Denmark

Here we use the tools of behavioural ecology to try and understand the evolution of religious beliefs and practices; specifically our recent studies of the causes and consequences of religious celibacy in Amdo Tibetans (in western PRC). Historically a large number of young boys were sent to live a celibate life in monasteries. We find that this apparently costly practice of sending sons to the monastery, does in fact have kin selected benefits for other family members. We also examine the implication for local sex ratios, and for the workloads of men and women. It appears that ecology and kin selection can underpin apparently costly behaviours, generating gender biased behaviour and even the emergence of religious institutions.

Cultural Evolution Society 2022

Why be a monk? The evolutionary ecology of religious celibacy

keynote

### Welcome to the fourth Cultural Evolution Society Conference, CES2022! 

As last year, Underline will support the online component of the conference. The ongoing COVID-19 pandemic is causing a great deal of uncertainty for all of us. Therefore, we seek to offer a hybrid format that will hopefully allow some folks to travel to Aarhus, others to meet up locally or regionally in CES hub-lets, and other yet to participate online. The field of cultural evolution is growing in size and scope; its theories, methods and applications - both academic and applied - are getting ever more robust. Do join us in what promises to be an exciting exchange of ideas and a celebration of our field.

##### ***For SoMe interaction and live tweeting please tag @CulturalEvolSoc and use #CESconf2022***


#### The CES 2022 local organising committee
* Luseadra Joy McKerracher
* Jesper Sørensen 
* Niels Nørkjær Johannsen 
* Benjamin Grant Purzycki 
* Mette Løvschal 
* Felix Riede
* Iza Romanowska 
* Karsten Olsen

Please click on the button bellow if you want to watch the videos

The field of cultural evolution is growing in size and scope; its theories, methods and applications - both academic and applied - are getting ever more robust. Do join us in what promises to be an exciting exchange of ideas and a celebration of our field.

**Author(s):** Ben-Oren, Y; Kolodny, O; Creanza, N The transition to specialization of knowledge within populations could have facilitated the accumulation of cultural complexity in humans. Specialization allows populations to increase their cultural repertoire without requiring that members of that population increase their individual capacity to accumulate knowledge. However, specialization also means that domain-specific knowledge can be concentrated in small subsets of the population, making it more susceptible to loss. Here we use a model of cultural evolution to demonstrate that specialized populations can be more sensitive to stochastic loss of knowledge than populations without subdivision of knowledge, and that demographic and environmental changes have an amplified effect on populations with knowledge specialization. Finally, we suggest that specialization can be a double-edged sword; specialized populations may have an advantage in accumulating cultural traits but may also be less likely to expand and establish themselves successfully in new demes due to the increased cultural loss that they experience during the population bottlenecks that often characterize such expansions.

Cultural specialization as a double-edged sword: division into specialized guilds might promote cultural complexity at the cost of higher susceptibility to cultural loss

**Author(s):** Itao K; Kaneko K Anthropologists have observed gift relationships that establish social relations as well as the transference of goods in many human societies. The totality of social relations constitutes the network. Social scientists have analyzed different types of social organizations with characteristic network. However, the factors and mechanisms that cause the transition between these types are hardly explained. Here, we focus on the gift as the driving force for such change. We build the model by idealizing gift interactions and simulate the consequent social change due to long-term massive interactions. Through simulation, we demonstrate that as the frequency of the gift increases, the network structures are less clustered and more hierarchically organized. Also, the economic and social disparities successively emerge. These transition corresponds to the change from bands to tribes and to chiefdoms. Following this, statistical analysis using the Standard Cross-Cultural Sample, a global ethnographic database, empirically verifies the theoretical results on the emergence of disparities and hierarchical organizations due to the increase in the gift.

Transition of Social Organizations Driven by Gift Relationship

 When precise imitation of an average cultural trait (e.g. from multiple prestigious individuals) is the goal, the error-prone approximation of the average is the unavoidable outcome. The Galton-Pearson (GP) inheritance model, where a constant standard deviation characterises the error, is currently the mainstream in cultural evolution. We aimed to test whether this assumption is justified when individuals directly observe and imitate multiple 'phenotypes'. Each of 200 participants received 10 sheets of paper containing a randomly positioned pair of black dots and was instructed to mark an intermediate point between the dots as precisely as possible. Imitation error was directly proportional to the difference between demonstrator positions. The model, where the standard deviation of 'cultural offspring' is proportional to the standard deviation of 'cultural parents', explained 88% more variance than the GP model. Previous simulation work has shown that different inheritance models lead to different macroevolutionary patterns. Therefore, this result has profound implications for evolutionary trajectories if the adaptation is due to cultural and not biological inheritance.

Making a point: The imitation error is proportional to the difference between the demonstrators

**Author(s):** Barrett, BJ, Wild, S., Martin JM, Aplin LM Adoption of novel food is a major challenge for animals living in urban environments; the spread of innovation and establishment of traditions is one potential mechanism enabling its incorporation. Experimental introductions into groups of the same population have been a classic method to examine this mechanistic pathway. However, most studies have focused on the social learning of foraging techniques, which may have different associated social or cognitive biases. In this study, we conducted a two option and control experiment, presenting two novel foods (shelled almonds, coloured red or blue) in five neighbouring roosts of sulphur-crested cockatoos (Cacatua galerita). We tracked the spread of knowledge across social networks from trained demonstrators, and used experience weighted attraction models (EWA) to ask: (i) how social learning biases shape the acquisition of a novel food, and (ii) whether similarities in processing techniques can emerge within roosts or social associates, even in a continuous population. Examining the solves of 355 individuals, we found age-related differences, with juveniles - but not adults - exhibiting a conformist bias, preferentially choosing the most frequently eaten food. Lastly, when analysing 539 openings by 147 individuals, we found evidence for site-level differences that increased with distance and decreased with movement between sites.

