Maxime Aubert

New evidence for a 67,000-year-old human presence at Callao Cave, Luzon, Philippines

Documentation of early human migrations through Island Southeast Asia and Wallacea en route to Australia has always been problematic due to a lack of well-dated human skeletal remains. The best known modern humans are from Niah Cave in Borneo (40-42ka), and from Tabon Cave on the island of Palawan, southwest Philippines (47+/-11ka). The discovery of Homo floresiensis on the island of Flores in eastern Indonesia has also highlighted the possibilities of identifying new hominin species on islands in the region. Here, we report the discovery of a human third metatarsal from Callao Cave in northern Luzon. Direct dating of the specimen using U-series ablation has provided a minimum age estimate of 66.7+/-1ka, making it the oldest known human fossil in the Philippines. Its morphological features, as well as size and shape characteristics, indicate that the Callao metatarsal definitely belongs to the genus Homo. Morphometric analysis of the Callao metatarsal indicates that it has a gracile structure, close to that observed in other small-bodied Homo sapiens. Interestingly, the Callao metatarsal also falls within the morphological and size ranges of Homo habilis and H. floresiensis. Identifying whether the metatarsal represents the earliest record of H. sapiens so far recorded anywhere east of Wallaces Line requires further archaeological research, but its presence on the isolated island of Luzon over 65,000 years ago further demonstrates the abilities of humans to make open ocean crossings in the Late Pleistocene.

The Later Stone Age calvaria from Iwo Eleru, Nigeria: morphology and chronology

Background In recent years the Later Stone Age has been redated to a much deeper time depth than previously thought. At the same time, human remains from this time period are scarce in Africa, and even rarer in West Africa. The Iwo Eleru burial is one of the few human skeletal remains associated with Later Stone Age artifacts in that region with a proposed Pleistocene date. We undertook a morphometric reanalysis of this cranium in order to better assess its affinities. We also conducted Uranium-series dating to re-evaluate its chronology. Methodology/Principal Findings A 3-D geometric morphometric analysis of cranial landmarks and semilandmarks was conducted using a large comparative fossil and modern human sample. The measurements were collected in the form of three dimensional coordinates and processed using Generalized Procrustes Analysis. Principal components, canonical variates, Mahalanobis D2 and Procrustes distance analyses were performed. The results were further visualized by comparing specimen and mean configurations. Results point to a morphological similarity with late archaic African specimens dating to the Late Pleistocene. A long bone cortical fragment was made available for U-series analysis in order to re-date the specimen. The results (∼11.7–16.3 ka) support a terminal Pleistocene chronology for the Iwo Eleru burial as was also suggested by the original radiocarbon dating results and by stratigraphic evidence. Conclusions/Significance Our findings are in accordance with suggestions of deep population substructure in Africa and a complex evolutionary process for the origin of modern humans. They further highlight the dearth of hominin finds from West Africa, and underscore our real lack of knowledge of human evolution in that region.

Revised stratigraphy and chronology for Homo floresiensis at Liang Bua in Indonesia

Homo floresiensis, a primitive hominin species discovered in Late Pleistocene sediments at Liang Bua (Flores, Indonesia), has generated wide interest and scientific debate. A major reason this taxon is controversial is because the H. floresiensis-bearing deposits, which include associated stone artefacts and remains of other extinct endemic fauna, were dated to between about 95 and 12 thousand calendar years (kyr) ago. These ages suggested that H. floresiensis survived until long after modern humans reached Australia by ~50 kyr ago. Here we report new stratigraphic and chronological evidence from Liang Bua that does not support the ages inferred previously for the H. floresiensis holotype (LB1), ~18 thousand calibrated radiocarbon years before present (kyr cal. bp), or the time of last appearance of this species (about 17 or 13–11 kyr cal. bp). Instead, the skeletal remains of H. floresiensis and the deposits containing them are dated to between about 100 and 60 kyr ago, whereas stone artefacts attributable to this species range from about 190 to 50 kyr in age. Whether H. floresiensis survived after 50 kyr ago—potentially encountering modern humans on Flores or other hominins dispersing through southeast Asia, such as Denisovans—is an open question.

