When can cultural selection explain adaptation?

Cultural selection models aim to explain cultural phenomena as the products of a selective process, often characterising institutions, practices, norms or behaviours as adaptations. I argue that a lack of attention has been paid to the explanatory power of cultural selection frameworks. Arguments for cultural selection frequently depend on demonstrating only that selection models can in principle be applied to culture, rather than explicitly demonstrating the explanatory payoffs that could arise from their application. Understanding when and how cultural selection generates powerful explanations is crucial to evaluating cultural selection, as well as realising its promised epistemic and practical benefits. I argue that the ability for cultural selection to explain ‘design without a designer’ is crucial to successful and powerful cultural selection explanations. I introduce the strategy of comparing cultural selection to goal-directed agent accounts in order to evaluate when cultural selection can provide distinctive explanatory payoffs, drawing on two case studies to illustrate the benefits of this strategy. I argue that a focus on phenomena which cannot be explained through intention or agency-based explanations in particular could provide a fruitful avenue to identifying the cases where cultural selection can be insightfully applied.

Selecting for Celibacy: Cultural Evolution and the Puzzling Case of Buddhist Celibacy

<p>Buddhist celibacy provides an example of religious behaviour which appears puzzling from the vantage point of genetic selection, but whose maintenance can be partially explained because of the dynamics of cultural selection. In this thesis, I examine how and why celibacy is maintained and perpetuated within Buddhism and how this relates to the explanations cultural selection offers for costs within groups. I argue that celibacy is adaptive because it divides Buddhist communities into two parts, stimulating innate tendencies towards in-group cooperation without the need for an outside group. Because Buddhist celibates are also materially non-productive their presence necessitates increased cooperative behaviours in lay communities. I argue that the endurance of the parts of Buddhist traditions which are necessary to maintaining celibate practise provides evidence that cultural selection has shaped the tradition to perpetuate and reinforce celibacy, a behaviour which is adaptive because it promotes cooperative behaviours within a divided cultural group. Celibacy increases the cultural fitness of Buddhist communities.</p>

Selecting for Celibacy: Cultural Evolution and the Puzzling Case of Buddhist Celibacy

<p>Buddhist celibacy provides an example of religious behaviour which appears puzzling from the vantage point of genetic selection, but whose maintenance can be partially explained because of the dynamics of cultural selection. In this thesis, I examine how and why celibacy is maintained and perpetuated within Buddhism and how this relates to the explanations cultural selection offers for costs within groups. I argue that celibacy is adaptive because it divides Buddhist communities into two parts, stimulating innate tendencies towards in-group cooperation without the need for an outside group. Because Buddhist celibates are also materially non-productive their presence necessitates increased cooperative behaviours in lay communities. I argue that the endurance of the parts of Buddhist traditions which are necessary to maintaining celibate practise provides evidence that cultural selection has shaped the tradition to perpetuate and reinforce celibacy, a behaviour which is adaptive because it promotes cooperative behaviours within a divided cultural group. Celibacy increases the cultural fitness of Buddhist communities.</p>

The Shortlist Effect: Nestedness contributions as a tool to explain cultural success

Detecting the forces behind the success or failure of cultural products, such as books or films, remains a challenge. Three such forces are drift, context-biased selection, and selection based on content—when things succeed because of their intrinsic appeal. We propose a tool to study content-biased selection in sets of cultural collections—e.g. libraries or movie collections — based on the “shortlist effect”: the fact that smaller collections are more selective, more likely to favour highly appealing items over others. We use a model to show that, when the shortlist effect is at work, content-biased cultural selection is associated with greater nestedness in sets of collections. Having established empirically the existence of the shortlist effect, and of content-biased selection, in 28 sets of movie collections, we show that nestedness contributions can be used to estimate to what extent specific movies owe their success to their intrinsic properties. This method can be used in a wide range of datasets to detect the items that owe their success to their intrinsic appeal, as opposed to “hidden gems” or “accidental hits”.

