Human influence on distribution and extinctions of the late Pleistocene Eurasian megafauna

Late Pleistocene extinctions are of interest to paleontological and anthropological research. In North America and Australia, human occupation occurred during a short period of time and overexploitation may have led to the extinction of mammalian megafauna. In northern Eurasia megafaunal extinctions are believed to have occurred over a relatively longer period of time, perhaps as a result of changing environmental conditions, but the picture is much less clear. To consider megafaunal extinction in Eurasia, we compare differences in the geographical distribution and commonness of extinct and extant species between paleontological and archaeological localities from the late middle Pleistocene to Holocene. Purely paleontological localities, as well as most extinct species, were distributed north of archaeological sites and of the extant species, suggesting that apart from possible differences in adaptations between humans and other species, humans could also have a detrimental effect on large mammal distribution. However, evidence for human overexploitation applies only to the extinct steppe bison Bison priscus. Other human-preferred species survive into the Holocene, including Rangifer tarandus, Equus ferus, Capreolus capreolus, Cervus elaphus, Equus hemionus, Saiga tatarica, and Sus scrofa. Mammuthus primigenius and Megaloceros giganteus were rare in archaeological sites. Carnivores appear little influenced by human presence, although they become rarer in Holocene archaeological sites. Overall, the data are consistent with the conclusion that humans acted as efficient hunters selecting for the most abundant species. Our study supports the idea that the late Pleistocene extinctions were environmentally driven by climatic changes that triggered habitat fragmentation, species range reduction, and population decrease, after which human interference either by direct hunting or via indirect activities probably became critical.     

Did the historical range of the European bison (<Emphasis Type="Italic">Bison bonasus</Emphasis> L.) extend further south?—a new finding from the Yenikapı Metro and Marmaray excavation,Turkey

The origin of the European bison (Bison bonasus, Linnaeus, 1758) has been widely discussed and investigated in recent years. The species had a wide historic geographic distribution throughout the European continent during the middle and late Holocene, ranging from France in the west to the Caucasus in the east. However, archaeological evidence is needed to resolve the southern extent of the European bison distribution. We discovered one bison skull fragment during archaeological excavations in 2008 in the area of Yenikap? Metro and Marmaray (Turkey). Radiocarbon dating indicated the skull was deposited during the Byzantine period (seventh to eighth century AD). Mitochondrial genome analyses provided clear evidence that the skull was from a European bison. This is the first unambiguous evidence of the presence of this species in southeastern Europe during Byzantine times, which validates the historical written records of a potentially wider range of the European bison in historical times.     

Contraception of bison by GnRH vaccine: a possible means of decreasing transmission of brucellosis in bison

Preventing pregnancy in brucellosis-infected bison (Bison bison) provides a potential means of preventing transmission of disease. To determine whether a gonadotropin-releasing hormone (GnRH) vaccine was effective in reducing pregnancy in bison and to study the safety of injecting GnRH in pregnant bison, a study was conducted at the Idaho Fish and Game Wildlife Health Laboratory in Caldwell, Idaho (USA). Four pregnant and two nonpregnant female bison were given a single injection of GnRH vaccine, and five pregnant adult females were given a sham injection that contained only adjuvant. Three of the GnRH-vaccinated bison that were pregnant at the time of vaccination delivered healthy calves. One treated bison had dystocia that resulted in a dead calf. All control bison delivered healthy calves. After calving, females of both groups were exposed to two bulls. Treated bison were palpated 6 wk after exposure to the bulls, and blood was drawn for pregnancy-specific protein B analysis. The six treated bison were not pregnant. The sham-treated bison became pregnant and delivered viable calves. This study demonstrates that a single dose of GnRH vaccine is effective in preventing pregnancy in female bison for at least 1 yr.     

Holocene radiocarbon-dated sites in northeastern Siberia: issues of temporal frequency, reservoir age, and human-nature interaction

The existing corpus of data on radiocarbon dates for Holocene sites in Northeastern Siberia was used as proxy to reconstruct the chronology of human occupation of the region. The problem of reservoir age correction in the Bering Sea region complicated this task and this issue needs to be solved in order to obtain more reliable age determinations for coastal archaeological sites. Using a chronology built after excluding the questionable dates from the database, the major patterns of human population dynamics and their possible correlation with climatic fluctuations were examined. No direct relationship appears to exist between these two processes. Additional archaeological and paleo environmental work needs to be carried out in this region of the North.     