U-series and radiocarbon analyses of human and faunal remains from Wajak, Indonesia

Laser ablation U-series dating results on human and faunal bone fragments from Wajak, Indonesia, indicate a minimum age of between 37.4 and 28.5 ka (thousands of years ago) for the whole assemblage. These are significantly older than previously published radiocarbon estimates on bone carbonate, which suggested a Holocene age for a human bone fragment and a late Pleistocene age for a faunal bone. The analysis of the organic components in the faunal material show severe degradation and a positive δ(13)C ratio indicate a high degree of secondary carbonatisation. This may explain why the thermal release method used for the original age assessments yielded such young ages. While the older U-series ages are not in contradiction with the morphology of the Wajak human fossils or Javanese biostratigraphy, they will require a reassessment of the evolutionary relationships of modern human remains in Southeast Asia and Oceania. It can be expected that systematic direct dating of human fossils from this area will lead to further revisions of our understanding of modern human evolution.

Electron spin resonance dating of South Australian megafauna sites

In recent years, there has been much debate about the timing of the Late Pleistocene extinction of the Australian megafauna. Some studies postulated a rapid, continental-wide extinction at around 46 000 years ago and that the arrival of humans in Australia, rather than climatic fluctuations, was the main cause for the demise of the megafauna. We have applied electron spin resonance (ESR) dating to a series of teeth from megafauna sites in South Australia, where young ages were expected. During this study, a number of unexpected problems were encountered. These were mainly related to the fact that ESR age assessments on fossil teeth are critically dependent on a realistic reconstruction of the post-mortem uranium uptake into the dental tissues. At virtually all sites, conventional, routine ESR dating, based on the parametric early and linear U-uptake models, would have led to grossly erroneous results. Most teeth were analysed for U-series isotopes with laser ablation ICP-MS, and the results were used to calculate combined U-series ESR age estimates. Only one of the 24 teeth analysed conformed to the commonly applied early and linear U-uptake models. At one of the sites, we found for the first time clear evidence of uranium leaching from dentine. Detailed laser ablation scans revealed that, in contrast to large mammals outside Australia, marsupial tooth enamel does not seem to contain a barrier layer close to the outer surface that blocks uranium diffusion into the enamel. As a consequence, uranium migrates into the enamel layer from both the outside and the inside via the dentine, which makes marsupial teeth generally less well suited for ESR dating. It was particularly difficult to obtain age estimates for the site of Black Creek Swamp, where the sediments contained extreme U-series disequilibrium, and the teeth had unexpectedly accumulated very high U-concentrations (up to 700 ppm in dentine) within a few thousand years. Although most of the sites contained reworked teeth, none of the samples yielded age estimates that were significantly younger than the proposed extinction window of about 40 000–51 000 years.

An early modern human presence in Sumatra 73,000–63,000 years ago

Genetic evidence for anatomically modern humans (AMH) out of Africa before 75 thousand years ago (ka) and in island southeast Asia (ISEA) before 60 ka (93–61 ka) predates accepted archaeological records of occupation in the region. Claims that AMH arrived in ISEA before 60 ka (ref. 4) have been supported only by equivocal or non-skeletal evidence. AMH evidence from this period is rare and lacks robust chronologies owing to a lack of direct dating applications, poor preservation and/or excavation strategies and questionable taxonomic identifications. Lida Ajer is a Sumatran Pleistocene cave with a rich rainforest fauna associated with fossil human teeth. The importance of the site is unclear owing to unsupported taxonomic identification of these fossils and uncertainties regarding the age of the deposit, therefore it is rarely considered in models of human dispersal. Here we reinvestigate Lida Ajer to identify the teeth confidently and establish a robust chronology using an integrated dating approach. Using enamel–dentine junction morphology, enamel thickness and comparative morphology, we show that the teeth are unequivocally AMH. Luminescence and uranium-series techniques applied to bone-bearing sediments and speleothems, and coupled uranium-series and electron spin resonance dating of mammalian teeth, place modern humans in Sumatra between 73 and 63 ka. This age is consistent with biostratigraphic estimations, palaeoclimate and sea-level reconstructions, and genetic evidence for a pre-60 ka arrival of AMH into ISEA. Lida Ajer represents, to our knowledge, the earliest evidence of rainforest occupation by AMH, and underscores the importance of reassessing the timing and environmental context of the dispersal of modern humans out of Africa.

