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.

Increased risk of hospital admission for dehydration or heat-related illness after initiation of medicines: a sequence symmetry analysis.

WHAT IS KNOWN AND OBJECTIVE: Although several studies have identified factors which increase the risk of heat-related illness, few have assessed the contribution of medicines. To address this knowledge gap, our study aimed to assess the risk of hospital admission for dehydration or other heat-related illness following initiation of medicines. METHODS: We conducted a retrospective analysis using prescription event symmetry analysis (PESA) of 6700 veterans with incident hospital admission for dehydration or heat-related illness (ICD-10-AM codes E86, X30, T67), between 1 January 2001 and 30 June 2013. The main outcome measure was first ever hospital admission for dehydration or heat-related illness following initiation of commonly used medicines. RESULTS AND DISCUSSION: A significantly higher risk of incident hospital admission for dehydration or heat-related illness was observed following initiation of anticoagulants, cardiovascular medicines, NSAIDs, antipsychotics, antidepressants and anticholinergic agents. The risk of hospital admission for dehydration or heat-related illness ranged from 1·17 (SSRIs) to 2·79 (ACEI plus diuretic combination product). No significant association was observed between initiation of anticonvulsants, anti-Parkinson's agents, hypnotics, anxiolytics or antihistamines and hospital admission for dehydration or heat-related illness. WHAT IS NEW AND CONCLUSION: Many commonly used medicines were found to be associated with increased risk of hospitalization for dehydration or heat-related illness. Initiation of ACE inhibitors in combination with diuretics had the highest risk. Prescribers and patients should be aware of the potential for medicines to be associated with increased risk of dehydration and heat-related illness.

Medicines can affect thermoregulation and accentuate the risk of dehydration and heat-related illness during hot weather.

WHAT IS KNOWN AND OBJECTIVE: Hot days are increasingly common and are often associated with increased morbidity and mortality, especially in the elderly. Most heat-related illness and heat-related deaths are preventable. COMMENT: Medicines may accentuate the risk of dehydration and heat-related illness, especially in elderly people taking multiple medicines, through the following mechanisms: diuresis and electrolyte imbalance, sedation and cognitive impairment, changed thermoregulation, reduced thirst recognition, reduced sweat production, and hypotension and reduced cardiac output. WHAT IS NEW AND CONCLUSION: Commonly used medicines that may significantly increase the risk include diuretics, especially when combined with an angiotensin converting enzyme (ACE) inhibitor or an angiotensin II receptor blocker (ARB), anticholinergics and psychotropics. Initiation of individualized preventive measures prior to the start of the hot weather season, which includes a review of the patient and their medicines to identify thermoregulatory issues, may reduce the risk of heat-related illness or death.

Preface: research at Liang Bua, Flores, Indonesia.

Excavations at Liang Bua, Flores, Indonesia, have yielded evidence for an endemic human species, Homo floresiensis, a population that occupied the cave between approximately 95-17ka. This discovery has major implications for early hominin evolution and dispersal in Africa and Asia, attracting worldwide interest. This preface describes the rationale for the excavations in historical, geographical, and wider research contexts, as well as the methods used. It also introduces the other papers on aspects of Liang Bua research that feature in this edition of the Journal of Human Evolution.

The evolving landscape and climate of western Flores: an environmental context for the archaeological site of Liang Bua.

The rapidly changing landscape of the eastern Indonesian archipelago has evolved at a pace dictated by its tropical climate and its geological and tectonic history. This has produced accelerated karstification, flights of alluvial terraces, and complex, multi-level cave systems. These cave systems sometimes contain a wealth of archaeological evidence, such as the almost complete skeleton of Homo floresiensis found at the site of Liang Bua in western Flores, but this information can only be understood in the context of the geomorphic history of the cave, and the more general geological, tectonic, and environmental histories of the river valley and region. Thus, a reconstruction of the landscape history of the Wae Racang valley using speleothems, geological structure, tectonic uplift, karst, cave, and terrace development, provides the necessary evidence to determine the formation, age, evolution, and influences on the site. This evidence suggests that Liang Bua was formed as two subterranean chambers approximately 600ka, but could not be occupied until approximately 190ka when the Wae Racang wandered to the southern side of the valley, exposing the chamber and depositing alluvial deposits containing artifacts. During the next approximately 190k.yr., the chambers coalesced and evolved into a multi-level and interconnected cave that was subjected to channel erosion and pooling events by the development of sinkholes. The domed morphology of the front chamber accumulated deep sediments containing well stratified archaeological and faunal remains, but ponded water in the chamber further prevented hominin use of the cave until approximately 100ka. These chambers were periodically influenced by river inundation and volcanic activity, whereas the area outside the cave was greatly influenced by glacial phases, which changed humid forest environments into grassland environments. This combined evidence has important implications for the archaeological interpretation of the site.

