are widespread across the Eastern Hemisphere after 50 ka, and present in the Americas after 15 ka (31). They are identified by a high, rounded neurocranium, basicranial flexion, small face retracted under the frontal bone, true chin, and small, discontinuous brow ridges. Early East and Southeast Asian and Australasian examples include Tam Pà Ling (TPL 1, Laos), Niah Deep Skull (Borneo), and WLH 1, 3 (Australia). They may date earlier in South China and Southeast Asia but that is uncertain (see below). SI.1.2 - SCS arc fossils, dated 40-120 ka, said by some to represent H. sapiens SI.1.2.1 China Bailian (32). Published in Chinese, with English abstract. Two hominin teeth identified as H. sapiens; overlain by flowstone dated 160 ka via U-series. Dennell (1) is skeptical of both the identification as H. sapiens and the estimated age. Fuyan (33,34). Forty-seven teeth, dated 80-120 ka, said to be “more derived than any other anatomically modern humans, resembling middle-to-late Late Pleistocene specimens and even contemporary humans” (33). Specimens were recovered from a sandy clay (Layer 2) associated with remains of a Late Pleistocene fauna, some elements of which are extinct. U-series dates on eight speleothem fragments in the same layer range from 120-557 ka. One non-human bone from the same layer yielded a calibrated radiocarbon date of 42-43 ka. A stalagmite purportedly rooted in overlying Layer 1 yielded two U-series dates, said to indicate a minimum age of 80 ka for the underlying component and its contents. Liu et al. (33) reject the 14C date, citing technical limits of the laboratory that provided it. They favor the 120 ka U-series speleothem determination over the seven others and conclude that the human teeth in Layer 2 fall in the range 80-120 ka. Michel et al. (34) observe that the Layer 2 sediments are “suggestive of extensive fluvial activity … which raises the possibility that the deposits are reworked and actually comprise materials from different time periods.” The 42-43 ka radiocarbon date, the wide range of associated speleothem dates, and the derived quality of the teeth are consistent with this possibility. Michel et al. question whether the stalagmite from Layer 1 actually pertains to that component, rather than to underlying Layer 2. They also note that it is at least 15m away from any of the teeth, raising further questions about its relationship with the latter. They regard as inadequate 2 the appeal to faunal correlations as an additional basis for the 80-120 ka age-estimate. They conclude that the teeth may date from “the latter half of the Late Pleistocene or even more recently.” Ganquian (Tubo) (35). Published in Chinese, with English abstract. Seventeen hominin teeth identified as H. sapiens; bracketed by flowstone layers dated 94-220 ka via U-series. Dennell (1) accepts an age estimate of c. 100 ka but is skeptical of assignment of the teeth to H. sapiens. Huanglong (36,37). Sample includes seven human teeth from multiple individuals. Comparative analysis (36) shows that most of their morphological and metric features resemble those of modern H. sapiens: “Generally speaking, the Huanglong Cave human teeth look gracile and lack the archaic features usually identified on Middle and Late Pleistocene humans. [This] study also indicates that the Huanglong Cave human teeth already possess some dental features of modern East Asian populations.” The teeth were recovered from the lower portion of a red silty clay (Layer 3) in association with stone artifacts, non-human faunal remains, and dark, carbon-rich patches read as the remains of anthropogenic fires. Liu et al. (36) appeal to sediment clast size, lack of evidence of bone or artifact rounding, and the presence of the carbon patches as evidence that Layer 3 contents including human teeth are in primary context, not re-deposited from another location. Layer 3 dates originally reported from rhinoceros teeth (U-series 79.4 ± 6.3 ka, 94.7 ± 12.5 ka; ESR 34-44 ka) and a stalagmite (U-series, c. 103 ka) were seen as potentially unreliable (36,37), the former for methodological reasons, the latter because of uncertainty about sample provenience relative to the human teeth. Subsequent U-series analyses of the thin, patchily distributed flowstone capping Layer 3 yielded a date of 28 ka. Flowstones in the upper part of Layer 3 were pegged at 32-45 ka; those in the mid-lower part of Layer 3 at a composite 81.4 ± 1.1 ka. The latter estimate is seen by Liu et al. (36) as a minimum date for the human teeth. The weighted mean of three samples underlying the teeth is 101 ± 1, indicating a maximum age for the teeth; hence, the bracketing age estimate of 81-101 ka. Bae (38) is cautious about whether teeth are in primary context, citing possible fluvial or rodent disturbance. Dennell (1) expresses similar concerns. As at Fuyan, the derived quality of the teeth encourages this skepticism. Laibin (Gaitou) (39,40). The term Laibin applies to a set of hominin remains collected from Gaitou Cave in 1956. They consist of three disconnected pieces, probably once part of the same individual, including “a nearly complete hard palate with several teeth and the adjoining lower part of the body of the maxilla, a large part of the right zygomatic, and an occipital fragment” (40). They were identified by Jia and Wu (39) as H. sapiens based on a “lack of distinct archaic features.” Dennell (1) favors a date of 39-44 ka. All skeletal parts were recovered from a sandy clay layer, capped by a thick flowstone. Two U- series dates on that flowstone have a weighted mean of 38.5 ± 1.0 ka. Two dates on thinner, less extensive flowstones within the sandy clay, said to underlie sediments where the fossils were located, have a weighted mean of 44.0 ± 0.8 ka.