Virulence decomposition for bifurcating infections.

A fundamental goal in infection biology is to understand the emergence of variation in pathogen virulence-here defined as the decrease in host fitness caused by a pathogen. To uncover the sources of such variation, virulence can be decomposed into both host- and pathogen-associated components. However, decomposing virulence can be challenging owing to complex within-host pathogen dynamics such as bifurcating infections, which recently received increased empirical and theoretical attention. Bifurcating infections are characterized by the emergence of two distinct infection types: (i) terminal infections with high pathogen loads resulting in rapid host death, and (ii) persistent infections with lower loads and delayed host death. Here, we propose to use discrete mixture models to perform separate virulence decompositions for each infection type. Using this approach, we reanalysed a recently published experimental dataset on bacterial load and survival in Drosophila melanogaster. This analysis revealed several advantages of the new approach, most importantly the generation of a more comprehensive picture of the varying sources of virulence in different bacterial species. Beyond this application, our approach could provide valuable information for ground-truthing and improving theoretical models of within-host infection dynamics, which are developed to predict variation in infection outcome and pathogen virulence.

'Keeping the kids at home' can limit the persistence of contagious pathogens in social animals.

Social networks are considered to be 'highly modular' when individuals within one module are more connected to each other than they are to individuals in other modules. It is currently unclear how highly modular social networks influence the persistence of contagious pathogens that generate lifelong immunity in their hosts when between-group interactions are age dependent. This trait occurs in social species with communal nurseries, where juveniles are reared together for a substantial period in burrows or similar forms of containment and are thus in isolation from contact with individuals in other social groups. Our main objective was to determine whether, and to what extent, such age-dependent patterns of between-group interactions consistently increased the fade-out probability of contagious pathogens that generate lifelong immunity in their hosts. We hypothesised that in populations of species where juveniles are raised in communal nurseries, a high proportion of recovered adults in a group would form a 'protective barrier' around susceptible juveniles against pathogen transmission, thereby increasing the probability of epidemic fade-out in the population. To test this idea, we implemented a spatially implicit individual-based susceptible-infected-recovered (SIR) model for a large range of generic host and pathogen traits. Our results indicated that (a) the probability of epidemic fade-out was consistently higher in populations with communal nurseries, especially for highly contagious pathogens (high basic reproduction number, R0 ) and (b) communal nurseries can counteract the cost of group living in terms of infection risk to a greater extent than variation in other traits. We discuss our findings in relation to herd immunity and outline the importance of considering the network structure of a given host population before implementing management measures such as vaccinations, since interventions focused on individuals with high between-group contact should be particularly effective for controlling pathogen spread in hosts with communal nurseries.

Diet May Drive Influenza A Virus Exposure in African Mammals.

BACKGROUND: Influenza A viruses (IAVs) represent repeatedly emerging pathogens with near worldwide distribution and an unclear nonavian-host spectrum. While the natural hosts for IAV are among waterfowl species, certain mammals can be productively infected. Southern Africa is home to diverse avian and mammalian fauna for which almost no information exists on IAV dynamics. METHODS: We evaluated 111 serum samples from 14 mammalian species from Namibia for the presence of IAV-specific antibodies and tested whether host phylogeny, sociality, or diet influence viral prevalence and diversity. RESULTS: Free-ranging African mammals are exposed to diverse IAV subtypes. Herbivores developed antibodies against 3 different hemagglutinin (HA) subtypes, at low prevalence, while carnivores showed a higher prevalence and diversity of HA-specific antibody responses against 11 different subtypes. Host phylogeny and sociality were not significantly associated with HA antibody prevalence or subtype diversity. Both seroprevalence and HA diversity were significantly increased in carnivores regularly feeding on birds. CONCLUSIONS: The risk of infection and transmission may be driven by diet and ecological factors that increase contact with migratory and resident waterfowl. Consequently, wild mammals, particularly those that specialize on hunting and scavenging birds, could play an important but overlooked role in influenza epizootics.

A comparison of dominance rank metrics reveals multiple competitive landscapes in an animal society.

