scholarly journals Collective narratives catalyse cooperation

2020 ◽  
Author(s):  
Chaitanya Gokhale ◽  
Joseph Bulbulia ◽  
Marcus Frean
Keyword(s):  
Fundamental Problem ◽  
Evolutionary Model ◽  
Human Sciences ◽  
Finite Populations ◽  
Hunter Gatherers ◽  
Moral Exemplars ◽  
Cultural Selection ◽  
Evolutionary Theories ◽  
Collective Narratives ◽  
Population Sizes

Humans invest in fantastic stories -- mythologies.Recent evolutionary theories suggest that cultural selection may favour moralising stories that motivate prosocial behaviours.A key challenge is to explain the emergence of mythologies that lack explicit moral exemplars or directives. Here, we resolve this puzzle with an evolutionary model in which arbitrary mythologies transform a collection of egoistic individuals into a cooperative. Importantly, in finite populations, reflecting relative to contemporary population sizes of hunter-gatherers, the model is robust to the cognitive costs in adopting fictions. This approach resolves a fundamental problem across the human sciences by explaining the evolution of otherwise puzzling amoral, nonsensical, and fictional narratives as exquisitely functional coordination devices.

scholarly journals Recombination Can Evolve in Large Finite Populations Given Selection on Sufficient Loci

Genetics ◽  
2003 ◽  
Vol 165 (4) ◽  
pp. 2249-2258 ◽  
Author(s):  
Mark M Iles ◽  
Kevin Walters ◽  
Chris Cannings
Keyword(s):  
Experimental Evidence ◽  
Genetic Drift ◽  
Finite Population ◽  
Selective Advantage ◽  
Indirect Selection ◽  
Small Populations ◽  
Finite Populations ◽  
Population Sizes ◽  
Population Recombination

AbstractIt is well known that an allele causing increased recombination is expected to proliferate as a result of genetic drift in a finite population undergoing selection, without requiring other mechanisms. This is supported by recent simulations apparently demonstrating that, in small populations, drift is more important than epistasis in increasing recombination, with this effect disappearing in larger finite populations. However, recent experimental evidence finds a greater advantage for recombination in larger populations. These results are reconciled by demonstrating through simulation without epistasis that for m loci recombination has an appreciable selective advantage over a range of population sizes (am, bm). bm increases steadily with m while am remains fairly static. Thus, however large the finite population, if selection acts on sufficiently many loci, an allele that increases recombination is selected for. We show that as selection acts on our finite population, recombination increases the variance in expected log fitness, causing indirect selection on a recombination-modifying locus. This effect is enhanced in those populations with more loci because the variance in phenotypic fitnesses in relation to the possible range will be smaller. Thus fixation of a particular haplotype is less likely to occur, increasing the advantage of recombination.

scholarly journals Polygenic local adaptation in metapopulations: a stochastic eco-evolutionary model

2020 ◽  
Author(s):  
Enikő Szép ◽  
Himani Sachdeva ◽  
Nick Barton
Keyword(s):  
Population Size ◽  
Local Adaptation ◽  
Genetic Drift ◽  
Diffusion Approximation ◽  
Joint Distribution ◽  
Evolutionary Model ◽  
Ecological Niches ◽  
Demographic Stochasticity ◽  
Linkage Disequilibria ◽  
Population Sizes

AbstractThis paper analyses the conditions for local adaptation in a metapopulation with infinitely many islands under a model of hard selection, where population size depends on local fitness. Each island belongs to one of two distinct ecological niches or habitats. Fitness is influenced by an additive trait which is under habitat-dependent directional selection. Our analysis is based on the diffusion approximation and accounts for both genetic drift and demographic stochasticity. By neglecting linkage disequilibria, it yields the joint distribution of allele frequencies and population size on each island. We find that under hard selection, the conditions for local adaptation in a rare habitat are more restrictive for more polygenic traits: even moderate migration load per locus at very many loci is sufficient for population sizes to decline. This further reduces the efficacy of selection at individual loci due to increased drift and because smaller populations are more prone to swamping due to migration, causing a positive feedback between increasing maladaptation and declining population sizes. Our analysis also highlights the importance of demographic stochasticity, which exacerbates the decline in numbers of maladapted populations, leading to population collapse in the rare habitat at significantly lower migration than predicted by deterministic arguments.

scholarly journals Tracking Hunter-Gatherer Impact on Vegetation in Last Interglacial and Holocene Europe: Proxies and Challenges

2022 ◽  
Author(s):  
Anastasia Nikulina ◽  
Katharine MacDonald ◽  
Fulco Scherjon ◽  
Elena A. Pearce ◽  
Marco Davoli ◽  
...  
Keyword(s):  
Niche Construction ◽  
Local Level ◽  
Last Interglacial ◽  
Hunter Gatherers ◽  
Clear Cut ◽  
Ethnographic Studies ◽  
Published Evidence ◽  
Time Period ◽  
Modelling Studies ◽  
Population Sizes