Confirmation of a late middle Pleistocene age for the Omo Kibish 1 cranium by direct uranium-series dating

While it is generally accepted that modern humans evolved in Africa, the specific physical evidence for that origin remains disputed. The modern-looking Omo 1 skeleton, discovered in the Kibish region of Ethiopia in 1967, was controversially dated at ~130 ka (thousands of years ago) by U-series dating on associated Mollusca, and it was not until 2005 that Ar-Ar dating on associated feldspar crystals in pumice clasts provided evidence for an even older age of ~195 ka. However, questions continue to be raised about the age and stratigraphic position of this crucial fossil specimen. Here we present direct U-series determinations on the Omo 1 cranium. In spite of significant methodological complications, which are discussed in detail, the results indicate that the human remains do not belong to a later intrusive burial and are the earliest representative of anatomically modern humans. Given the more archaic morphology shown by the apparently contemporaneous Omo 2 calvaria, we suggest that direct U-series dating is applied to this fossil as well, to confirm its age in relation to Omo 1.

Late-Holocene climatic variability indicated by three natural archives in arid southern Australia:

Three terrestrial climate proxies are used to investigate the evolution of Holocene palaeoenvironments in southern central Australia, all of which present a coherent record of palaeohydrology. Single-grain optically stimulated luminescence from sediments supplemented by 14C from charcoal and lacustrine shells was obtained to date shoreline deposits (Lake Callabonna) and the adjacent Mt Chambers Creek alluvial fan. Our findings are complemented by a U/Th-based record of speleothem growth in the Mt Chambers Creek catchment, which we interpret to reflect increased precipitation. Together, these archives shed light on the timing of, and possible sources of water for, Holocene pluvial intervals. We identified several phases of elevated lake levels dated at ~5.8–5.2, 4.5, 3.5–2.7 and 1 kyr, most of which correspond to fluvial activity resulting from increased precipitation in the adjacent ranges. The enhanced hydrology during phases of the late Holocene likely increased the reliability of resources for regional human populations during a time of reduced winter rainfall. When considered within the framework of the current understanding of Holocene palaeoclimate in central Australia, our data suggest that the pattern of landscape response was broadly synchronous with larger scale climatic variability and punctuated by pluvial periods greater than today.

Naturalism, Nature and Questions of Style in Jinsha River Rock Art, Northwest Yunnan, China

The naturalistic rock art of Yunnan Province is poorly known outside of China despite two decades of investigation by local researchers. The authors report on the first major international study of this art, its place in antiquity and its resemblance to some of the rock art of Europe, southern Africa and elsewhere. While not arguing a direct connection between China, Europe and other widely separated places, this article suggests that rock-art studies about the nature of style, culture contact and the transmission of iconography across space and time need to take better account of the results of neuroscience research, similar economic/ecological circumstances and the probability of independent invention.

The first Australian synchrotron powder diffraction analysis of pigment from a Wandjina motif in the Kimberley, Western Australia

Abstract We report the identification of minerals in stratified paint layers from a Wandjina motif in the central Kimberley region, Western Australia, via synchrotron powder diffraction. Interpreting our findings with reference to previous pigment characterisations of Wandjina motifs, we outline the potential of this method for rock art investigations. We particularly highlight the implications of successful major and minor phase identification in very small (~3 µg) pigment samples. The results of this pilot study show that crystallographic data is critical in helping to separate environmental/cultural signatures from post-depositional processes within anthropogenically applied pigments. In Wandjina rock art, crystallography facilitates the examination of the cultural context of rock art production within an assemblage ethnographically known to have undergone regular, ritual repainting.