publications

2023

1. Child Dev Persp

   Peer Learning and Cultural Evolution

   Sheina Lew-Levy, Wouter van den Bos, Kathleen Corriveau, Natália Dutra, Emma Flynn, Eoin O’Sullivan, Sarah Pope-Caldwell, Bruce Rawlings, Marco Smolla, Jing Xu, and Lara Wood

   Child Development Perspectives, 2023

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   In this article, we integrate cultural evolutionary theory with empirical research from developmental psychology, cultural anthropology, and primatology to explore the role of peer learning in the development of complex instrumental skills and behavioral norms. We show that instrumental imitation, contingent teaching, generative collaboration, and selective copying contribute to domain-specific transmission of knowledge between peers. Stages of development and characteristics inherent to the learner and model influence how and when children learn from each other. Peer learning is persistent across societies despite cultural beliefs that favor adult–child transmission in some settings. Comparative research hints at the possibility that children’s greater motivation to interact with and learn from each other may set humans apart from other primates. We conclude by outlining avenues for future research, including how individual characteristics and developmental changes in social networks, motivation, and cognition may contribute to cultural evolution.

2. Evol Hum Sci

   Pathways to cultural adaptation: the coevolution of cumulative culture and social networks

   Marco Smolla, and Erol Akçay

   2023

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   Humans have adapted to an immense array of environments by accumulating culturally transmitted knowledge and skills. Adaptive culture can accumulate either via more distinct cultural traits or via improvements of existing cultural traits. The kind of culture that accumulates depends on, and coevolves with, the social structure of societies. Here, we show that the coevolution of learning networks and cumulative culture results in two distinct pathways to cultural adaptation: highly connected populations with high proficiency but low trait diversity vs. sparsely connected populations with low proficiency but higher trait diversity. Importantly, we show there is a conflict between group-level payoffs, which are maximised in highly connected groups that attain high proficiency, and individual level selection, which favours disconnection. This conflict emerges from the interaction of social learning with population structure and causes populations to cycle between the two cultural and network states. The same conflict creates a paradox where increasing innovation rate lowers group payoffs. Finally, we explore how populations navigate these two pathways in environments where payoffs differ among traits and can change over time, showing that high proficiency is favoured when payoffs are stable and vary strongly between traits, while frequent changes in trait payoffs favour more trait diversity. Our results illustrate the complex interplay between networks, learning and the environment, and so inform our understanding of human social evolution.

2022

1. Routledge

   Individual-Based Models of Cultural Evolution: A Step-by-Step Guide Using R

   Alberto Acerbi, Alex Mesoudi, and Marco Smolla

   2022

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   "Individual-Based Models of Cultural Evolution shows readers how to create individual-based models of cultural evolution using the programming language R. The field of cultural evolution has emerged in the last few decades as a thriving, interdisciplinary effort to understand cultural change and cultural diversity within an evolutionary framework and using evolutionary tools, concepts and methods"–

2. SocArXiv

   Reciprocity Supports Cooperation in Real-World Economic Interactions

   Taylor Z. Lange, Marco Smolla, and Timothy Waring

   May 2022

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   Evolutionary scientists argue that cooperation is central to human ecological success. Theoretical models, and behavioral experiments have found that human cooperation is conditional and context dependent, that individuals vary in their propensity to cooperate, and that cooperation can be stabilized by reciprocity within a group. However, outside of behavioral experiments, these findings have been difficult to validate with observations of cooperation in natural settings, especially in industrial societies, cash economies and structured organizational contexts. Here, we report in situ observations of behavioral cooperation and reciprocity from organizations embedded in a cash economy. We study small consumer food cooperatives or ‘food clubs’, in which members share bulk food purchases, and are considered to be heavily dependent on cooperation. We take advantage of a high-resolution purchasing dataset of all economic interactions for 1,528 individuals across 35 clubs, including 10,261 bulk purchases over a combined total of 107 years of club purchasing data. We develop a network method to detect economic reciprocity, categorize economic behavior as directly reciprocal, indirectly reciprocal, or non-reciprocal, and statistically classify individual behavioral types (reciprocator, helper, and beneficiary). Observed patterns of reciprocity confirm the central findings of theoretical and experimental studies. Reciprocity is highly abundant in most clubs, with direct reciprocity far more common (72%) than indirect reciprocity (11%). Reciprocators are the most common (69%) and the most stable behavioral type, but clubs vary significantly. Our results provide some of the first observational evidence of economic reciprocity and cooperation generally. They imply that cooperation may be a more important force in industrial societies, organizational contexts, and cash economies than currently understood. These results solidify the findings of the behavioral study of cooperation and open the door for greater study and application of cooperation in organizational management and economic policy.