Geochronology of cave deposits at Liang Bua and of adjacent river terraces in the Wae Racang valley, western Flores, Indonesia: a synthesis of age estimates for the type locality of Homo floresiensis.

A robust timeframe for the extant cave deposits at Liang Bua, and for the river terraces in the adjoining Wae Racang valley, is essential to constrain the period of existence and time of extinction of Homo floresiensis and other biota that have been excavated at this hominin type locality. Reliable age control is also required for the variety of artifacts excavated from these deposits, and to assist in environmental reconstructions for this river valley and for the region more broadly. In this paper, we summarize the available geochronological information for Liang Bua and its immediate environs, obtained using seven numerical-age methods: radiocarbon, thermoluminescence, optically- and infrared-stimulated luminescence (collectively known as optical dating), uranium-series, electron spin resonance, and coupled electron spin resonance/uranium-series. We synthesize the large number of numerical age determinations reported previously and present additional age estimates germane to questions of hominin evolution and extinction.

Reconstructing the geomorphic history of Liang Bua, Flores, Indonesia: a stratigraphic interpretation of the occupational environment.

Liang Bua, in Flores, Indonesia, was formed as a subterranean chamber over 600ka. From this time to the present, a series of geomorphic events influenced the structure of the cave and cave deposits, creating a complex stratigraphy. Within these deposits, nine main sedimentary units have been identified. The stratigraphic relationships between these units provide the evidence needed to reconstruct the geomorphic history of the cave. This history was dominated by water action, including slope wash processes, channel formation, pooling of water, and flowstone precipitation, which created waterfalls, cut-and-fill stratigraphy, large pools of water, and extensive flowstone cappings. The reconstructed sequence of events over the last 190k.yr. has been summarized by a series of time slices that demonstrate the nature of the occupational environment in Liang Bua. The earliest artifacts at the site, dated to approximately 190ka, testify to hominin presence in the area, but the reconstructions suggest that occupation of the cave itself may not have been possible until after approximately 100ka. At approximately 95ka, channel erosion of a basal unit, which displays evidence of deposition in a pond environment, created a greater relief on the cave floor, and formed remanent areas of higher ground that later became a focus for hominin occupation from 74-61ka by the west wall and in the center of the cave, and from approximately 18-17ka by the east wall. These zones have been identified according to the sloping nature of the stratigraphy and the distribution of artifacts, and their locations have implications for the archaeological interpretation of the site.

Age and biostratigraphic significance of the Punung Rainforest Fauna, East Java, Indonesia, and implications for Pongo and Homo.

The Punung Fauna is a key component in the biostratigraphic sequence of Java. It represents the most significant faunal turnover on the island in the last 1.5 million years, when Stegodon and other archaic mammal species characteristic of earlier Faunal stages were replaced by a fully modern fauna that included rainforest-dependent species such as Pongo pygmaeus (orangutan). Here, we report the first numerical ages for the Punung Fauna obtained by luminescence and uranium-series dating of the fossil-bearing deposits and associated flowstones. The Punung Fauna contained in the dated breccia is of early Last Interglacial age (between 128+/-15 and 118+/-3 ka). This result has implications for the age of the preceding Ngandong Fauna, including Homo erectus remains found in the Ngandong Terrace, and for the timing of Homo sapiens arrival in Southeast Asia, in view of claims for a modern human tooth associated with the Punung breccia.

Further evidence for small-bodied hominins from the Late Pleistocene of Flores, Indonesia.