Climate change and evolving human diversity in Europe during the last glacial

A link between climate change and human evolution during the Pleistocene has often been assumed but rarely tested. At the macro-evolutionary level Foley showed for hominids that extinction, rather than speciation, correlates with environmental change as recorded in the deep sea record. Our aim is to examine this finding at a smaller scale and with high-resolution environmental and archaeological archives. Our interest is in changing patterns of human dispersal under shifting Pleistocene climates during the last glacial period in Europe. Selecting this time frame and region allows us to observe how two hominid taxa, Neanderthals and Crô-Magnons, adapted to climatic conditions during oxygen isotope stage 3. These taxa are representative of two hominid adaptive radiations, termed terrestrial and aquatic, which exhibited different habitat preferences but similar tolerances to climatic factors. Their response to changing ecological conditions was predicated upon their ability to extend their societies in space and time. We examine this difference further using a database of all available radiocarbon determinations from western Europe in the late glacial. These data act as proxies for population history, and in particular the expansion and contraction of regional populations as climate changed rapidly. Independent assessment of these processes is obtained from the genetic history of Europeans. The results indicate that climate affects population contraction rather than expansion. We discuss the consequences for genetic and cultural diversity which led to the legacy of the Ice Age: a single hominid species, globally distributed.     

Reconstructing range dynamics and range fragmentation of European bison for the last 8000 years

Aim Understanding what constituted species’ ranges prior to large‐scale human influence, and how past climate and land use change have affected range dynamics, provides conservation planners with important insights into how species may respond to future environmental change. Our aim here was to reconstruct the Holocene range of European bison (Bison bonasus) by combining a time‐calibrated species distribution models (SDM) with a dynamic vegetation model. Location Europe. Method We used European bison occurrences from the Holocene in a maximum entropy model to assess bison range dynamics during the last 8000 years. As predictors, we used bioclimatic variables and vegetation reconstructions from the generalized dynamic vegetation model LPJ‐GUESS. We compared our range maps with maps of farmland and human population expansion to identify the main species range constraints. Results The Holocene distribution of European bison was mainly determined by vegetation patterns, with bison thriving in both broadleaved and coniferous forests, as well as by mean winter temperature. The heartland of European bison was in Central and Eastern Europe, whereas suitable habitat in Western Europe was scarce. While environmentally suitable regions were overall stable, the expansion of settlements and farming severely diminished available habitat. Main conclusions European bison habitat preferences may be wider than previously assumed, and our results suggest that the species had a more eastern and northern distribution than previously reported. Vegetation and climate transformation during the Holocene did not affect the bison’s range substantially. Conversely, human population growth and the spread of farming resulted in drastic bison habitat loss and fragmentation, likely reaching a tipping point during the last 1000 years. Combining SDM and dynamic vegetation models can improve range reconstructions and projections, and thus help to identify resilient conservation strategies for endangered species.     

Health risks associated with wild animal translocation: a case of the European bison and an alien parasite

Introducing an animal into a new location could be hazardous in the form of disease transmission, especially with respect to infections that are often overlooked. Such introduced infectious agents, including parasitic ones, then pose potential danger to the native animal population. Within the conservation program, the European bison was introduced into many European countries. However, this largest European herbivore was recognized as a new host for an invasive parasitic nematode, Ashworthius sidemi, in Poland in 1998. Since then, the prevalence of this non-native parasite in Poland has increased not only in bison but also in other wild ruminants. In 2011 five European bison individuals were transported from Poland to the Czech Republic. In the current study, we examined the gastrointestinal tracts of two European bison and two red deer culled in the ?idlov game reserve. A. sidemi was identified in all investigated animals using both morphological and molecular methods; infection intensity was higher in bison than in deer. Our findings represent the first record of this invasive parasite in European bison at the Czech territory. The results of this study indicate changes in epidemiological patterns of Ashworthius infections in the climatic condition of Central Europe as well as the need to verify the reliability of ashworthiosis intravital diagnostics. One can expect A. sidemi to spread gradually in the Czech Republic and colonize other native ruminant hosts.     