3. An Rev Anth

   What Makes Inventions Become Traditions?

   Susan E. Perry, Alecia Carter, Jacob G. Foster, Sabine Nöbel, and Marco Smolla

   Annual Review of Anthropology, Oct 2022

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   Although anthropology was the first academic discipline to investigate cultural change, many other disciplines have made noteworthy contributions to understanding what influences the adoption of new behaviors. Drawing on a broad, interdisciplinary literature covering both humans and nonhumans, we examine ( a) which features of behavioral traits make them more transmissible, ( b) which individual characteristics of inventors promote copying of their inventions, ( c) which characteristics of individuals make them more prone to adopting new behaviors, ( d) which characteristics of dyadic relationships promote cultural transmission, ( e) which properties of groups (e.g., network structures) promote transmission of traits, and ( f) which characteristics of groups promote retention, rather than extinction, of cultural traits. One of anthropology’s strengths is its readiness to adopt and improve theories and methods from other disciplines, integrating them into a more holistic approach; hence, we identify approaches that might be particularly useful to biological and cultural anthropologists, and knowledge gaps that should be filled.

2021

1. Phil Trans B

   Not by Transmission Alone: The Role of Invention in Cultural Evolution

   Susan Perry, Alecia Carter, Marco Smolla, Erol Akçay, Sabine Nöbel, Jacob G. Foster, and Susan D. Healy

   Philosophical Transactions of the Royal Society B: Biological Sciences, Jul 2021

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   Innovation—the combination of invention and social learning—can empower species to invade new niches via cultural adaptation. Social learning has typically been regarded as the fundamental driver for the emergence of traditions and thus culture. Consequently, invention has been relatively understudied outside the human lineage—despite being the source of new traditions. This neglect leaves basic questions unanswered: what factors promote the creation of new ideas and practices? What affects their spread or loss? We critically review the existing literature, focusing on four levels of investigation: traits (what sorts of behaviours are easiest to invent?), individuals (what factors make some individuals more likely to be inventors?), ecological contexts (what aspects of the environment make invention or transmission more likely?), and populations (what features of relationships and societies promote the rise and spread of new inventions?). We aim to inspire new research by highlighting theoretical and empirical gaps in the study of innovation, focusing primarily on inventions in non-humans. Understanding the role of invention and innovation in the history of life requires a well-developed theoretical framework (which embraces cognitive processes) and a taxonomically broad, cross-species dataset that explicitly investigates inventions and their transmission. We outline such an agenda here. This article is part of the theme issue ‘Foundations of cultural evolution’.

2. Phil Trans B

   Underappreciated Features of Cultural Evolution

   Marco Smolla, Fredrik Jansson, Laurent Lehmann, Wybo Houkes, Franz J. Weissing, Peter Hammerstein, Sasha R. X. Dall, Bram Kuijper, and Magnus Enquist

   Philosophical Transactions of the Royal Society B: Biological Sciences, Jul 2021

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   Cultural evolution theory has long been inspired by evolutionary biology. Conceptual analogies between biological and cultural evolution have led to the adoption of a range of formal theoretical approaches from population dynamics and genetics. However, this has resulted in a research programme with a strong focus on cultural transmission. Here, we contrast biological with cultural evolution, and highlight aspects of cultural evolution that have not received sufficient attention previously. We outline possible implications for evolutionary dynamics and argue that not taking them into account will limit our understanding of cultural systems. We propose 12 key questions for future research, among which are calls to improve our understanding of the combinatorial properties of cultural innovation, and the role of development and life history in cultural dynamics. Finally, we discuss how this vibrant research field can make progress by embracing its multidisciplinary nature. This article is part of the theme issue ‘Foundations of cultural evolution’.

