Iwan Kurniawan

Hominins on Flores, Indonesia, by one million years ago

Previous excavations at Mata Menge and Boa Lesa in the Soa Basin of Flores, Indonesia, recovered stone artefacts in association with fossilized remains of the large-bodied Stegodon florensis florensis. Zircon fission-track ages from these sites indicated that hominins had colonized the island by 0.88 ± 0.07 million years (Myr) ago. Here we describe the contents, context and age of Wolo Sege, a recently discovered archaeological site in the Soa Basin that has in situ stone artefacts and that lies stratigraphically below Mata Menge and immediately above the basement breccias of the basin. We show using 40Ar/39Ar dating that an ignimbrite overlying the artefact layers at Wolo Sege was erupted 1.02 ± 0.02 Myr ago, providing a new minimum age for hominins on Flores. This predates the disappearance from the Soa Basin of ‘pygmy’ Stegodon sondaari and Geochelone spp. (giant tortoise), as evident at the nearby site of Tangi Talo, which has been dated to 0.90 ± 0.07 Myr ago. It now seems that this extirpation or possible extinction event and the associated faunal turnover were the result of natural processes rather than the arrival of hominins. It also appears that the volcanic and fluvio-lacustrine deposits infilling the Soa Basin may not be old enough to register the initial arrival of hominins on the island.

Early stone technology on Flores and its implications for Homo floresiensis

In the Soa Basin of central Flores, eastern Indonesia, stratified archaeological sites, including Mata Menge, Boa Lesa and Kobatuwa (Fig. 1), contain stone artefacts associated with the fossilized remains of Stegodon florensis, Komodo dragon, rat and various other taxa. These sites have been dated to 840–700 kyr bp (thousand years before present). The authenticity of the Soa Basin artefacts and their provenance have been demonstrated by previous work, but to quell lingering doubts, here we describe the context, attributes and production modes of 507 artefacts excavated at Mata Menge. We also note specific similarities, and apparent technological continuity, between the Mata Menge stone artefacts and those excavated from Late Pleistocene levels at Liang Bua cave, 50 km to the west. The latter artefacts, dated to between 95–74 and 12 kyr ago, are associated with the remains of a dwarfed descendent of S. florensis, Komodo dragon, rat and a small-bodied hominin species, Homo floresiensis, which had a brain size of about 400 cubic centimetres. The Mata Menge evidence negates claims that stone artefacts associated with H. floresiensis are so complex that they must have been made by modern humans (Homo sapiens).

Dragon's Paradise Lost: Palaeobiogeography, Evolution and Extinction of the Largest-Ever Terrestrial Lizards (Varanidae)

Background The largest living lizard species, Varanus komodoensis Ouwens 1912, is vulnerable to extinction, being restricted to a few isolated islands in eastern Indonesia, between Java and Australia, where it is the dominant terrestrial carnivore. Understanding how large-bodied varanids responded to past environmental change underpins long-term management of V. komodoensis populations. Methodology/Principal Findings We reconstruct the palaeobiogeography of Neogene giant varanids and identify a new (unnamed) species from the island of Timor. Our data reject the long-held perception that V. komodoensis became a giant because of insular evolution or as a specialist hunter of pygmy Stegodon. Phyletic giantism, coupled with a westward dispersal from mainland Australia, provides the most parsimonious explanation for the palaeodistribution of V. komodoensis and the newly identified species of giant varanid from Timor. Pliocene giant varanid fossils from Australia are morphologically referable to V. komodoensis suggesting an ultimate origin for V. komodoensis on mainland Australia (>3.8 million years ago). Varanus komodoensis body size has remained stable over the last 900,000 years (ka) on Flores, a time marked by major faunal turnovers, extinction of the islands megafauna, the arrival of early hominids by 880 ka, co-existence with Homo floresiensis, and the arrival of modern humans by 10 ka. Within the last 2000 years their populations have contracted severely. Conclusions/Significance Giant varanids were once a ubiquitous part of Subcontinental Eurasian and Australasian faunas during the Neogene. Extinction played a pivotal role in the reduction of their ranges and diversity throughout the late Quaternary, leaving only V. komodoensis as an isolated long-term survivor. The events over the last two millennia now threaten its future survival.

Cranial morphology of Javanese Homo erectus: new evidence for continuous evolution, specialization, and terminal extinction.