AbstractWe review palaeoenvironmental proxies and combinations of these relevant for understanding hunter-gatherer niche construction activities in pre-agricultural Europe. Our approach consists of two steps: (1) identify the possible range of hunter-gatherer impacts on landscapes based on ethnographic studies; (2) evaluate proxies possibly reflecting these impacts for both the Eemian (Last Interglacial, Middle Palaeolithic) and the Early–Middle Holocene (Mesolithic). We found these paleoenvironmental proxies were not able to unequivocally establish clear-cut differences between specific anthropogenic, climatic and megafaunal impacts for either time period in this area. We discuss case studies for both periods and show that published evidence for Mesolithic manipulation of landscapes is based on the interpretation of comparable data as available for the Last Interglacial. If one applies the ‘Mesolithic’ interpretation schemes to the Neanderthal record, three common niche construction activities can be hypothesised: vegetation burning, plant manipulation and impact on animal species presence and abundance. Our review suggests that as strong a case can be made for a Neanderthal impact on landscapes as for anthropogenic landscape changes during the Mesolithic, even though the Neanderthal evidence comes from only one high-resolution site complex. Further research should include attempts (e.g. by means of modelling studies) to establish whether hunter-gatherer impact on landscapes played out at a local level only versus at a larger scale during both time periods, while we also need to obtain comparative data on the population sizes of Last Interglacial and Holocene hunter-gatherers, as these are usually inferred to have differed significantly.

scholarly journals Escalation of Memory Length in Finite Populations

2017 ◽  
Author(s):  
Kyle Harrington ◽  
Jordan Pollack
Keyword(s):  
Computational Simulations ◽  
Finite Populations ◽  
Arms Races ◽  
Memory Length ◽  
Satisfactory Degree ◽  
Cooperative Strategies ◽  
Population Sizes ◽  
Strategic Complexity ◽  
Counter Argument

AbstractThe escalation of complexity is a commonly cited benefit of coevolutionary systems, but computational simulations generally fail to demonstrate this capacity to a satisfactory degree. We draw on a macroevolutionary theory of escalation to develop a set of criteria for coevolutionary systems to exhibit escalation of strategic complexity. By expanding on a previously developed model of the evolution of memory length for cooperative strategies by Kristian Lindgren, we resolve previously observed limitations to the escalation of memory length. We present long-term coevolutionary simulations showing that larger population sizes tend to support greater escalation of complexity than smaller population sizes. Additionally, escalation is sensitive to perturbation during transitions of complexity. In whole, a long-standing counter-argument to the ubiquitous nature of coevolution is resolved, suggesting that the escalation of coevolutionary arms races can be harnessed by computational simulations.

scholarly journals Whole genomes reveal severe bottleneck among Asian hunter-gatherers following the invention of agriculture

2020 ◽  
Author(s):  
Saikat Chakraborty ◽  
Analabha Basu ◽  
Keyword(s):  
Population Size ◽  
South Asian ◽  
Fold Increase ◽  
High Coverage ◽  
Hunter Gatherers ◽  
Differential Fertility ◽  
Whole Genomes ◽  
Anatomically Modern Humans ◽  
Population Sizes ◽  
Global Population

AbstractThe invention of agriculture (IOA) by anatomically modern humans (AMH) around 10,000 years before present (ybp) is known to have led to an increase in AMH’s carrying capacity and hence its population size. Reconstruction of historical demography using high coverage (~30X) whole genome sequences (WGS) from >700 individuals from different South Asian (SAS) and Southeast Asian (SEA) populations reveals that although several present day populous groups did indeed experience a positive Neolithic Demographic Transition (NDT), most hunter-gatherers (HGs) experienced a demographic decrease. Differential fertility between HGs and non-HGs, exposure of HGs to novel pathogens from non-HGs could have resulted in such contrasting patterns. However, we think the most parsimonious explanation of the drastic decrease in population size of HGs is their displacement/enslavement by non-HGs.Significance StatementThe invention of agriculture, around 10000 years ago, facilitated more food production which could feed larger populations. This had far-reaching socio-political and demographic impacts, including a ~10,000 fold increase in global population-size in the last 10,000 years. However, this increase in population size is not a universal truth and present day hunter-gatherer populations, in contrast, have dwindled in size, often drastically. The signatures of this rise in population size are discernible from the genomes of present-day individuals. Using genomic data, we show that for the majority of Asian hunter-gatherers, population-sizes drastically decreased following the invention of agriculture. We argue that a combination of displacement, enslavement and disease resulted in the decimation of hunter-gatherer societies.

scholarly journals Compliance and confirmation bias on the emergence of cultural conventions

2021 ◽  
Author(s):  
José Segovia-Martín
Keyword(s):  
Learning Algorithm ◽  
Initial Conditions ◽  
Confirmation Bias ◽  
Evolutionary Model ◽  
Alpha Diversity ◽  
Value Systems ◽  
Institutional Values ◽  
Institutional Influence ◽  
Population Sizes ◽  
Different Levels