2020

1. Proc B

   Competition for Resources Can Promote the Divergence of Social Learning Phenotypes

   R. Tucker Gilman, Fern Johnson, and Marco Smolla

   Proceedings of the Royal Society B: Biological Sciences, Feb 2020

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   Social learning occurs when animals acquire knowledge or skills by observing or interacting with others and is the fundamental building block of culture. Within populations, some individuals use social learning more frequently than others, but why social learning phenotypes differ among individuals is poorly understood. We modelled the evolution of social learning frequency in a system where foragers compete for resources, and there are many different foraging options to learn about. Social learning phenotypes diverged when some options offered much better rewards than others and expected rewards changed moderately quickly over time. When options offered similar rewards or when rewards changed slowly, a single social learning phenotype evolved. This held for fixed and simple conditional social learning rules. Sufficiently complex conditional social learning rules prevented the divergence of social learning phenotypes under all conditions. Our results explain how competition can promote the divergence of social learning phenotypes.

2. Proc B

   Evolution of Contribution Timing in Public Goods Games

   Bryce Morsky, Marco Smolla, and Erol Akçay

   Proceedings of the Royal Society B: Biological Sciences, May 2020

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   Life-history strategies are a crucial aspect of life, which are complicated in group-living species, where pay-offs additionally depend on others’ behaviours. Previous theoretical models of public goods games have generally focused on the amounts individuals contribute to the public good. Yet a much less-studied strategic aspect of public goods games, the timing of contributions, can also have dramatic consequences for individual and collective performance. Here, we develop two stage game theoretical models to explore how the timing of contributions evolves. In the first stage, individuals contribute to a threshold public good based on a performance schedule. The second stage begins once the threshold is met, and the individuals then compete as a function of their performance. We show how contributing rapidly is not necessarily optimal, because delayers can act as ‘cheats,’ avoiding contributing while reaping the benefits of the public good. However, delaying too long can put the delayers at a disadvantage as they may be ill-equipped to compete. These effects lead to bistability in a single group, and spatial diversity among multiple interacting groups.

3. Phil Trans B

   Capuchin Monkey Rituals: An Interdisciplinary Study of Form and Function

   Susan Perry, and Marco Smolla

   Philosophical Transactions of the Royal Society B: Biological Sciences, Aug 2020

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   Many white-faced capuchin monkey dyads in Lomas Barbudal, Costa Rica, practise idiosyncratic interaction sequences that are not part of the species-typical behavioural repertoire. These interactions often include uncomfortable or risky elements. These interactions exhibit the following characteristics commonly featured in definitions of rituals in humans: (i) they involve an unusual intensity of focus on the partner, (ii) the behaviours have no immediate utilitarian purpose, (iii) they sometimes involve ‘sacred objects’, (iv) the distribution of these behaviours suggests that they are invented and spread via social learning, and (v) many behaviours in these rituals are repurposed from other behavioural domains (e.g. extractive foraging). However, in contrast with some definitions of ritual, capuchin rituals are not overly rigid in their form, nor do the sequences have specific opening and closing actions. In our 9260 h of observation, ritual performance rate was uncorrelated with amount of time dyads spent in proximity but (modestly) associated with higher relationship quality and rate of coalition formation across dyads. Our results suggest that capuchin rituals serve a bond-testing rather than a bond-strengthening function. Ritual interactions are exclusively dyadic, and between-dyad consistency in form is low, casting doubt on the alternative hypothesis that they enhance group-wide solidarity. This article is part of the theme issue ‘Ritual renaissance: new insights into the most human of behaviours’.

2019

1. SciAdv

   Cultural Selection Shapes Network Structure

   Marco Smolla, and Erol Akçay

   Science Advances, Aug 2019

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   Cultural evolution relies on the social transmission of cultural traits along a population’s social network. Research indicates that network structure affects information spread and thus the capacity for cumulative culture. However, how network structure itself is driven by population-culture co-evolution remains largely unclear. We use a simple model to investigate how populations negotiate the trade-off between acquiring new skills and getting better at existing skills and how this trade-off shapes social networks. We find unexpected eco-evolutionary feedbacks from culture onto social networks and vice versa. We show that selecting for skill generalists results in sparse networks with diverse skill sets, whereas selecting for skill specialists results in dense networks and a population that specializes on the same few skills on which everyone is an expert. Our model advances our understanding of the complex feedbacks in cultural evolution and demonstrates how individual-level behavior can lead to the emergence of population-level structure.