Across group-living animals, linear dominance hierarchies lead to disparities in access to resources, health outcomes and reproductive performance. Studies of how dominance rank predicts these traits typically employ one of several dominance rank metrics without examining the assumptions each metric makes about its underlying competitive processes. Here, we compare the ability of two dominance rank metrics-simple ordinal rank and proportional or 'standardized' rank-to predict 20 traits in a wild baboon population in Amboseli, Kenya. We propose that simple ordinal rank best predicts traits when competition is density-dependent, whereas proportional rank best predicts traits when competition is density-independent. We found that for 75% of traits (15/20), one rank metric performed better than the other. Strikingly, all male traits were best predicted by simple ordinal rank, whereas female traits were evenly split between proportional and simple ordinal rank. Hence, male and female traits are shaped by different competitive processes: males are largely driven by density-dependent resource access (e.g. access to oestrous females), whereas females are shaped by both density-independent (e.g. distributed food resources) and density-dependent resource access. This method of comparing how different rank metrics predict traits can be used to distinguish between different competitive processes operating in animal societies.

Higher dominance rank is associated with lower glucocorticoids in wild female baboons: A rank metric comparison.

In vertebrates, glucocorticoid secretion occurs in response to energetic and psychosocial stressors that trigger the hypothalamic-pituitary-adrenal (HPA) axis. Measuring glucocorticoid concentrations can therefore shed light on the stressors associated with different social and environmental variables, including dominance rank. Using 14,172 fecal samples from 237 wild female baboons, we test the hypothesis that high-ranking females experience fewer psychosocial and/or energetic stressors than lower-ranking females. We predicted that high-ranking females would have lower fecal glucocorticoid (fGC) concentrations than low-ranking females. Because dominance rank can be measured in multiple ways, we employ an information theoretic approach to compare 5 different measures of rank as predictors of fGC concentrations: ordinal rank; proportional rank; Elo rating; and two approaches to categorical ranking (alpha vs non-alpha and high-middle-low). Our hypothesis was supported, but it was also too simplistic. We found that alpha females exhibited substantially lower fGCs than other females (typical reduction = 8.2%). If we used proportional rank instead of alpha versus non-alpha status in the model, we observed a weak effect of rank such that fGCs rose 4.2% from the highest- to lowest-ranking female in the hierarchy. Models using ordinal rank, Elo rating, or high-middle-low categories alone failed to explain variation in female fGCs. Our findings shed new light on the association between dominance rank and the stress response, the competitive landscape of female baboons as compared to males, and the assumptions inherent in a researcher's choice of rank metric.

Noninvasive Detection of Equid Herpesviruses in Fecal Samples.

Equid herpesviruses (EHVs) are pathogens of equid and nonequid hosts that can cause disease and fatalities in captivity and in the wild. EHVs establish latent infections but can reactivate, and most EHVs are shed via the nasal passage. Therefore, nasal swabs are generally used for EHV monitoring. However, invasive sampling of wild equids is difficult. While feces is a commonly used substrate for detecting other pathogens, to our knowledge, EHVs have never been detected in feces of naturally infected equids. We systematically tested zebra feces for EHV presence by (i) establishing nested PCR conditions for fecal DNA extracts, (ii) controlling for environmental EHV contamination, and (iii) large-scale testing on a free-ranging zebra population. A dilution minimizing inhibition while maximizing viral DNA concentrations was determined in captive Grévy's zebra (Equus grevyi) fecal samples from individuals shedding EHV nasally. Sixteen of 42 fecal samples (38%) were EHV positive. To demonstrate that the EHV positivity was not a result of environmental contamination, rectal swabs of wild zebras were screened (n = 18 [Equusquagga and E. zebra]), and 50% were EHV positive, indicating that the source of EHV in feces is likely the intestinal mucosa and not postdefecation contamination. Out of 270 fecal samples of wild zebras, 26% were EHV positive. Quantitative PCRs showed that the amount of virus DNA in feces was not significantly smaller than that in other samples. In summary, fecal sampling facilitates large-scale screening and may be useful to noninvasively investigate phylogenetic EHV diversity in wild and domestic equids.IMPORTANCE Equid herpesviruses (EHVs) establish latent infections, and many EHVs are shed and transmitted via nasal discharge primarily through droplet and aerosol infection. Obtaining nasal swabs and other invasive samples from wildlife is often not possible without capture and physical restraint of individuals, which are resource intensive and a health risk for the captured animals. Fecal EHV shedding has never been demonstrated for naturally infected equids. We established the conditions for fecal EHV screening, and our results suggest that testing fecal samples is an effective noninvasive approach for monitoring acute EHV shedding in equids.

The evolution of social learning mechanisms and cultural phenomena in group foragers.