Maintenance of prior behaviour can enhance cultural selection

Many cultural phenomena evolve through a Darwinian process whereby adaptive variants are selected and spread at the expense of competing variants. While cultural evolutionary theory emphasises the importance of social learning to this process, experimental studies indicate that people’s dominant response is to maintain their prior behaviour. In addition, while payoff-biased learning is crucial to Darwinian cultural evolution, learner behaviour is not always guided by variant payoffs. Here, we use agent-based modelling to investigate the role of maintenance in Darwinian cultural evolution. We vary the degree to which learner behaviour is payoff-biased (i.e., based on critical evaluation of variant payoffs), and compare three uncritical (non-payoff-biased) strategies that are used alongside payoff-biased learning: copying others, innovating new variants, and maintaining prior variants. In line with previous research, we show that some level of payoff-biased learning is crucial for populations to converge on adaptive cultural variants. Importantly, when combined with payoff-biased learning, uncritical maintenance leads to stronger population-level adaptation than uncritical copying or innovation, highlighting the importance of maintenance to cultural selection. This advantage of maintenance as a default learning strategy may help explain why it is a common human behaviour.

Human self-selection as a mechanism of human societal evolution: A critique of the cultural selection argument

Natural selection is the main mechanism that drives the evolution of species, including human societies. Under natural selection, human species responds through genetic and cultural adaptations to internal and external selection pressures for survival and reproductive success. However, this theory is ineffective in explaining human societal evolution in the Holocene and a cultural selection argument has been made to remedy the theory. The present article provides a critique of the cultural selection argument and proposes an alternative conception that treats human self-selection as an emergent mechanism of human societal evolution characterized by a new type of selection pressure and a separate fitness criterion. Specifically, the evolution of human societies is divided into two major periods, each driven by a different mode of selection: natural selection acting on genes and cultures for survival and reproductive success prior to the Neolithic Revolution, and human self-selection acting on cultures – and potentially genes as well – for thrival and prosperous living after the Neolithic Revolution. The conditions for the transition from the first mode of selection to the second and the implications of this transition for social research are also discussed.

Uniqueness in the life sciences: how did the elephant get its trunk?

Researchers in the life sciences often make uniqueness attributions; about branching events generating new species, the developmental processes generating novel traits and the distinctive cultural selection pressures faced by hominins. Yet since uniqueness implies non-recurrence, such attributions come freighted with epistemic consequences. Drawing on the work of Aviezer Tucker, we show that a common reaction to uniqueness attributions is pessimism: both about the strength of candidate explanations as well as the ability to even generate such explanations. Looking at two case studies—elephant trunks and human teaching—we develop a more optimistic account. As we argue, uniqueness attributions are revisable claims about the availability of several different kinds of comparators. Yet even as researchers investigate the availability of such comparators, they are able to mobilize complex sets of empirical and theoretical tools. Rather than hindering scientific investigation, then, we argue that uniqueness attributions often spur the generation of a range of epistemic goods.

Population turnover facilitates cultural selection for efficiency in birds

Culture, defined as socially transmitted information and behaviors that are shared in groups and persist over time, is increasingly accepted to occur across a wide range of taxa and behavioral domains. While persistent, cultural traits are not necessarily static, and their distribution can change in frequency and type in response to selective pressures, analogous to that of genetic alleles. This has lead to the treatment of culture as an evolutionary process, with cultural evolutionary theory arguing that culture exhibits the three fundamental components of Darwinian evolution: variation, competition, and inheritance. Selection for more efficient behaviors over alternatives is a crucial component of cumulative cultural evolution, yet our understanding of how and when such cultural selection occurs in non-human animals is limited. We performed a cultural diffusion experiment using 18 captive populations of wild-caught great tits (Parus major) to ask whether more efficient foraging traditions are selected for, and whether this process is affected by a fundamental demographic process—population turnover. Our results showed that gradual replacement of individuals with naive immigrants greatly increased the probability that a more efficient behavior invaded a population’s cultural repertoire and out-competed an established inefficient behavior. Fine-scale, automated behavioral tracking revealed that turnover did not increase innovation rates, but instead acted on adoption rates, as immigrants disproportionately sampled novel, efficient behaviors relative to available social information. These results provide strong evidence for cultural selection for efficiency in animals, and highlight the mechanism that links population turnover to this process.