Evolutionary Anthropology 24:185–213 (2015) ARTICLE Early Hominin Biogeography in Island Southeast Asia ROY LARICK AND RUSSELL L. CIOCHON Island Southeast Asia covers Eurasia’s tropical expanse of continental shelf Solo Basin, has since produced more and active subduction zones. Cutting between island landmasses, Wallace’s than 80 Homo erectus cranial and Line separates Sunda and the Eastern Island Arc (the Arc) into distinct tectonic dental fossils. The Sangiran and Tri- and faunal provinces. West of the line, on Sunda, Java Island yields many fossils nil fossils have thick cranial vaults of Homo erectus. East of the line, on the Arc, Flores Island provides one skele- and cranial capacities of 840 to 1,059 ton and isolated remains of Homo floresiensis. Luzon Island in the Philippines cc.3 A much later set of Solo Basin has another fossil hominin. Sulawesi preserves early hominin archeology. This Homo erectus fossils, from Ngandong insular divergence sets up a unique regional context for early hominin dispersal, and related sites, have cranial isolation, and extinction. The evidence is reviewed across three Pleistocene cli- capacities reaching 1,250 cc. mate periods. Patterns are discussed in relation to the pulse of global sea-level In 2003, at Liang Bua, on Flores, shifts, as well as regional geo-tectonics, catastrophes, stegodon dispersal, and east of Wallace’s Line, Homo flore- paleogenomics. Several patterns imply evolutionary processes typical of oceanic siensis was defined on the basis of islands. Early hominins apparently responded to changing island conditions for one nearly complete skeleton and a million-and-a-half years, likely becoming extinct during the period in which fragmentary remains of several indi- Homo sapiens colonized the region. viduals.4,5 Compared to Sunda Homo erectus, the fossils from Liang Bua have a very small cranial capacity In 1859, Alfred Russell Wallace Sunda and the Arc. Wallace’s Line 3 identified two faunal provinces represents a series of sea-channel (417 cm ). In relation to most Pleis- within Island Southeast Asia (ISEA), barriers to the dispersal of large tocene early hominins, the Liang mammals between them. The provin- Bua skeleton is short (1.06 m) and ces are based primarily on the conti- has primitive wrists and large feet, 6 Roy Larick owns Bluestone Heights, an nental origin of large terrestrial as well as a late age (60 ka). Other environmental education and consulting mammals (Fig. 1, Box 1).1 West of members of the Liang Bua vertebrate firm in Cleveland, OH. He is a Paleolithic fauna share similar insular charac- archeologist who has done field work Wallace’s Line, mammalian species 6 covering Europe, Africa, and Asia. He is a have Eurasian origins; east of the ters (Box 2). When compared with founding member of the Iowa-Bandung line, “Wallacean” mammals and related species on other ISEA land- Java Project. Email: [email protected] other vertebrates show a mixture of masses, the Liang Bua fauna show Russell Ciochon is Professor of Anthro- Eurasian and Australian origins. pology and Director of Museum Studies signs of isolation on Flores for a sig- at the University of Iowa, Iowa City. He is Similar, if less provincial differentia- nificant part of the Pleistocene.7 a paleoanthropologist with field work tion can be observed for some spe- In 2007, fragmentary fossils were projects throughout Asia. He also is a cies of fish, insects, and birds. The founding member of the Iowa-Bandung collected from Callao Cave on the Java Project. Larick and Ciochon have line should pose a factor for ISEA island of Luzon, in the Philippines.8 collaborated on paleoanthropological early hominin dispersal, isolation, projects in Vietnam, China, and Indone- Because of its small dimensions and sia. Email: [email protected] and extinction. gracile morphology, a complete meta- tarsal resembles those in small- EARLY HOMININ bodied early hominins, including Homo habilis and Homo floresiensis. Key words: Sunda; insular dwarfism; island rule; BIOGEOGRAPHY IN ISLAND Homo erectus; Homo floresiensis; Marine Isotope Its date, 66.7 ka, is close to that of Stages (MIS); Java; Flores; Luzon; Sulawesi; SOUTHEAST ASIA Liang Bua. In 2014, an upper molar Timor In 1891, Eugene Dubois’ named tooth row of archaic character was Pithecanthropus erectus (now Homo recovered, as were additional small 9 VC 2015 Wiley Periodicals, Inc. erectus) based on a calotte and femur limb bones. The new Callao finds DOI: 10.1002/evan.21460 suggest a possible third group to the Published online in Wiley Online Library found at Trinil, in the Solo Basin of (wileyonlinelibrary.com). eastern Java.2 Sangiran, also in the ISEA Pleistocene hominin population 186 Larick and Ciochon ARTICLE Figure 1. Southeast Asia: sedimentary basins and catastrophe origin points of relevance to early hominin paleoanthropology. Terrestrial sur- face extends to 100 m below current sea level. We followed Huxley’s modification of Wallace’s Line208 as illustrated in Cooper and Stringer204. Boxes show areas detailed in Figure 3. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] and a second colonization east of numerous and widespread. Archeol- three sections corresponding to these Wallace’s Line. ogy therefore fleshes out early homi- events. A period framework makes Early hominins are now definitively nin biogeography. The historical for some repetition in presenting situated on Sunda and at two wide- trend of archeological research par- sites with long stratigraphic sequen- spread points on the Arc. Both Arc allels that of fossils. Recent research ces. Nevertheless, parsing regional fossil hominins have the small size provides a richer comparative base developments by period helps to and specialized skeletal traits seen in (Box 3). Stone tools are incorporated identify the effects of climate change insular evolutionary contexts and, to into the review when an excavated and several regional environmental a lesser extent, in the earliest Homo stratigraphic sequence contains catastrophes (Box 5). Figure 2 erectus from Eurasia (Dmanisi). The fauna and artifacts within a recog- presents the overall scheme. Each Arc hominins diverge greatly from all nized geological level and when a period section has a synoptic table known Sunda forms. After more than sequence-long sampling strategy has for the relevant events, sites, lithics, a century of accumulating fragmen- consistently produced Pleistocene and fauna. Table 1, for example, tary evidence, ISEA early hominin ages. presents the earlier Pleistocene biogeography is now a significant Using dated Marine Isotope Stages benchmarks. research topic. Here we review rele- (MIS) global events and a long chro- vant evidence from Sunda and the nology for regional occurrences, we OLDUVAI SUBCHRON, OR Arc within a framework of Pleisto- can begin to comprehend ISEA bio- EARLIER PLEISTOCENE cene climate change, our primary geographic events in their global goal being to evaluate potential roles contexts (Fig. 2, Box 4). Three global During the earlier Pleistocene for well-known insular evolutionary events can be tied to crucial regional (2.6-0.9 Ma), a 41-kyr orbital cycle processes in ISEA early hominin evo- biogeographic transitions: the Oldu- drove global climate. This periodic- lution (Box 2). vai paleomagnetic event, the Late ity, based on earth’s orbital obliquity, While ISEA early hominin fossils Early Pleistocene Revolution (aka exemplifies one of three such orbital are few and spatially isolated, Mid-Pleistocene Revolution), and the patterns, known as Milankovitch Pleistocene-age stone artifacts are Mid-Brunhes Event. This review has cycles.10 During this time, glacial- ARTICLE Early Hominin Biogeography in Island Southeast Asia 187 Figure 2. ISEA Pleistocene chronology and site correlation. Even-numbered MIS represent cooler phases (Northern hemispheric glacials); odd-numbered stages represent warmer phases (Northern hemispheric interglacials). MIS ages are drawn from Bowen and Sikes,272 Berger et al.,109 and Willoughby.273 Ages before MIS 19 are approximate. Since early hominin fossils are known only from sites in Java and Liang Bua, Flores, artifacts serve as the evidence of early hominins at other sites. FAD 5 first appearance datum; LAD 5 last appearance datum. Except where noted, site or event placement marks earliest occurrence. Blue lines indicate first-occurrence pre- sumed hominin continuous occupation in each regional site sequence unless otherwise noted. Sites with named formations and/or geologic designations: Lower Lahar, Lower Lahar Unit (Sangiran Formation); Sangiran, Sangiran Formation; Bapang, Bapang Forma- tion; Ngebung, Bapang Formation; Song Terus, karst cave; Ngandong, 20 m terrace of Solo River; Wolo Sege, Tangi Talo, Mata Menge, Boa Lesa, and Kobatuwa, Ola Kile Formation; Liang Bua, karst cave; S Enrile Q, Awidon Mesa Formation; Cagayan, Ilagan and Awidon Mesa Formations; Arubo, Sierra Madre foothills; Callao, karst cave; Cabenge, Walanae Basin fill. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] interglacial cycles were relatively the size and distribution of Sunda mammals arrived on an emergent short and had low temperature landmasses. Northern Hemisphere Sunda.19–21 amplitude.11,12 Toward the middle of glacial ice advanced significantly this phase, the Olduvai Subchron between about 1.8 and 1.74 Ma (MIS marks a brief geomagnetic pole 62, 60, and 58), about 1.56 Ma (MIS Sunda reversal event, 1.98-1.79 Ma.13 Soon 52), between 1.24 and 1.1 Ma (MIS Sangiran, Java (Indonesia) after Olduvai, increases in monsoon 36, 34, and 30), and about 0.9 Ma intensity were recorded in the terres- (MIS 22).16 During these stages, sea- Much of the Solo Basin lies at trial contexts of the Lake Turkana level lowstands opened emergent about 78 S latitude and sits above the (Kenya) and Heqin (China) landmasses throughout ISEA.17,18 It Indonesian subduction zone (Fig. basins.14,15 Glacial-interglacial was, apparently, just after the Oldu- 3A).