BACKGROUND: Advanced cognitive abilities are widely thought to underpin cultural traditions and cumulative cultural change. In contrast, recent simulation models have found that basic social influences on learning suffice to support both cultural phenomena. In the present study we test the predictions of these models in the context of skill learning, in a model with stochastic demographics, variable group sizes, and evolved parameter values, exploring the cultural ramifications of three different social learning mechanisms. RESULTS: Our results show that that simple forms of social learning such as local enhancement, can generate traditional differences in the context of skill learning. In contrast, we find cumulative cultural change is supported by observational learning, but not local or stimulus enhancement, which supports the idea that advanced cognitive abilities are important for generating this cultural phenomenon in the context of skill learning. CONCLUSIONS: Our results help to explain the observation that animal cultures are widespread, but cumulative cultural change might be rare.

Hormonal correlates of natal dispersal and rank attainment in wild male baboons.

In many mammals, maturational milestones such as dispersal and the attainment of adult dominance rank mark stages in the onset of reproductive activity and depend on a coordinated set of hormonal and socio-behavioral changes. Studies that focus on the link between hormones and maturational milestones are uncommon in wild mammals because of the challenges of obtaining adequate sample sizes of maturing animals and of tracking the movements of dispersing animals. We examined two maturational milestones in wild male baboons-adult dominance rank attainment and natal dispersal-and measured their association with variation in glucocorticoids (fGC) and fecal testosterone (fT). We found that rank attainment is associated with an increase in fGC levels but not fT levels: males that have achieved any adult rank have higher fGC than males that have not yet attained an adult rank. This indicates that once males have attained an adult rank they experience greater energetic and/or psychosocial demands than they did prior to attaining this milestone, most likely because of the resulting participation in both agonistic and sexual behaviors that accompany rank attainment. In contrast, natal dispersal does not produce sustained increases in either fGC or fT levels, suggesting that individuals are either well adapted to face the challenges associated with dispersal or that the effects of dispersal on hormone levels are ephemeral for male baboons.

Skill learning and the evolution of social learning mechanisms.

BACKGROUND: Social learning is potentially advantageous, but evolutionary theory predicts that (i) its benefits may be self-limiting because social learning can lead to information parasitism, and (ii) these limitations can be mitigated via forms of selective copying. However, these findings arise from a functional approach in which learning mechanisms are not specified, and which assumes that social learning avoids the costs of asocial learning but does not produce information about the environment. Whether these findings generalize to all kinds of social learning remains to be established. Using a detailed multi-scale evolutionary model, we investigate the payoffs and information production processes of specific social learning mechanisms (including local enhancement, stimulus enhancement and observational learning) and their evolutionary consequences in the context of skill learning in foraging groups. RESULTS: We find that local enhancement does not benefit foraging success, but could evolve as a side-effect of grouping. In contrast, stimulus enhancement and observational learning can be beneficial across a wide range of environmental conditions because they generate opportunities for new learning outcomes. CONCLUSIONS: In contrast to much existing theory, we find that the functional outcomes of social learning are mechanism specific. Social learning nearly always produces information about the environment, and does not always avoid the costs of asocial learning or support information parasitism. Our study supports work emphasizing the value of incorporating mechanistic detail in functional analyses.

Self-organizing dominance hierarchies in a wild primate population.

Linear dominance hierarchies, which are common in social animals, can profoundly influence access to limited resources, reproductive opportunities and health. In spite of their importance, the mechanisms that govern the dynamics of such hierarchies remain unclear. Two hypotheses explain how linear hierarchies might emerge and change over time. The 'prior attributes hypothesis' posits that individual differences in fighting ability directly determine dominance ranks. By contrast, the 'social dynamics hypothesis' posits that dominance ranks emerge from social self-organization dynamics such as winner and loser effects. While the prior attributes hypothesis is well supported in the literature, current support for the social dynamics hypothesis is limited to experimental studies that artificially eliminate or minimize individual differences in fighting abilities. Here, we present the first evidence supporting the social dynamics hypothesis in a wild population. Specifically, we test for winner and loser effects on male hierarchy dynamics in wild baboons, using a novel statistical approach based on the Elo rating method for cardinal rank assignment, which enables the detection of winner and loser effects in uncontrolled group settings. Our results demonstrate (i) the presence of winner and loser effects, and (ii) that individual susceptibility to such effects may have a genetic basis. Taken together, our results show that both social self-organization dynamics and prior attributes can combine to influence hierarchy dynamics even when agonistic interactions are strongly influenced by differences in individual attributes. We hypothesize that, despite variation in individual attributes, winner and loser effects exist (i) because these effects could be particularly beneficial when fighting abilities in other group members change over time, and (ii) because the coevolution of prior attributes and winner and loser effects maintains a balance of both effects.