Population bottlenecks and Pleistocene human evolution

We review the anatomical and archaeological evidence for anearly population bottleneck in humans and bracket the time whenit could have occurred. We outline the subsequent demographicchanges that the archaeological evidence of range expansionsand contractions address, and we examine how inbreeding effectivepopulation size provides an alternative view of past populationsize change. This addresses the question of other, more recent,population size bottlenecks, and we review nonrecombining andrecombining genetic systems that may reflect them. We examinehow these genetic data constrain the possibility of significantpopulation size bottlenecks (i.e., of sufficiently small sizeand/or long duration to minimize genetic variation in autosomaland haploid systems) at several different critical times inhuman history. Different constraints appear in nonrecombiningand recombining systems, and among the autosomal loci most areincompatible with any Pleistocene population size expansions.Microsatellite data seem to show Pleistocene population sizeexpansions, but in aggregate they are difficult to interpretbecause different microsatellite studies do not show the sameexpansion. The archaeological data are only compatible witha few of these analyses, most prominently with data from Aluelements, and we use these facts to question whether the viewof the past from analysis of inbreeding effective populationsize is valid. Finally, we examine the issue of whether inbreedingeffective population size provides any reasonable measure ofthe actual past size of the human species. We contend that ifthe evidence of a population size bottleneck early in the evolutionof our lineage is accepted, most genetic data either lack theresolution to address subsequent changes in the human populationor do not meet the assumptions required to do so validly. Itis our conclusion that, at the moment, genetic data cannot disprovea simple model of exponential population growth following abottleneck 2 MYA at the origin of our lineage and extendingthrough the Pleistocene. Archaeological and paleontologicaldata indicate that this model is too oversimplified to be anaccurate reflection of detailed population history, and thereforewe find that genetic data lack the resolution to validly reflectmany details of Pleistocene human population change. However,there is one detail that these data are sufficient to address.Both genetic and anthropological data are incompatible withthe hypothesis of a recent population size bottleneck. Suchan event would be expected to leave a significant mark acrossnumerous genetic loci and observable anatomical traits, butwhile some subsets of data are compatible with a recent populationsize bottleneck, there is no consistently expressed effect thatcan be found across the range where it should appear, and thisabsence disproves the hypothesis.     

Reproductive success of bison bulls (Bison bison bison) in semi-natural conditions

Sexual size dimorphism has been related to a high variance in male reproductive success. Research on American bison (Bison bison bison), a species that shows moderate sexual dimorphism, has put forward the assumption that under wild conditions the largest part of the female herd is bred by a limited number of males. Thus far, this hypothesis has never been supported by genetic data. The aim of this study is therefore to test the hypothesis of extreme male reproductive variance among bison through the determination of the reproductive success of the bulls in private herds. We analysed genetic paternity in four private herds (n=19, 33, 39 and 54) kept under semi-natural conditions. By analysing blood, hair and tissue samples, using 8-10 polymorphic microsatellites, the reproductive success of the bulls was quantified. Additional genetic data were gathered through a survey distributed among bison breeders with private herds over the world. Results show a highly differential reproductive success for bison males in private herds kept under semi-natural conditions. In each study group, a single male sires at least 70% of the calves. In the survey groups, a single male sires 81-100% of the calves. Only one survey group displayed a deviating pattern showing a more evenly distribution of paternity (28.57, 33.33 and 38.10%) among three same aged subadult males.     

Collective decision‐making promotes fitness loss in a fusion‐fission society

While collective decision‐making is recognised as a significant contributor to fitness in social species, the opposite outcome is also logically possible. We show that collective movement decisions guided by individual bison sharing faulty information about habitat quality promoted the use of ecological traps. The frequent, but short‐lived, associations of bison with different spatial knowledge led to a population‐wide shift from avoidance to selection of agricultural patches over 9 years in and around Prince Albert National Park, Canada. Bison were more likely to travel to an agricultural patch for the first time by following conspecifics already familiar with agricultural patches. Annual adult mortality increased by 12% due to hunting of bison on agricultural lands. Maladaptive social behaviour accordingly was a major force that contributed to a ~50% population decline in less than a decade. In human‐altered landscapes, social learning by group‐living species can lead to fitness losses, particularly in fusion‐fission societies.     

On the importance of being structured: instantaneous coalescence rates and human evolution—lessons for ancestral population size inference?

Most species are structured and influenced by processes that either increased or reduced gene flow between populations. However, most population genetic inference methods assume panmixia and reconstruct a history characterized by population size changes. This is potentially problematic as population structure can generate spurious signals of population size change through time. Moreover, when the model assumed for demographic inference is misspecified, genomic data will likely increase the precision of misleading if not meaningless parameters. For instance, if data were generated under an n-island model (characterized by the number of islands and migrants exchanged) inference based on a model of population size change would produce precise estimates of a bottleneck that would be meaningless. In addition, archaeological or climatic events around the bottleneck''s timing might provide a reasonable but potentially misleading scenario. In a context of model uncertainty (panmixia versus structure) genomic data may thus not necessarily lead to improved statistical inference. We consider two haploid genomes and develop a theory that explains why any demographic model with structure will necessarily be interpreted as a series of changes in population size by inference methods ignoring structure. We formalize a parameter, the inverse instantaneous coalescence rate, and show that it is equivalent to a population size only in panmictic models, and is mostly misleading for structured models. We argue that this issue affects all population genetics methods ignoring population structure which may thus infer population size changes that never took place. We apply our approach to human genomic data.     