Homo floresiensis was recovered from Late Pleistocene deposits on the island of Flores in eastern Indonesia, but has the stature, limb proportions and endocranial volume of African Pliocene Australopithecus. The holotype of the species (LB1), excavated in 2003 from Liang Bua, consisted of a partial skeleton minus the arms. Here we describe additional H. floresiensis remains excavated from the cave in 2004. These include arm bones belonging to the holotype skeleton, a second adult mandible, and postcranial material from other individuals. We can now reconstruct the body proportions of H. floresiensis with some certainty. The finds further demonstrate that LB1 is not just an aberrant or pathological individual, but is representative of a long-term population that was present during the interval 95-74 to 12 thousand years ago. The excavation also yielded more evidence for the depositional history of the cave and for the behavioural capabilities of H. floresiensis, including the butchery of Stegodon and use of fire.

A theoretical investigation of alpha-carbon kinetic isotope effects and their relationship to the transition-state structure of S(N)2 reactions.

[reaction: see text] The transition structures and alpha-carbon 12C/13C kinetic isotope effects for 22 S(N)2 reactions between methyl chloride and a wide variety of nucleophiles have been calculated using the B1LYP/aug-cc-pVDZ level of theory. Anionic, neutral, and radical anion nucleophiles were used to give a wide range of S(N)2 transition states so the relationship between the magnitude of the alpha-carbon kinetic isotope effect and transition-state structure could be determined. The results suggest that the alpha-carbon 12C/13C kinetic isotope effects for S(N)2 reactions will be large (near the experimental maximum) and that the curve relating the magnitude of the KIE to the percent transfer of the alpha-carbon from the nucleophile to the leaving group in the transition state has a broad maximum. This means very similar KIEs will be found for early, symmetric, and late transition states and that one cannot use the magnitude of these KIEs to estimate transition-state structure.

Archaeology and age of a new hominin from Flores in eastern Indonesia.

Excavations at Liang Bua, a large limestone cave on the island of Flores in eastern Indonesia, have yielded evidence for a population of tiny hominins, sufficiently distinct anatomically to be assigned to a new species, Homo floresiensis. The finds comprise the cranial and some post-cranial remains of one individual, as well as a premolar from another individual in older deposits. Here we describe their context, implications and the remaining archaeological uncertainties. Dating by radiocarbon (14C), luminescence, uranium-series and electron spin resonance (ESR) methods indicates that H. floresiensis existed from before 38,000 years ago (kyr) until at least 18 kyr. Associated deposits contain stone artefacts and animal remains, including Komodo dragon and an endemic, dwarfed species of Stegodon. H. floresiensis originated from an early dispersal of Homo erectus (including specimens referred to as Homo ergaster and Homo georgicus) that reached Flores, and then survived on this island refuge until relatively recently. It overlapped significantly in time with Homo sapiens in the region, but we do not know if or how the two species interacted.

A new method of determining chlorine kinetic isotope effects.

Two methods have been used to measure the chlorine leaving group kinetic isotope effect for the S(N)2 reduction of benzyl chloride to toluene by sodium borohydride in DMSO at 30.000 °C. The reaction was monitored by titrating the unreacted borohydride ion. One method involved determining the chlorine isotope effect using the classical IRMS method, which requires the conversion of the chloride ions into gaseous methyl chloride that is analyzed in an isotope ratio mass spectrometric analyses (Hill, J. W.; Fry, A. J. Am. Chem. Soc. 1962, 84, 2763. Taylor, J. W.; Grimsrud, E. P. Anal. Chem. 1969, 41, 805.). Two different measurements using this method yielded isotope effects of k(35)/k(37) = 1.007 19 ± 0.000 19 and 1.007 64 ± 0.000 19. The second method was a new technique where the ratio of the chlorine isotopes was obtained by fast atom bombardment mass spectrometry on the silver chloride recovered from the reaction, i.e., from the first step in the classical procedure. Therefore, the new method is much simpler and avoids the time-consuming preparation, purification, and recovery of the gaseous methyl chloride. Although the experimental error is larger (k(35)/k(37) = 1.008 03 ± 0.00 10 and 1.008 02 ± 0.000 65) when the new technique is used to analyze the silver chloride samples from the same set of experiments that were used to measure the isotope effect by the classical method, the chlorine isotope effect found by the two methods is identical within experimental error. This large chlorine kinetic isotope effect indicates there is considerable C(α)-Cl bond rupture in the S(N)2 transition state.