How infection-triggered pathobionts influence virulence evolution.

Host-pathogen interactions can be influenced by the host microbiota, as the microbiota can facilitate or prevent pathogen infections. In addition, members of the microbiota can become virulent. Such pathobionts can cause co-infections when a pathogen infection alters the host immune system and triggers dysbiosis. Here we performed a theoretical investigation of how pathobiont co-infections affect the evolution of pathogen virulence. We explored the possibility that the likelihood of pathobiont co-infection depends on the evolving virulence of the pathogen. We found that, in contrast to the expectation from classical theory, increased virulence is not always selected for. For an increasing likelihood of co-infection with increasing pathogen virulence, we found scenario-specific selection for either increased or decreased virulence. Evolutionary changes, however, in pathogen virulence do not always translate into similar changes in combined virulence of the pathogen and the pathobiont. Only in one of the scenarios where pathobiont co-infection is triggered above a specific virulence level we found a reduction in combined virulence. This was not the case when the probability of pathobiont co-infection linearly increased with pathogen virulence. Taken together, our study draws attention to the possibility that host-microbiota interactions can be both the driver and the target of pathogen evolution. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Rapid evolution of cooperation in group-living animals.

BACKGROUND: It is often assumed that evolution takes place on very large timescales. Countering this assumption, rapid evolutionary dynamics are increasingly documented in biological systems, e.g. in the context of predator-prey interactions, species coexistence and invasion. It has also been shown that rapid evolution can facilitate the evolution of cooperation. In this context often evolutionary dynamics influence population dynamics, but in spatial models rapid evolutionary dynamics also emerge with constant population sizes. Currently it is not clear how well these spatial models apply to species in which individuals are not embedded in fixed spatial structures. To address this issue we employ an agent-based model of group living individuals. We investigate how positive assortment between cooperators and defectors and pay-off differences between cooperators and defectors depend on the occurrence of evolutionary dynamics. RESULTS: We find that positive assortment and pay-off differences between cooperators and defectors differ when comparing scenarios with and without selection, which indicates that rapid evolutionary dynamics are occurring in the selection scenarios. Specifically, rapid evolution occurs because changes in positive assortment feed back on evolutionary dynamics, which crucially impacts the evolution of cooperation. At high frequencies of cooperators these feedback dynamics increase positive assortment facilitating the evolution of cooperation. In contrast, at low frequencies of cooperators rapid evolutionary dynamics lead to a decrease in assortment, which acts against the evolution of cooperation. The contrasting dynamics at low and high frequencies of cooperators create positive frequency-dependent selection. CONCLUSIONS: Rapid evolutionary dynamics can influence the evolution of cooperation in group-living species and lead to positive frequency-dependent selection even if population size and maximum group-size are not affected by evolutionary dynamics. Rapid evolutionary dynamics can emerge in this case because sufficiently strong selective pressures allow evolutionary and demographic dynamics, and consequently also feedback between assortment and evolution, to occur on the same timescale. In particular, emerging positive frequency-dependent selection could be an important explanation for differences in cooperative behaviors among different species with similar population structures such as humans and chimpanzees.

Low temperature atomic layer deposition of cobalt using dicobalt hexacarbonyl-1-heptyne as precursor.

In this work, we present the development of an atomic layer deposition (ALD) process for metallic cobalt. The process operates at low temperatures using dicobalt hexacarbonyl-1-heptyne [Co2(CO)6HC≡CC5H11] and hydrogen plasma. For this precursor an ALD window in the temperature range between 50 and 110 °C was determined with a constant deposition rate of approximately 0.1 Å/cycle. The upper limit of the ALD window is defined by the onset of the decomposition of the precursor. In our case, decomposition occurs at temperatures of 125 °C and above, resulting in a film growth in chemical vapour deposition mode. The lower limit of the ALD window is around 35 °C, where the reduction of the precursor is incomplete. The saturation behaviour of the process was investigated. X-ray photoelectron spectroscopy measurements could show that the deposited cobalt is in the metallic state. The finally established process in ALD mode shows a homogeneous coating at the wafer level.