Conservation genomics: disequilibrium mapping of domestic cattle chromosomal segments in North American bison populations

Introgressive hybridization is one of the major threats to species conservation, and is often induced by human influence on the natural habitat of wildlife species. The ability to accurately identify introgression is critical to understanding its importance in evolution and effective conservation management of species. Hybridization between North American bison (Bison bison) and domestic cattle (Bos taurus) as a result of human activities has been recorded for over 100 years, and domestic cattle mitochondrial DNA was previously detected in bison populations. In this study, linked microsatellite markers were used to identify domestic cattle chromosomal segments in 14 genomic regions from 14 bison populations. Cattle nuclear introgression was identified in five populations, with an average frequency per population ranging from 0.56% to 1.80%. This study represents the first use of linked molecular markers to examine introgression between mammalian species and the first demonstration of domestic cattle nuclear introgression in bison. To date, six public bison populations have been identified with no evidence of mitochondrial or nuclear domestic cattle introgression, providing information critical to the future management of bison genetic resources. The ability to identify even low levels of introgression resulting from historic hybridization events suggests that the use of linked molecular markers to identify introgression is a significant development in the study of introgressive hybridization across a broad range of taxa.     

Space Use and Movement Patterns in a Semi-Free-Ranging Herd of European Bison (Bison bonasus)

The successful reintroduction and restocking of the European Bison demands a reliable knowledge of the biology of this species. Yet little is known to date about the European bison, and empirical data remains insufficient to set up a reliable plan ensuring the reintroduction, maintenance and survival of populations in habitats that have been largely modified by human activity. Studies of the ecology, social behaviour and management of bison are therefore crucial to the conservation of this species and its cohabitation with humans. To meet these challenges, we focused on movement patterns and space use in a semi-free-ranging herd of European bison living in the Réserve Biologique des Monts-d’Azur (France). Bison spend over 80% of their time foraging and resting; foraging mainly occurs around the artificial feeding sites (i.e., hay racks) or in meadows. The time of day and the presence of snow have no influence on the time budget allocated to each activity. Animals, however, spend more time at the food racks in winter. Bison also spend most of their time in small groups of individuals, confirming the occurrence of both fission-fusion dynamics and sexual segregation in this species. Bison seem to follow a Lévy walk pattern of movement, which is probably related to the geographical distribution and size of food patches in the reserve. The conclusions of this study provide a better understanding of the sociality, life habits and habitat use of bison, and also describe how the provision of hay affects all these behaviours. These results could be useful in the development of tools to select the most suitable habitats for the reintroduction, management and conservation of bison populations.     

The environmental context for the origins of modern human diversity: a synthesis of regional variability in African climate 150,000-30,000 years ago

We synthesize African paleoclimate from 150 to 30 ka (thousand years ago) using 85 diverse datasets at a regional scale, testing for coherence with North Atlantic glacial/interglacial phases and northern and southern hemisphere insolation cycles. Two major determinants of circum-African climate variability over this time period are supported by principal components analysis: North Atlantic sea surface temperature (SST) variations and local insolation maxima. North Atlantic SSTs correlated with the variability found in most circum-African SST records, whereas the variability of the majority of terrestrial temperature and precipitation records is explained by local insolation maxima, particularly at times when solar radiation was intense and highly variable (e.g., 150-75 ka). We demonstrate that climates varied with latitude, such that periods of relatively increased aridity or humidity were asynchronous across the northern, eastern, tropical and southern portions of Africa. Comparisons of the archaeological, fossil, or genetic records with generalized patterns of environmental change based solely on northern hemisphere glacial/interglacial cycles are therefore imprecise.We compare our refined climatic framework to a database of 64 radiometrically-dated paleoanthropological sites to test hypotheses of demographic response to climatic change among African hominin populations during the 150-30 ka interval. We argue that at a continental scale, population and climate changes were asynchronous and likely occurred under different regimes of climate forcing, creating alternating opportunities for migration into adjacent regions. Our results suggest little relation between large scale demographic and climate change in southern Africa during this time span, but strongly support the hypothesis of hominin occupation of the Sahara during discrete humid intervals ∼135-115 ka and 105-75 ka. Hominin populations in equatorial and eastern Africa may have been buffered from the extremes of climate change by locally steep altitudinal and rainfall gradients and the complex and variable effects of increased aridity on human habitat suitability in the tropics. Our data are consistent with hominin migrations out of Africa through varying exit points from ∼140-80 ka.     