In the present study we develop a co-evolutionary model of cardinal preferences and institutions to explore how the dynamics of cultural diversity in populations with different levels of compliance and confirmation bias evolve. This is the first attempt to formalise these two types of bias in a single learning algorithm for agents learning in iterative chains without access to completeinformation. Results show that, in some regions of the parameter space, institutional influence facilitates the emergence of shared cultural conventions when compliance biases increase. In general, a compliance bias pushes diversity up when institutions are diverse, and pushes diversity down when institutions convey value systems with strong dominance of one or few cultural variants. Interestingly, in some scenarios, a decrease in institutional influence and compliance bias allows theemergence of cultural conventions from the mutual reinforcement of local interactions and institutional values. We asses the robustness of these results by examining how sensitively they depend on different initial conditions of variant assignment, population sizes and alpha diversity indexes.

scholarly journals Evolution of mating types in finite populations: the precarious advantage of being rare

2018 ◽  
Author(s):  
Peter Czuppon ◽  
David W. Rogers
Keyword(s):  
Mating Types ◽  
Relative Importance ◽  
Self Incompatibility ◽  
Finite Populations ◽  
Random Drift ◽  
Explicit Formulas ◽  
Rare Type ◽  
Increased Risk ◽  
Population Sizes ◽  
The Cost

AbstractSexually reproducing populations with self-incompatibility bear the cost of limiting potential mates to individuals of a different type. Rare mating types escape this cost since they are unlikely to encounter incompatible partners, leading to the deterministic prediction of continuous invasion by new mutants and an ever increasing number of types. However, rare types are also at an increased risk of being lost by random drift. Calculating the number of mating types that a population can maintain requires consideration of both the deterministic advantages and the stochastic risks. By comparing the relative importance of selection and drift, we show that a population of size N can maintain a maximum of approximately N1/3 mating types for intermediate population sizes while for large N we derive a formal estimate. Although the number of mating types in a population is quite stable, the rare type advantage promotes turnover of types. We derive explicit formulas for both the invasion and turnover probabilities in finite populations.

scholarly journals Ecological opportunity and predator–prey interactions: linking eco-evolutionary processes and diversification in adaptive radiations

2018 ◽  
Vol 285 (1874) ◽  
pp. 20172550 ◽  
Author(s):  
Mikael Pontarp ◽  
Owen L. Petchey
Keyword(s):  
Evolutionary Model ◽  
Relative Strength ◽  
Disruptive Selection ◽  
Ecological Opportunity ◽  
Predator Prey ◽  
Negative Effect ◽  
Population Sizes ◽  
Adaptive Radiations ◽  
Early Phases ◽  
Insight Into

Much of life's diversity has arisen through ecological opportunity and adaptive radiations, but the mechanistic underpinning of such diversification is not fully understood. Competition and predation can affect adaptive radiations, but contrasting theoretical and empirical results show that they can both promote and interrupt diversification. A mechanistic understanding of the link between microevolutionary processes and macroevolutionary patterns is thus needed, especially in trophic communities. Here, we use a trait-based eco-evolutionary model to investigate the mechanisms linking competition, predation and adaptive radiations. By combining available micro-evolutionary theory and simulations of adaptive radiations we show that intraspecific competition is crucial for diversification as it induces disruptive selection, in particular in early phases of radiation. The diversification rate is however decreased in later phases owing to interspecific competition as niche availability, and population sizes are decreased. We provide new insight into how predation tends to have a negative effect on prey diversification through decreased population sizes, decreased disruptive selection and through the exclusion of prey from parts of niche space. The seemingly disparate effects of competition and predation on adaptive radiations, listed in the literature, may thus be acting and interacting in the same adaptive radiation at different relative strength as the radiation progresses.

scholarly journals Biophysics and population size constrains speciation in an evolutionary model of developmental system drift

2017 ◽  
Author(s):  
Bhavin S. Khatri ◽  
Richard A. Goldstein
Keyword(s):  
Population Size ◽  
Large Population ◽  
Evolutionary Model ◽  
Closely Related Species ◽  
Developmental System ◽  
Diffusive Growth ◽  
Developmental System Drift ◽  
Population Sizes ◽  
Mechanistic Basis ◽  
Molecular Phenotypes

Developmental system drift is a likely mechanism for the origin of hybrid incompatibilities between closely related species. We examine here the detailed mechanistic basis of hybrid incompatibilities for a genotype-phenotype map for developmental system drift under stabilising selection, where the organismal phenotype is conserved, but the underlying molecular phenotypes and genotype can drift. This leads to number of emergent phenomenon not obtainable by modelling genotype or phenotype alone. Our results show that: 1) speciation is more rapid at smaller population sizes with a characteristic, Orr-like, power law, but at large population sizes slow, characterised by a sub-diffusive growth law; 2) the molecular phenotypes under weakest selection contribute to the earliest incompatibilities; and 3) pairwise incompatibilities dominate over higher order, contrary to previous predictions that the latter should dominate. Our results indicate that biophysics and population size provide a much stronger constraint to speciation than suggested by previous models.

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