Phylogenetic host specificity and understanding parasite sharing in primates.

Understanding how parasites are transmitted to new species is of great importance for human health, agriculture and conservation. However, it is still unclear why some parasites are shared by many species, while others have only one host. Using a new measure of 'phylogenetic host specificity', we find that most primate parasites with more than one host are phylogenetic generalists, infecting less closely related primates than expected. Evolutionary models suggest that phylogenetic host generalism is driven by a mixture of host-parasite cospeciation and lower rates of parasite extinction. We also show that phylogenetic relatedness is important in most analyses, but fails to fully explain patterns of parasite sharing among primates. Host ecology and geographical distribution emerged as key additional factors that influence contacts among hosts to facilitate sharing. Greater understanding of these factors is therefore crucial to improve our ability to predict future infectious disease risks.

Decomposing virulence to understand bacterial clearance in persistent infections.

Following an infection, hosts cannot always clear the pathogen, instead either dying or surviving with a persistent infection. Such variation is ecologically and evolutionarily important because it can affect infection prevalence and transmission, and virulence evolution. However, the factors causing variation in infection outcomes, and the relationship between clearance and virulence are not well understood. Here we show that sustained persistent infection and clearance are both possible outcomes across bacterial species showing a range of virulence in Drosophila melanogaster. Variation in virulence arises because of differences in the two components of virulence: bacterial infection intensity inside the host (exploitation), and the amount of damage caused per bacterium (per parasite pathogenicity). As early-phase exploitation increased, clearance rates later in the infection decreased, whereas there was no apparent effect of per parasite pathogenicity on clearance rates. Variation in infection outcomes is thereby determined by how virulence - and its components - relate to the rate of pathogen clearance. Taken together we demonstrate that the virulence decomposition framework is broadly applicable and can provide valuable insights into host-pathogen interactions.

The evolution of cooperative turn-taking in animal conflict.

BACKGROUND: A fundamental assumption in animal socio-ecology is that animals compete over limited resources. This view has been challenged by the finding that individuals might cooperatively partition resources by "taking turns". Turn-taking occurs when two individuals coordinate their agonistic behaviour in a way that leads to an alternating pattern in who obtains a resource without engaging in costly fights. Cooperative turn-taking has been largely ignored in models of animal conflict and socio-ecological models that explain the evolution of social behaviours based only on contest and scramble competition. Currently it is unclear whether turn-taking should be included in socio-ecological models because the evolution of turn-taking is not well understood. In particular, it is unknown whether turn-taking can evolve when fighting costs and assessment of fighting abilities are not fixed but emerge from evolved within-fight behaviour. We address this problem with an evolutionary agent-based model. RESULTS: We found that turn-taking evolves for small resource values, alongside a contest strategy that leads to stable dominance relationships. Turn-taking leads to egalitarian societies with unclear dominance relationships and non-linear dominance hierarchies. Evolutionary stability of turn-taking emerged despite strength differences among individuals and the possibility to evolve within-fight behaviour that allows good assessment of fighting abilities. Evolutionary stability emerged from frequency-dependent effects on fitness, which are modulated by feedbacks between the evolution of within-fight behaviour and the evolution of higher-level conflict strategies. CONCLUSIONS: Our results reveal the impact of feedbacks between the evolution of within-fight behaviour and the evolution of higher-level conflict strategies, such as turn-taking. Similar feedbacks might be important for the evolution of other conflict strategies such as winner-loser effects or coalitions. However, we are not aware of any study that investigated such feedbacks. Furthermore, our model suggests that turn-taking could be used by animals to partition low value resources, but to our knowledge this has never been tested. The existence of turn-taking might have been overlooked because it leads to societies with similar characteristics that have been expected to emerge from scramble competition. Analyses of temporal interaction patterns could be used to test whether turn-taking occurs in animals.

How feeding competition determines female chimpanzee gregariousness and ranging in the Taï National Park, Côte d'Ivoire.