Our current knowledge of the evolution of Homo during the early to middle Pleistocene is far from complete. This is not only because of the small number of fossil samples available, but also due to the scarcity of standardized datasets which are reliable in terms of landmark identification, interobserver error, and other distorting factors. This study aims to accurately describe the cranial morphological changes of H. erectus in Java using a standardized set of measurements taken by the authors from 18 adult crania from Sangiran, Trinil, Sambungmacan, and Ngandong. The identification of some obscure landmarks was aided by the use of micro-CT imaging. While recent studies tend to emphasize evolutionary conservatism in Javanese H. erectus, our results reinforce the theory that chronologically later groups experienced distinct morphological changes in a number of cranial traits. Some of these changes, particularly those related to brain size expansion, are similar to those observed for the genus Homo as a whole, whereas others are apparently unique specializations restricted to Javanese H. erectus. Such morphological specializations in Java include previously undescribed anteroposterior lengthening of the midcranial base and an anterior shift of the posterior temporal muscle, which might have influenced the morphology of the angular torus and supramastoid sulcus. Analyses of morphological variation indicate that the three crania from Sambungmacan variously fill the morphological gap between the chronologically earlier (Bapang-AG, Bapang Formation above the Grenzbank zone in Sangiran) and later (Ngandong) morphotypes of Java. At least one of the Bapang-AG crania, Sangiran 17, also exhibits a few characteristics which potentially indicate evolution toward the Ngandong condition. These strongly suggest the continuous, gradual morphological evolution of Javanese H. erectus from the Bapang-AG to Ngandong periods. The development of some unique features in later Javanese H. erectus supports the hypothesis that this Javanese lineage went extinct without making significant contributions to the ancestry of modern humans.

High-resolution record of the Matuyama–Brunhes transition constrains the age of Javanese Homo erectus in the Sangiran dome, Indonesia

A detailed paleomagnetic study conducted in the Sangiran area, Java, has provided a reliable age constraint on hominid fossil-bearing formations. A reverse-to-normal polarity transition marks a 7-m thick section across the Upper Tuff in the Bapang Formation. The transition has three short reversal episodes and is overlain by a thick normal polarity magnetozone that was fission-track dated to the Brunhes chron. This pattern closely resembles another high-resolution Matuyama–Brunhes (MB) transition record in an Osaka Bay marine core. In the Sangiran sediments, four successive transitional polarity fields lie just below the presumed main MB boundary. Their virtual geomagnetic poles cluster in the western South Pacific, partly overlapping the transitional virtual geomagnetic poles from Hawaiian and Canary Islands’ lavas, which have a mean 40Ar/39Ar age of 776 ± 2 ka. Thus, the polarity transition is unambiguously the MB boundary. A revised correlation of tuff layers in the Bapang Formation reveals that the hominid last occurrence and the tektite level in the Sangiran area are nearly coincident, just below the Upper Middle Tuff, which underlies the MB transition. The stratigraphic relationship of the tektite level to the MB transition in the Sangiran area is consistent with deep-sea core data that show that the meteorite impact preceded the MB reversal by about 12 ka. The MB boundary currently defines the uppermost horizon yielding Homo erectus fossils in the Sangiran area.

Earliest hominin occupation of Sulawesi, Indonesia

Sulawesi is the largest and oldest island within Wallacea, a vast zone of oceanic islands separating continental Asia from the Pleistocene landmass of Australia and Papua (Sahul). By one million years ago an unknown hominin lineage had colonized Flores immediately to the south, and by about 50 thousand years ago, modern humans (Homo sapiens) had crossed to Sahul. On the basis of position, oceanic currents and biogeographical context, Sulawesi probably played a pivotal part in these dispersals. Uranium-series dating of speleothem deposits associated with rock art in the limestone karst region of Maros in southwest Sulawesi has revealed that humans were living on the island at least 40 thousand years ago (ref. 5). Here we report new excavations at Talepu in the Walanae Basin northeast of Maros, where in situ stone artefacts associated with fossil remains of megafauna (Bubalus sp., Stegodon and Celebochoerus) have been recovered from stratified deposits that accumulated from before 200 thousand years ago until about 100 thousand years ago. Our findings suggest that Sulawesi, like Flores, was host to a long-established population of archaic hominins, the ancestral origins and taxonomic status of which remain elusive.

Brief communication: "Pathological" deformation in the skull of LB1, the type specimen of Homo floresiensis.

