Enrico R. Crema

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.

The chronology of culture: a comparative assessment of European Neolithic dating approaches

Archaeologists have long sought appropriate ways to describe the duration and floruit of archaeological cultures in statistical terms. Thus far, chronological reasoning has been largely reliant on typological sequences. Using summed probability distributions, the authors here compare radiocarbon dates for a series of European Neolithic cultures with their generally accepted ‘standard’ date ranges and with the greater precision afforded by dendrochronology, where that is available. The resulting analysis gives a new and more accurate description of the duration and intensity of European Neolithic cultures.

Cycles of change in Jomon settlement: a case study from eastern Tokyo Bay

Japanese archaeology benefits from the large number of rescue excavations conducted during recent decades that have led to an unparalleled record of archaeological sites. That record is here put to use to interrogate changing settlement patterns in the north-eastern corner of Tokyo Bay during several millennia of the Jomon period (Early, Middle and Late Jomon: 7000–3220 cal BP). Jomon hunter-gatherer occupation is characterised by large numbers of settlements, some of them substantial in size, containing hundreds of individual pit-house residential units. Detailed analysis of the rank-size distribution of these settlements reveals a pattern in which periods of settlement clumping, with few large settlements, alternate with more dispersed settlement patterns on a regular cycle of approximately 600 years. The regularity of this cycle might suggest a correlation with cycles of climatic change, such as Bond events. Closer scrutiny shows, however, that such a correlation is unconvincing and suggests that cyclical change in Jomon settlement patterns may instead be due to other factors.

Size Reduction in Early European Domestic Cattle Relates to Intensification of Neolithic Herding Strategies

Our analysis of over 28,000 osteometric measurements from fossil remains dating between c. 5600 and 1500 BCE reveals a substantial reduction in body mass of 33% in Neolithic central European domestic cattle. We investigate various plausible explanations for this phenotypic adaptation, dismissing climatic change as a causal factor, and further rejecting the hypothesis that it was caused by an increase in the proportion of smaller adult females in the population. Instead we find some support for the hypothesis that the size decrease was driven by a demographic shift towards smaller newborns from sub-adult breeding as a result of intensifying meat production strategies during the Neolithic.

Revealing patterns of cultural transmission from frequency data: equilibrium and non-equilibrium assumptions

A long tradition of cultural evolutionary studies has developed a rich repertoire of mathematical models of social learning. Early studies have laid the foundation of more recent endeavours to infer patterns of cultural transmission from observed frequencies of a variety of cultural data, from decorative motifs on potsherds to baby names and musical preferences. While this wide range of applications provides an opportunity for the development of generalisable analytical workflows, archaeological data present new questions and challenges that require further methodological and theoretical discussion. Here we examine the decorative motifs of Neolithic pottery from an archaeological assemblage in Western Germany, and argue that the widely used (and relatively undiscussed) assumption that observed frequencies are the result of a system in equilibrium conditions is unwarranted, and can lead to incorrect conclusions. We analyse our data with a simulation-based inferential framework that can overcome some of the intrinsic limitations in archaeological data, as well as handle both equilibrium conditions and instances where the mode of cultural transmission is time-variant. Results suggest that none of the models examined can produce the observed pattern under equilibrium conditions, and suggest. instead temporal shifts in the patterns of cultural transmission.

Inferring patterns of folktale diffusion using genomic data

Significance This paper presents unprecedented evidence on the transmission mechanism underlying the spread of a broad cross-cultural assemblage of folktales in Eurasia and Africa. State-of-the-art genomic evidence is used to directly assess the relevance of demic diffusion processes, in particular on the distribution of Old World folktales at intermediate geographic scales, and identify individual stories that are more likely to be transmitted through population movement and replacement. The results provide an empirical solution to operate with linguistic barriers and highlight the impossibility of disentangling genetic from geographic relationships at a cross-continental scale, warning against the direct use of extant genetic variability to infer processes of long-range cultural transmission. Observable patterns of cultural variation are consistently intertwined with demic movements, cultural diffusion, and adaptation to different ecological contexts [Cavalli-Sforza and Feldman (1981) Cultural Transmission and Evolution: A Quantitative Approach; Boyd and Richerson (1985) Culture and the Evolutionary Process]. The quantitative study of gene–culture coevolution has focused in particular on the mechanisms responsible for change in frequency and attributes of cultural traits, the spread of cultural information through demic and cultural diffusion, and detecting relationships between genetic and cultural lineages. Here, we make use of worldwide whole-genome sequences [Pagani et al. (2016) Nature 538:238–242] to assess the impact of processes involving population movement and replacement on cultural diversity, focusing on the variability observed in folktale traditions (n = 596) [Uther (2004) The Types of International Folktales: A Classification and Bibliography. Based on the System of Antti Aarne and Stith Thompson] in Eurasia. We find that a model of cultural diffusion predicted by isolation-by-distance alone is not sufficient to explain the observed patterns, especially at small spatial scales (up to ∼4,000 km). We also provide an empirical approach to infer presence and impact of ethnolinguistic barriers preventing the unbiased transmission of both genetic and cultural information. After correcting for the effect of ethnolinguistic boundaries, we show that, of the alternative models that we propose, the one entailing cultural diffusion biased by linguistic differences is the most plausible. Additionally, we identify 15 tales that are more likely to be predominantly transmitted through population movement and replacement and locate putative focal areas for a set of tales that are spread worldwide.

A matter of ephemerality: the study of Kel Tadrart Tuareg (southwest Libya) campsites via quantitative spatial analysis

Data used in this study were collected by one of the authors (SB) under the logistical and financial support of the Italian Archaeological Mission in the Sahara.

Modeling Demic and Cultural Diffusion: An Introduction

abstract Identifying the processes by which human cultures spread across different populations is one of the most topical objectives shared among different fields of study. Seminal works have analyzed 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 articles 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 modeling of these processes, briefly discuss the pros and cons of two of the most commonly used frameworks (equation-based models and agent-based models), and summarize the significance of each article in this special issue.

Modelling Settlement Rank-Size Fluctuations

This chapter proposes a model of long-term changes in human settlement pattern to identify possible generative processes behind empirically observed fluctuations in their rank-size pattern. The model assumes that per-capita fitness is a combination of the beneficial effect derived from the presence of other individuals in the same group and the finite amount of resource available locally. The former can lead to a positive frequency dependence, whereby an increase in the group size determines an increase in fitness; the latter can have detrimental effects once a group exceeds a certain size and the energetic demand becomes larger than what is available. Given that: (1) individuals have the possibility to modify their condition through group fission and fusion; and (2) the amount of resource is unlikely to be constant over space and time; we can expect fluctuations in the settlement pattern as a function of a non-linear relationship between size and fitness, as well as internally or externally induced variations in the amount of available resources. The simulation model will examine these scenarios and identify how different variables can induce different types of long-term equilibria in settlement systems.

Cultural Incubators and Spread of Innovation

abstract 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 form 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.