Declining Orangutan Encounter Rates from Wallace to the Present Suggest the Species Was Once More Abundant

BACKGROUND: Bornean orangutans (Pongo pygmaeus) currently occur at low densities and seeing a wild one is a rare event. Compared to present low encounter rates of orangutans, it is striking how many orangutan each day historic collectors like Alfred Russel Wallace were able to shoot continuously over weeks or even months. Does that indicate that some 150 years ago encounter rates with orangutans, or their densities, were higher than now? METHODOLOGY/PRINCIPAL FINDINGS: We test this hypothesis by quantifying encounter rates obtained from hunting accounts, museum collections, and recent field studies, and analysing whether there is a declining trend over time. Logistic regression analyses of our data support such a decline on Borneo between the mid-19th century and the present. Even when controlled for variation in the size of survey and hunting teams and the durations of expeditions, mean daily encounter rates appear to have declined about 6-fold in areas with little or no forest disturbance. CONCLUSIONS/SIGNIFICANCE: This finding has potential consequences for our understanding of orangutans, because it suggests that Bornean orangutans once occurred at higher densities. We explore potential explanations-habitat loss and degradation, hunting, and disease-and conclude that hunting fits the observed patterns best. This suggests that hunting has been underestimated as a key causal factor of orangutan density and distribution, and that species population declines have been more severe than previously estimated based on habitat loss only. Our findings may require us to rethink the biology of orangutans, with much of our ecological understanding possibly being based on field studies of animals living at lower densities than they did historically. Our approach of quantifying species encounter rates from historic data demonstrates that this method can yield valuable information about the ecology and population density of species in the past, providing new insight into species' conservation needs

Persistent Place-Making in Prehistory: the Creation, Maintenance, and Transformation of an Epipalaeolithic Landscape

Most archaeological projects today integrate, at least to some degree, how past people engaged with their surroundings, including both how they strategized resource use, organized technological production, or scheduled movements within a physical environment, as well as how they constructed cosmologies around or created symbolic connections to places in the landscape. However, there are a multitude of ways in which archaeologists approach the creation, maintenance, and transformation of human-landscape interrelationships. This paper explores some of these approaches for reconstructing the Epipalaeolithic (ca. 23,000–11,500 years BP) landscape of Southwest Asia, using macro- and microscale geoarchaeological approaches to examine how everyday practices leave traces of human-landscape interactions in northern and eastern Jordan. The case studies presented here demonstrate that these Epipalaeolithic groups engaged in complex and far-reaching social landscapes. Examination of the Early and Middle Epipalaeolithic (EP) highlights that the notion of “Neolithization” is somewhat misleading as many of the features we use to define this transition were already well-established patterns of behavior by the Neolithic. Instead, these features and practices were enacted within a hunter-gatherer world and worldview

Archaeological discontinuities in the southern hemisphere: A working agenda

This introductory overview presents the frame of research and general goals of the special volume “Archaeological Discontinuities: Comparative Frameworks for the southern hemisphere”. We begin by deconstructing archaeological discontinuities in terms of time and space in order to assess what sort of past phenomena are we dealing with when assessing discontinuities in different scales. It is one of our main contentions that we need theory and data connecting discontinuities as recorded on different analytical scales, thereby contributing to evaluate often-undescribed mechanisms that produce archaeological discontinuities. On this basis, we face the key task of deconstructing archaeological discontinuities from ‘top to bottom’, moving from the averaged material record that is visible in archaeological scale toward the short-term human decisions and interactions that, when occurring cumulatively, produce those discontinuities. Nevertheless, while an understanding of the short-term behavioral mechanisms and social agency behind discontinuities is necessary, it is certainly not sufficient for building a frame in which to make sense of the long-term record. Archaeological discontinuities recorded at different spatial scales require different explanatory mechanisms that can be connected hierarchically. The most productive analytical take here would be to move from the bottom to the top, building from the site or local scales to the regional and continental levels. This strategy provides a solid frame for assessing the genesis of discontinuities at different scales by disentangling the incidence of sampling deficiencies in the field, the selection of samples for chronometric dating, taphonomic biases, the reorganization of mobility and technology, local and regional abandonments, and actual demographic changes. We finish by selecting a few issues that we consider worthy of systematic comparative attention in the years to come. These issues impinge on different levels of theory and methods and can only be pursued with an interdisciplinary focus that encompasses not only archaeology but also ethnography, genetics, linguistics, paleoclimatology and paleoecology. We are convinced that there is much to learn from a comparative perspective in terms of structural similitudes in historical processes across regions and continents. The conceptual structure of a number of debates from South America, Africa, and Australia on is remarkably similar, notwithstanding important differences in terms of chronology and tempo. We look forward to international joint endeavors such as this one that help to formalize questions and data-collecting strategies for the southern drylands and beyond

Making sense of residues on flaked stone artefacts: learning from blind tests

Residue analysis has become a frequently applied method for identifying prehistoric stone tool use. Residues adhering to the stone tool with varying frequencies are interpreted as being the result of an intentional contact with the worked material during use. Yet, other processes during the life cycle of a stone tool or after deposition may leave residues and these residues may potentially lead to misinterpretations. We present a blind test that was designed to examine this issue. Results confirm that production, retouch, prehension, hafting, various incidental contacts during use and deposition may lead to residue depositions that significantly affect the accurateness of identifications of tool-use. All currently applied residue approaches are concerned. We therefore argue for a closer interaction with independent wear studies and a step-wise procedure in which a low magnification of wear traces is used as a first step for selecting potentially used flakes in archaeological contexts. In addition, residue concentrations on a tool's edge should be sufficiently dense before linking them with use