If the holotype of Homo floresiensis, LB1, suffered from a severe developmental pathology, this could undermine its status as the holotype of a new species. One of the proposed pathological indicators that still remains untested is asymmetric distortion in the skull of LB1 (Jacob et al.: Proc Natl Acad Sci USA 103 (2006) 13421-13426). Here, we present evidence that LB1 exhibits antemortem craniofacial deformities that are consistent with posterior deformational (positional) plagiocephaly. This is a relatively common condition in modern people with no serious associated health problems and does not represent a severe developmental abnormality in LB1.

New reconstruction and morphological description of a Homo erectus cranium: skull IX (Tjg-1993.05) from Sangiran, Central Java.

Skull IX (Tjg-1993.05) was unearthed from the upper stratigraphic zone (Bapang-AG levels) of the hominin-bearing sequence in Sangiran. This remarkably complete cranial specimen of Homo erectus from the early Pleistocene of Java preserves substantial portions of the vault and face. However, the distortion present in the original reconstruction has hampered detailed documentation of its morphological characteristics. We here report a new reconstruction of Skull IX that successfully recovers the original morphology and significantly differs from previous reconstructions. Detailed morphological description and the results of initial comparative analyses based on this new reconstruction are provided. The endocranial volume of Skull IX was measured as 870 cc using micro-CT data. The neurocranium of Skull IX is slightly smaller than the so far recorded smallest cranium from this zone, suggesting this individual was female. In most, but not all, aspects of the cranial vault form, details of the external surface structures, and facial morphology, Skull IX exhibits numerous similarities to the other Bapang-AG H. erectus specimens, indicating that it belonged to the Bapang-AG H. erectus population. Drawing on the expanded fossil sample of this chronoregional H. erectus group, we discuss their evolutionary status, degree of sexual dimorphism, and facial morphological variation in Afro-Asian earlier Homo specimens.

Cranial Morphology and Variation of the Earliest Indonesian Hominids

The Early Pleistocene deposits of Sangiran, Central Java, have yielded the oldest hominid fossils in Indonesia. This Sangiran assemblage is the oldest sizable hominid fossil collection so far known from Asia, and along with the African and Georgian arrays is the best comparative collection of Early Pleistocene Homo in the world. For this reason, the Sangiran hominid materials are important for understanding the dispersal and paleobiology of earlier members of our genus. However, due to ambiguous contextual documentation and the fragmentary nature of many of the existing fossils, our understanding of the taxonomic affinities and morphological variation of the earliest Indonesian hominids remains unclear. In this paper, we review recent chronostratigraphic data, and examine the Sangiran cranial remains. Contrary to previous arguments that the oldest Indonesian hominids are characterized by cranial robusticity, we propose that these hominids are actually highly variable, including both robust and gracile morphotypes. In overall cranial size and shape, and dentognathic morphology, the earliest Indonesian hominids appear to be comparable to c. 1.7 Ma early Homo erectus from East Africa. Evolutionary and taxonomic implications of these findings are discussed.

Quaternary vertebrate faunas from Sumba, Indonesia: Implications for Wallacean biogeography and evolution

Historical patterns of diversity, biogeography and faunal turnover remain poorly understood for Wallacea, the biologically and geologically complex island region between the Asian and Australian continental shelves. A distinctive Quaternary vertebrate fauna containing the small-bodied hominin Homo floresiensis, pygmy Stegodon proboscideans, varanids and giant murids has been described from Flores, but Quaternary faunas are poorly known from most other Lesser Sunda Islands. We report the discovery of extensive new fossil vertebrate collections from Pleistocene and Holocene deposits on Sumba, a large Wallacean island situated less than 50 km south of Flores. A fossil assemblage recovered from a Pleistocene deposit at Lewapaku in the interior highlands of Sumba, which may be close to 1 million years old, contains a series of skeletal elements of a very small Stegodon referable to S. sumbaensis, a tooth attributable to Varanus komodoensis, and fragmentary remains of unidentified giant murids. Holocene cave deposits at Mahaniwa dated to approximately 2000–3500 BP yielded extensive material of two new genera of endemic large-bodied murids, as well as fossils of an extinct frugivorous varanid. This new baseline for reconstructing Wallacean faunal histories reveals that Sumbas Quaternary vertebrate fauna, although phylogenetically distinctive, was comparable in diversity and composition to the Quaternary fauna of Flores, suggesting that similar assemblages may have characterized Quaternary terrestrial ecosystems on many or all of the larger Lesser Sunda Islands.