Cultural Incubators and Spread of Innovation

Several forms of social learning rely on the direct or indirect evaluation of the fitness of cultural traits. Here we argue, via a simple agent-based model, that payoff uncertainty, that is the correlation between a trait and the signal used to evaluate its fitness, plays a pivotal role in the spread of beneficial innovation. More specifically, we examine how this correlation affects the evolutionary dynamics of different forms of social learning and how each can generate divergent historical trajectories depending on the size of the sample pool. In particular, we demonstrate that social learning by copying the best model is particularly susceptible to a sampling effect caused by the interaction of payoff uncertainty, the number of models sampled (the sample pool) and the frequency with which a trait is present in the population. As a result, we identify circumstances in which smaller sample pools can act as ‘cultural incubators’ that promote the spread of innovations, while more widespread sampling of the population actually retards the rate of cultural evolution

Modelling Demic and Cultural Diffusion - An Introduction

Identifying the processes by which human cultures spread across different populations is one of the most topical objectives shared amongst different fields of study. Seminal works have analysed a variety of data and attempted to determine whether empirically observed patterns are the result of demic and/or cultural diffusion. This special issue collects papers exploring several themes (from modes of cultural transmission to drivers of dispersal mechanisms) and contexts (from the Neolithic in Europe to the spread of computer programming languages), which offer new insights that will augment the theoretical and empirical basis for the study of demic and cultural diffusion. In this introduction we outline the state of art in the modelling of these processes, briefly discuss the pros and cons of two of the most commonly used frameworks (i.e. equation-based models and agent-based models), and summarise the significance of each paper published in this special issue

The importance of wild resources as a reflection of the resilience and changing nature of early agricultural systems in East Asia and Europe

We examine the changing importance of wild starch rich plant staples, predominantly tree nuts, in early agricultural societies in East Asia and Europe, focusing on Korea, Japan, and Britain. A comparative review highlights variations in the importance of wild plant staples compared to domesticated crops. The Korean Middle to Late Chulmun periods (c. 3,500–1,500 BC) was characterized by a high reliance on nuts alongside millet. This declines with the transition to rice agriculture, but remains significant during the Mumun period (c. 1,500–300 BC). In Japan, the arrival of rice and millets in the Yayoi Period (c. 1,000 BC−250 AD) saw continued evidence for high levels of reliance on wild resources, which declines only in the Kofun and early historical periods. In Early Neolithic Britain (c. 4,000–3,300 BC) cereal agriculture is accompanied by high evidence for wild plant foods. But during the Middle to Late Neolithic (3,300–c. 2,400/2,200 BC) cereals were abandoned on the mainland with hazelnuts becoming a prominent plant staple. Agriculture returned in the second half of the 3rd millennium BC, followed by a strong decline in wild plant food use during the Middle to Late Bronze Age (1,700–700 BC). Such patterns have previously been attributed to the slow adoption of farming by indigenous peoples, with a continued reliance on wild resources. In light of evidence demonstrating that the dispersal of agriculture was largely driven by a mixture of demic-diffusion and introgression of hunter-gatherers into agricultural groups, a reinterpretation of the role of wild foods is needed. It is argued that the relative importance of wild plant staples provides an indicator of the stability and dependability of agricultural and social systems. A heavy reliance on wild foods in early agricultural societies is tied to the slow adaptation of domesticated crops to new environments, where agricultural and social landscapes are yet to be firmly established, and social systems that could mitigate for poor harvests and storage were often absent. The retained lengthy persistence of wild plant staples in East Asian subsistence systems compared to the British Isles likely reflects differences in the ecological and labor demands for rice compared to Western Asiatic cereals

Summed Probability Distribution of 14C Dates Suggests Regional Divergences in the Population Dynamics of the Jomon Period in Eastern Japan.

Recent advances in the use of summed probability distribution (SPD) of calibrated 14C dates have opened new possibilities for studying prehistoric demography. The degree of correlation between climate change and population dynamics can now be accurately quantified, and divergences in the demographic history of distinct geographic areas can be statistically assessed. Here we contribute to this research agenda by reconstructing the prehistoric population change of Jomon hunter-gatherers between 7,000 and 3,000 cal BP. We collected 1,433 14C dates from three different regions in Eastern Japan (Kanto, Aomori and Hokkaido) and established that the observed fluctuations in the SPDs were statistically significant. We also introduced a new non-parametric permutation test for comparing multiple sets of SPDs that highlights point of divergences in the population history of different geographic regions. Our analyses indicate a general rise-and-fall pattern shared by the three regions but also some key regional differences during the 6th millennium cal BP. The results confirm some of the patterns suggested by previous archaeological studies based on house and site counts but offer statistical significance and an absolute chronological framework that will enable future studies aiming to establish potential correlation with climatic changes.Marie-Curie Intra-European Fellowship (Grant ID: 625863), SimulPast Project (Consolider-Ingenio CSD2010-00034)This is the final version of the article. It first appeared from the Public Library of Science via http://dx.doi.org/10.1371/journal.pone.015480

Approximate Bayesian Computation of radiocarbon and paleoenvironmental record shows population resilience on Rapa Nui (Easter Island).