2. R Soc Open Sci

   Reproductive Skew Affects Social Information Use

   Marco Smolla, Charlotte Rosher, R. Tucker Gilman, and Susanne Shultz

   Royal Society Open Science, Jul 2019

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   Individuals vary in their propensity to use social learning, the engine of cultural evolution, to acquire information about their environment. The causes of those differences, however, remain largely unclear. Using an agent-based model, we tested the hypothesis that as a result of reproductive skew differences in energetic requirements for reproduction affect the value of social information. We found that social learning is associated with lower variance in yield and is more likely to evolve in risk- averse low-skew populations than in high-skew populations. Reproductive skew may also result in sex differences in social information use, as empirical data suggest that females are often more risk-averse than males. To explore how risk may affect sex differences in learning strategies, we simulated learning in sexually reproducing populations where one sex experiences more reproductive skew than the other. When both sexes compete for the same resources, they tend to adopt extreme strategies: the sex with greater reproductive skew approaches pure individual learning and the other approaches pure social learning. These results provide insight into the conditions that promote individual and species level variation in social learning and so may affect cultural evolution.

2018

1. Evol Anthro

   Second Annual Workshop of the Association of Early-Career Social Learning Researchers in St Andrews, Scotland

   Marco Smolla, Edith Invernizzi, Marina Bazhydai, Marco Casoli, Dominik Deffner, Gonçalo S. Faria, Nicholas Jones, Jasmeen Kanwal, Anna-Margarete Staehler, and Ryutaro Uchiyama

   Evolutionary Anthropology: Issues, News, and Reviews, Jul 2018

2016

1. Meth Eco Evol

   Similarity in Spatial Utilization Distributions Measured by the Earth Mover’s Distance

   Bart Kranstauber, Marco Smolla, and Kamran Safi

   Methods in Ecology and Evolution, Jul 2016

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   Estimating the similarity in space use (spatio-temporal home range overlap) of animals is important formany questions regarding behavioural ecology, wildlife management and conservation. The current methods that calculate joint space use generally do not account for proximity in space use, as all of them rely on the differences between the exact spatial overlay of utilization distributions, while spatial distances between distributions should be considered to truly quantify similarity.

2. Phil Trans B

   Copy-When-Uncertain: Bumblebees Rely on Social Information When Rewards Are Highly Variable

   Marco Smolla, Sylvain Alem, Lars Chittka, and Susanne Shultz

   Biology Letters, Jul 2016

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   To understand the relative benefits of social and personal information use in foraging decisions, we developed an agent-based model of social learning that predicts social information should be more adaptive where resources are highly variable and personal information where resources vary little. We tested our predictions with bumblebees and found that foragers relied more on social information when resources were variable than when they were not. We then investigated whether socially salient cues are used prefer- entially over non-social ones in variable environments. Although bees clearly used social cues in highly variable environments, under the same conditions they did not use non-social cues. These results suggest that bumblebees use a ‘copy-when-uncertain’ strategy.

2015

1. Proc B

   Competition for Resources Can Explain Patterns of Social and Individual Learning in Nature

   Marco Smolla, R Tucker Gilman, Tobias Galla, and Susanne Shultz

   Proceedings of the Royal Society B: Biological Sciences, Jul 2015

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   In nature, animals often ignore socially available information despite the multiple theoretical benefits of social learning over individual trial-and-error learning. Using information filtered by others is quicker, more efficient and less risky than randomly sampling the environment. To explain the mix of social and individual learning used by animals in nature, most models penalize the quality of socially derived information as either out of date, of poor fidelity or costly to acquire. Competition for limited resources, a fundamental evolutionary force, provides a compelling, yet hitherto overlooked, explanation for the evolution of mixed-learning strategies. We present a novel model of social learning that incorporates competition and demonstrates that (i) social learning is favoured when competition is weak, but (ii) if competition is strong social learning is favoured only when resource quality is highly variable and there is low environmental turnover. The frequency of social learning in our model always evolves until it reduces the mean foraging success of the population. The results of our model are consistent with empirical studies showing that individuals rely less on social information where resources vary little in quality and where there is high within-patch competition. Our model provides a framework for understanding the evolution of social learning, a prerequisite for human cumulative culture.