Bayesian coalescent inference of past population dynamics from molecular sequences

We introduce the Bayesian skyline plot, a new method for estimating past population dynamics through time from a sample of molecular sequences without dependence on a prespecified parametric model of demographic history. We describe a Markov chain Monte Carlo sampling procedure that efficiently samples a variant of the generalized skyline plot, given sequence data, and combines these plots to generate a posterior distribution of effective population size through time. We apply the Bayesian skyline plot to simulated data sets and show that it correctly reconstructs demographic history under canonical scenarios. Finally, we compare the Bayesian skyline plot model to previous coalescent approaches by analyzing two real data sets (hepatitis C virus in Egypt and mitochondrial DNA of Beringian bison) that have been previously investigated using alternative coalescent methods. In the bison analysis, we detect a severe but previously unrecognized bottleneck, estimated to have occurred 10,000 radiocarbon years ago, which coincides with both the earliest undisputed record of large numbers of humans in Alaska and the megafaunal extinctions in North America at the beginning of the Holocene.     

Late Quaternary Bison Population Changes On The Southern Plains

Abstract

An analysis of faunal lists from 160 archaeological and paleontological sites in the Southern Plains reveals a success of long-term periods of presence and absence of the genus Bison in the region. Two absence periods are from about 6000-5000 B.C. to 2500 B.C. and A.D. 500 to A.D. 1200-1300. These long-term changes seem to indicate a combination of fluctuating bison population densities and range shifts. Certain previously documented prehistoric cultural events in particular subareas ofthe Southern Plains vicinity are examined in light of these data.     

Why are population growth rate estimates of past and present hunter–gatherers so different?

Hunter–gatherer population growth rate estimates extracted from archaeological proxies and ethnographic data show remarkable differences, as archaeological estimates are orders of magnitude smaller than ethnographic and historical estimates. This could imply that prehistoric hunter–gatherers were demographically different from recent hunter–gatherers. However, we show that the resolution of archaeological human population proxies is not sufficiently high to detect actual population dynamics and growth rates that can be observed in the historical and ethnographic data. We argue that archaeological and ethnographic population growth rates measure different things; therefore, they are not directly comparable. While ethnographic growth rate estimates of hunter–gatherer populations are directly linked to underlying demographic parameters, archaeological estimates track changes in the long-term mean population size, which reflects changes in the environmental productivity that provide the ultimate constraint for forager population growth. We further argue that because of this constraining effect, hunter–gatherer populations cannot exhibit long-term growth independently of increasing environmental productivity.This article is part of the theme issue ‘Cross-disciplinary approaches to prehistoric demography’.     

On the number of New World founders: a population genetic portrait of the peopling of the Americas

The founding of New World populations by Asian peoples is the focus of considerable archaeological and genetic research, and there persist important questions on when and how these events occurred. Genetic data offer great potential for the study of human population history, but there are significant challenges in discerning distinct demographic processes. A new method for the study of diverging populations was applied to questions on the founding and history of Amerind-speaking Native American populations. The model permits estimation of founding population sizes, changes in population size, time of population formation, and gene flow. Analyses of data from nine loci are consistent with the general portrait that has emerged from archaeological and other kinds of evidence. The estimated effective size of the founding population for the New World is fewer than 80 individuals, approximately 1% of the effective size of the estimated ancestral Asian population. By adding a splitting parameter to population divergence models it becomes possible to develop detailed portraits of human demographic history. Analyses of Asian and New World data support a model of a recent founding of the New World by a population of quite small effective size.     

Parasites and diseases of bison in Canada IV. Serologic survey for brucellosis in bison in northern Canada

Serum samples collected from 2,365 free-roaming hybrid bison (Bison bison bison x Bison bison athabascae) in Wood Buffalo National Park and adjacent areas in the Northwest Territories were tested for brucellosis during the period 1959 to 1974. A positive reaction was obtained in 739 (31.2%) of the animals tested. The overall effect of brucellosis on this free-roaming bison population is unknown. The authors also dealt with some of the actual and possible consequences of the disease in this population.     

Overwinter survival of carfentanil-immobilized male bison

A problem with studies that examine immobilization-related drug effects on large mammals is that no true control group exists because untreated (non-captured) animals in the same population have not been examined. We present data to show that overwinter survival in male bison (Bison bison) immobilized with carfentanil was the same as untreated bison. This unique experimental design allows us to conclude that the drug had no long-term effect on male bison overwinter survival.