Socioecological theory suggests that feeding competition shapes female social relationships. Chimpanzees (Pan troglodytes) live in fission-fusion societies that allow them to react flexibly to increased feeding competition by forming smaller foraging parties when food is scarce. In chimpanzees at Gombe and Kibale, female dominance rank can crucially influence feeding competition and reproductive success as high-ranking females monopolize core areas of relatively high quality, are more gregarious, and have higher body mass and reproductive success than low-ranking females. Chimpanzee females in Taï National Park do not monopolize core areas; they use the entire territory as do the males of their community and are highly gregarious. Although female chimpanzees in Taï generally exhibit a linear dominance hierarchy benefits of high rank are currently not well understood. We used a multivariate analysis of long-term data from two Taï chimpanzee communities to test whether high-ranking females (1) increase gregariousness and (2) minimize their travel costs. We found that high-ranking females were more gregarious than low-rankers only when food was scarce. During periods of food scarcity, high rank allowed females to enjoy benefits of gregariousness, while low-ranking females strongly decreased their gregariousness. High-ranking females traveled more than low-ranking females, suggesting that low-rankers might follow a strategy to minimize energy expenditure. Our results suggest that, in contrast to other chimpanzee populations and depending on the prevailing ecological conditions, female chimpanzees at Taï respond differently to varying levels of feeding competition. Care needs to be taken before generalizing results found in any one chimpanzee population to the species level.

Community structure of domesticated pigs in livestock facilities.

The social structure of animal groups is considered to have an impact on their health and welfare. This could also be true for animals under commercial conditions, but research in this area has been limited. Pigs for example are known to be very social animals, but information about their grouping behavior is mostly derived from wild boars and a limited number of studies in seminatural and commercial conditions. Specifically under commercial conditions it is still unclear to what extent pig herds organize themselves in subgroups and how such group patterns emerge. To answer these questions, we tracked the positions of about 200 sows inside a barn during ongoing production over a period of five weeks and used these data to construct and analyze the animal contact networks. Our analysis showed a very high contact density and only little variation in the number of other animals that a specific animal is in contact with. Nevertheless, in each week we consistently detected three subgroups inside the barn, which also showed a clear spatial separation. Our results show that even in the high density environment of a commercial pig farm, the behavior of pigs to form differentiated groups is consistent with their behavior under seminatural conditions. Furthermore, our findings also imply that the barn layout could play an important role in the formation of the grouping pattern. These insights could be used to monitor and understand the spread of infectious diseases inside the barn better. In addition, our insights could potentially be used to improve the welfare of pigs.

Seasonal host and ecological drivers may promote restricted water as a viral vector.

In climates with seasonally limited precipitation, terrestrial animals congregate at high densities at scarce water sources. We hypothesize that viruses can exploit the recurrence of these diverse animal congregations to spread. In this study, we test the central prediction of this hypothesis - that viruses employing this transmission strategy remain stable and infectious in water. Equid herpesviruses (EHVs) were chosen as a model as they have been shown to remain stable and infectious in water for weeks under laboratory conditions. Using fecal data from wild equids from a previous study, we establish that EHVs are shed more frequently by their hosts during the dry season, increasing the probability of water source contamination with EHV. We document the presence of several strains of EHVs present in high genome copy number from the surface water and sediments of waterholes sampled across a variety of mammalian assemblages, locations, temperatures and pH. Phylogenetic analysis reveals that the different EHV strains found exhibit little divergence despite representing ancient lineages. We employed molecular approaches to show that EHVs shed remain stable in waterholes with detection decreasing with increasing temperature in sediments. Infectivity experiments using cell culture reveals that EHVs remain infectious in water derived from waterholes. The results are supportive of water as an abiotic viral vector for EHV.

Social enhancement can create adaptive, arbitrary and maladaptive cultural traditions.

Many animals are known to learn socially, i.e. they are able to acquire new behaviours by using information from other individuals. Researchers distinguish between a number of different social-learning mechanisms such as imitation and social enhancement. Social enhancement is a simple form of social learning that is among the most widespread in animals. However, unlike imitation, it is debated whether social enhancement can create cultural traditions. Based on a recent study on capuchin monkeys, we developed an agent-based model to test the hypotheses that (i) social enhancement can create and maintain stable traditions and (ii) social enhancement can create cultural conformity. Our results supported both hypotheses. A key factor that led to the creation of cultural conformity and traditions was the repeated interaction of individual reinforcement and social enhancement learning. This result emphasizes that the emergence of cultural conformity does not necessarily require cognitively complex mechanisms such as 'copying the majority' or group norms. In addition, we observed that social enhancement can create learning dynamics similar to a 'copy when uncertain' learning strategy. Results from additional analyses also point to situations that should favour the evolution of learning mechanisms more sophisticated than social enhancement.