Examining how past human populations responded to environmental and climatic changes is a central focus of the historical sciences. The use of summed probability distributions (SPD) of radiocarbon dates as a proxy for estimating relative population sizes provides a widely applicable method in this research area. Paleodemographic reconstructions and modeling with SPDs, however, are stymied by a lack of accepted methods for model fitting, tools for assessing the demographic impact of environmental or climatic variables, and a means for formal multi-model comparison. These deficiencies severely limit our ability to reliably resolve crucial questions of past human-environment interactions. We propose a solution using Approximate Bayesian Computation (ABC) to fit complex demographic models to observed SPDs. Using a case study from Rapa Nui (Easter Island), a location that has long been the focus of debate regarding the impact of environmental and climatic changes on its human population, we find that past populations were resilient to environmental and climatic challenges. Our findings support a growing body of evidence showing stable and sustainable communities on the island. The ABC framework offers a novel approach for exploring regions and time periods where questions of climate-induced demographic and cultural change remain unresolved

Bayesian analyses question the role of climate in Chulmun demography.

We investigate the relationship between climatic and demographic events in Korea during the Chulmun period (10,000-3,500 cal. BP) by analyzing paleoenvironmental proxies and 14C dates. We focus on testing whether a cooling climate, and its potential negative impact on millet productivity around the mid 5th-millennium cal. BP, triggered the population decline suggested by the archaeological record. We employ a Bayesian approach that estimates the temporal relationship between climatic events and change-points in the rate of growth in human population as inferred from radiocarbon time frequency data. Our results do not support the climate-induced population decline hypothesis for three reasons. First, our Bayesian analyses suggest that the cooling event occurred after the start of the population decline inferred from the radiocarbon time-frequency record. Second, we did not find evidence showing a significant reduction of millet-associated dates occurring during the cooling climate. Third, we detected different magnitudes of decline in the radiocarbon time-frequency data in the inland and coastal regions, indicating that the even if cooling episodes were ultimately responsible of these population 'busts', their impact was most likely distinct between these regions. We discuss our results highlighting the long tradition of mobility-based subsistence strategy in coastal regions as a potential factor contributing to the regional differences we were able to detect

Elastic scattering and total reaction cross sections for the 8Li + 12C system

The elastic-scattering angular distribution for 8Li on 12C has been measured at ELAB=23.9 MeV with 8Li radioactive nuclear beam produced by the Radioactive Ion Beams in Brazil facility. This angular distribution was analyzed in terms of optical-model with Woods-Saxon and double-folding São Paulo potential. The roles of the breakup and inelastic channels were also investigated with cluster folding and deformed potentials, respectively, through coupled-channels calculations. The angular distribution for the proton-transfer 12C(8Li,9Be)11B reaction was also measured at the same energy. The spectroscopic factor for the 9Be|8Li+p bound system was obtained and compared with shell-model calculations and with other experimental values. Total reaction cross sections for the present system were also extracted from the elastic-scattering analysis. A systematic of the reduced reaction cross sections obtained from the present and published data on 6,7,8Li isotopes on 12C was performed as a function of energy

Interpretation and the Constraints on International Courts

This paper argues that methodologies of interpretation do not do what they promise – they do not constrain interpretation by providing neutral steps that one can follow in finding out a meaning of a text – but nevertheless do their constraining work by being part of what can be described as the legal practice

Extensive unusual lesions on a large number of immersed human victims found to be from cookiecutter sharks (Isistius spp.): an examination of the Yemenia plane crash.

Accurate determination of the origin and timing of trauma is key in medicolegal investigations when the cause and manner of death are unknown. However, distinction between criminal and accidental perimortem trauma and postmortem modifications can be challenging when facing unidentified trauma. Postmortem examination of the immersed victims of the Yemenia airplane crash (Comoros, 2009) demonstrated the challenges in diagnosing extensive unusual circular lesions found on the corpses. The objective of this study was to identify the origin and timing of occurrence (peri- or postmortem) of the lesions.A retrospective multidisciplinary study using autopsy reports (n = 113) and postmortem digital photos (n = 3 579) was conducted. Of the 113 victims recovered from the crash, 62 (54.9 %) presented unusual lesions (n = 560) with a median number of 7 (IQR 3 ∼ 13) and a maximum of 27 per corpse. The majority of lesions were elliptic (58 %) and had an area smaller than 10 cm2 (82.1 %). Some lesions (6.8 %) also showed clear tooth notches on their edges. These findings identified most of the lesions as consistent with postmortem bite marks from cookiecutter sharks (Isistius spp.). It suggests that cookiecutter sharks were important agents in the degradation of the corpses and thus introduced potential cognitive bias in the research of the cause and manner of death. A novel set of evidence-based identification criteria for cookiecutter bite marks on human bodies is developed to facilitate more accurate medicolegal diagnosis of cookiecutter bites.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s00414-016-1449-