Hominin diversity in the western Indonesian archipelago during the Quaternary: a dental record perspective
Author: Noerwidi, Sofwan
Under the direction of: François Sémah et Carlos Lorenzo Merino
Muséum national d’histoire naturelle, Paris
English text
Keywords : Human paleonthology, Indonesia, Homo erectus, Homo sapiens, Meganthropus, Sundaland, Diversity, Morphometry, Fossil teeth, Man - environmental effects - Evolution, Genetic variability, Civilization - Indonesia.
Abstract
The western part of the islands of the Indonesian archipelago is one of the paleoanthropological hot spots. During Quaternary, it was impacted by climatic and sea-level changes, which could have affecting the dispersals and/or isolation of the hominins in this region. This study aims to assess the diversity of prehistoric humans in the Sundaland (Sumatra and Java) based on dental collections. We studied 715 upper and lower teeth, consisting of 290 teeth from Pleistocene hominins and 425 teeth from Holocene Homo sapiens. This study was based on the morphological and metric characterization of the teeth, including comparative morphology, classical measurements, crown size and cusp proportions, and geometric morphometrics. The four approaches of metric and non-metric comparative analysis of the western Indonesian dental record developed in this research allowed us to distinguish six dental groups : Group 1 “Meganthropus” type, Group 2 “Mojokertensis” type, Group 3 “Sangiran” type, Group 4 “Wajak” type, Group 5 “Preneolithic” type, and Group 6 “Neolithic-Paleometallic” type. Moreover, we observed that the dental pattern diversity exceeded the chronological distribution of specimens. In other words, dental diversity is not strictly following the chronology, which means that the variability is higher than previously expected. Between the Early Pleistocene (1.6 Ma) to the boundary of Middle Pleistocene (0.9 ma), there are three groups of hominins represented by the fossils from Pucangan Formation and Grenzbank layer. Group 1 Meganthropus shows the very robust size and occlusal morphological complexity which might even be related to some early African hominins. Group 2 “Mojokertensis” type and Group 3 “Sangiran” type both showed morphological complexities of the occlusal surface that would indicate their belonging to the same lineage. Based on differences with Group 1 but closeness of Groups 2 and 3, this study presumed biological continuity between hominins from the Early to Middle Pleistocene Pithecanthropus (Homo erectus), but probably a gap or a discontinuity with the Group 1 Meganthropus. Our comparative series of teeth from the Zhoukoudian site in mainland Asia was separated into these last two groups proving that there could be genetic contact between groups from Island Southeast Asia and Mainland Asia during the Middle Pleistocene. Members of the Group 4 Wajak type since the early of Mid-Pleistocene (0.78 Ma) might be identified as newcomers because of morphological differences on the Group 4 relative to the Group 2 Mojokertensis and Group 3 Sangiran type. This group, including Punung hominin (115 ka), Lida Ajer (73-63 ka), and ‘Homo wajakensis’ (37.4-28.5 ka), survived, despite the dramatic climatic change, from the Middle Pleistocene to the Late Pleistocene.The Group 5 Preneolithic type (populations of Sumatra and Java) should have evolved from the previous Group 4 Wajak type lineage. Some dental characters (simplification of the occlusal pattern, size reduction) could be the result of isolation and adaptation to an insular environment caused by the maximum of the interglacial event since 8.5 ka. The members of Group 6 Neolithic-Paleometallic, in the Late Holocene since 3.2 ka, showed conspicuous difference in dental characters leading to the hypothesis of newcomers from mainland Asia, also interbreeding with the indigenous of Group 5. Two genetic flows, from the northern and western Southeast Asia are corresponding to the Austronesian and Austroasiatic dispersals.