Cultural diffusion experiments with novel food reveal age-dependent conformity and potential foraging traditions in neighbouring groups of urban parrots

**Author(s):** Nilo M. Recalde, Ben C. Sheldon Population processes like dispersal, immigration and turnover play an essential role in evolution: they determine which individuals meet and reproduce and, as a result, shape the distribution of genetic diversity over space and time. By influencing when and which individuals interact, these processes also have the potential to affect traits that are culturally, rather than genetically, inherited, such as bird song. 


Teasing apart the relative contributions of population processes to the evolution of cultural traits is difficult, however, because it requires dense trait sampling and detailed individual life-history data—both notoriously hard to acquire in wild populations. To this end, we have built a multi-generational dataset containing the full song repertoires of hundreds of individuals in a population of great tits (Parus major) monitored extensively at Wytham Woods, UK. 


While simple at first impression, great tit songs are surprisingly diverse, and they give rise to a population-level cultural landscape that shifts continuously. Here, we take advantage of our long-term individual data and, using newly developed computational tools for studying large bird song datasets, show how demographic factors contribute to shaping local song diversity and complexity over multiple spatial and temporal scales.

Demography and cultural evolution in the wild: the landscape of diversity in bird song

**Author(s):** Colleran, Heidi Introduction: The demographic transition still remains a mystery. A shift from vertical to horizontal transmission is deemed instrumental in the spread of low fertility values, but we lack a mechanistic explanation for such a shift. Women’s personal advice networks are where ideas about fertility practices are exchanged, and are key to understanding this change. We expect that economic and cultural changes in rural areas lead to increasingly valuing non-kin over kin, and ego characteristics influence these friendship dynamics. 
Methods:
Here, using comprehensive demographic and relational data from 22 communities in rural Poland, we investigated how women’s personal networks change with ego-level attributes, and how network characteristics affect cultural transmission. We focused on network composition and interaction, bi-lateral social support, closeness and emotional support. 
Results:
We found that women characterized by less traditional values (i.e. high education, non-farming occupation) have less kin and more unrelated friends in their networks, who they rely on for emotional support. Women characterized by traditional rural values rely on genetic kin and affines, for practical and financial support. Importantly, we found trade-offs between types of support across women. 
Conclusions: These shifting networks moderate information transmission and help explain the cultural transmission of low fertility values.

Female friendship and the horizontal transmission of low fertility values

**Author(s):** Lu, Y. T.; Colleran, H. Fertility decline may involve quantity-quality trade-offs among children, and many studies assume this is adaptive via costs and benefits of wealth accumulation and transmission. Few models have explored these hypotheses over the long term. Here we ask: does wealth-stratification generate fertility declines when the marginal costs to reproduction (interpretable as cultural or economic perceptions) differ by class? 

We develop an ABM whereby agents inherit both parental wealth and a resource allocation strategy. They allocate wealth between fertility and inheritance in 1) a setting with density-dependent death and 2) a setting where wealth classes experience differential costs to reproduction. Descendant wealth is determined by the combination of inheritance and a random income contribution from the environment.

Preliminary results show that parents investing more in fertility than bequests leave more descendants over time. This dynamic converges faster in the second setting. Greater stratification also leads upper-class parents to have fewer children than the middle class, consistent with arguments that the wealthiest classes lead the demographic transitions.

We suggest that wealth stratification may be crucial in explaining historical fertility.

The coevolution of human fertility and wealth stratification

A preference for having a particular number of children is a cultural trait expected to influence the fertility outcome of a woman. However, fertility preferences often do not match with the realised fertility of a woman. This pattern is probably because not much is known on how fertility desires actually vary, only that they are highly context-dependant. Furthermore, there is no clear understanding on how the social context shapes the fertility preferences of a woman. Here, we study how the social fertility context at the family, peer, and community level shapes the ideal family size of women from rural Poland. 
We build a Bayesian cross-classified multi-level model to account for the structure in the clustering at the family, peer, and community levels, and analyse how the average number of children ever born among clusters may shape the ideal number of children of Polish women (n=1,995). 
The results will show to what extent the ideal number of children is clustered at the family, peer, and community levels. Specifically, the results will show how the mean fertility of the different clusters predicts the direction of the fertility preferences of a woman. 
Knowing how the variability of fertility preferences is decomposed among the family, peers, and community levels can contribute to understand how the social context shapes culturally transmitted traits related to fertility.

How family, peers, and community matter in the differences of fertility preferences among women from rural Poland

 One of the central challenges facing the designers of cultural database projects is that of ontology. What should the units of analysis be? Should multiple units be allowed and, if so, how should they be related? In this talk we will explain how the Database of Religious History (DRH) project has responded to this challenge, explore the advantages and disadvantages of the approach we have adopted, and describe the tension we have confronted between allowing units of analysis to proliferate and maintaining coherence and usability in the database.

The Question of Ontology in Cultural Database Projects

 The Database of Religious History (DRH) consists of a series of polls, including mainly quantitative questions. There are many challenges for the analysis of DRH data—How to select a sample of religious groups? How to handle missing data? How to handle disagreement between experts? In this presentation I will address how these challenges have been managed in recent analysis. In particular I will focus on the challenge of defining a useful data set from the DRH sample to answer specific questions.

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Why be a monk? The evolutionary ecology of religious celibacy

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Cultural specialization as a double-edged sword: division into specialized guilds might promote cultural complexity at the cost of higher susceptibility to cultural loss

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