Horizontal Cultural Transmission Research Articles

Cultural transmission based multi-objective evolution strategy for evolutionary multitasking

In recent years, many efficient evolutionary multitasking (EMT) algorithms have been proposed to solve multi-objective multi-task optimization problems. However, EMT algorithms often face negative transfer problems. In this paper, a novel multi-objective evolution strategy, called CT-EMT-MOES, is proposed based on a cultural transmission theory for solving multi-objective multitask optimization problems. First, two evolutionary operators inspired by cultural transmission theory are proposed. The elite-guided variation strategy can transfer the information from the current Pareto front to all individuals and guide the population to quickly converge. The horizontal cultural transmission strategy can efficiently transfer information from the source task to the target task. Second, to solve the negative transfer problem, an adaptive information transfer strategy is proposed to adaptively adjust the probability of an information transfer. Third, the proposed algorithm can gain a Pareto front with good convergence and diversity by utilizing a smaller population size and fewer computing resources. As a result, the proposed algorithm can effectively utilize the implicit similarity and complementarity between simultaneous optimized tasks to improve the overall convergence efficiency and reduce a negative transfer. Finally, comprehensive experimental results show that the proposed algorithm can achieve a better performance compared with previous state-of-the-art multi-objective EMT algorithms.

The role of vocal learning in call acquisition of wild grey seal pups.

Pinnipeds have been identified as one of the best available models for the study of vocal learning. Experimental evidence for their learning skills is demonstrated with advanced copying skills, particularly in formant structure when copying human speech sounds and melodies. By contrast, almost no data are available on how learning skills are used in their own communication systems. We investigated the impact of playing modified seal sounds in a breeding colony of grey seals (Halichoerus grypus) to study how acoustic input influenced vocal development of eight pups. Sequences of two or three seal pup calls were edited so that the average peak frequency between calls in a sequence changed up or down. We found that seals copied the specific stimuli played to them and that copies became more accurate over time. The differential response of different groups showed that vocal production learning was used to achieve conformity, suggesting that geographical variation in seal calls can be caused by horizontal cultural transmission. While learning of pup calls appears to have few benefits, we suggest that it also affects the development of the adult repertoire, which may facilitate social interactions such as mate choice.This article is part of the theme issue ‘Vocal learning in animals and humans’.

Front propagation and cultural transmission. Theory and application to Neolithic transitions

• Invasion of a population that incorporates individuals of a pre-existing population. • First model of oblique transmission (acculturation by older individuals). • Oblique transmission is the most powerful mechanism (fastest fronts). • Example of a Neolithic front can be only explained by oblique transmission. • We obtain bounds on the intensity of cultural transmission. We study the front propagation of a population that incorporates individuals of a second, pre-existing population. Previous models of such incorporation deal only with vertical cultural transmission (interbreeding) and horizontal cultural transmission (acculturation of individuals of the second population by members of the first one and of similar age). Here we present the first model of oblique transmission (acculturation by individuals of an older generation), which is more complicated because a model with age structure is necessary. We compare the new, age-structured model for oblique, horizontal and vertical transmission. The most powerful mechanism (fastest fronts) is oblique transmission. Two illustrative applications of Neolithic front propagation are presented. In one of them, the front was so fast that neither horizontal nor vertical transmission can explain it (but oblique transmission can). In the cases for which cultural transmission is a viable explanation, the observed front speed yields bounds on the intensity of cultural transmission. Our models are also of interest in many other Neolithic and non-Neolithic human range expansions, including major human migrations. Additionally, in future work the new age-structured models reported in this paper could be applied to model genetic gradients and, possibly, to similar phenomena in other species in which cultural transmission is well-known to occur.

Causes and consequences of female centrality in cetacean societies.

Cetaceans are fully aquatic predatory mammals that have successfully colonized virtually all marine habitats. Their adaptation to these habitats, so radically different from those of their terrestrial ancestors, can give us comparative insights into the evolution of female roles and kinship in mammalian societies. We provide a review of the diversity of such roles across the Cetacea, which are unified by some key and apparently invariable life-history features. Mothers are uniparous, while paternal care is completely absent as far as we currently know. Maternal input is extensive, lasting months to many years. Hence, female reproductive rates are low, every cetacean calf is a significant investment, and offspring care is central to female fitness. Here strategies diverge, especially between toothed and baleen whales, in terms of mother-calf association and related social structures, which range from ephemeral grouping patterns to stable, multi-level, societies in which social groups are strongly organized around female kinship. Some species exhibit social and/or spatial philopatry in both sexes, a rare phenomenon in vertebrates. Communal care can be vital, especially among deep-diving species, and can be supported by female kinship. Female-based sociality, in its diverse forms, is therefore a prevailing feature of cetacean societies. Beyond the key role in offspring survival, it provides the substrate for significant vertical and horizontal cultural transmission, as well as the only definitive non-human examples of menopause. This article is part of the theme issue 'The evolution of female-biased kinship in humans and other mammals'.

Estimating the relative importance of demic and cultural diffusion in the spread of the Neolithic in Scandinavia.

Using a database of early farming sites in Scandinavia, we estimate that the spread rate of the Neolithic was in the range 0.44–0.66 km yr−1. This is substantially slower (by about 50%) than the rate in continental Europe. We interpret this result in the framework of a new mathematical model that includes horizontal cultural transmission (acculturation), vertical cultural transmission (interbreeding) and demic diffusion (reproduction and dispersal of farmers). To parametrize the model, we estimate reproduction rates of early farmers using archaeological data (sum-calibrated probabilities for the dates of early Neolithic Scandinavian sites) and use them in a wave-of-advance model for the first time. Comparing the model with the archaeological data, we find that the percentage of the spread rate due to cultural diffusion is below 50% (except for very extreme parameter values, and even for them it is below 54%). This strongly suggests that the spread of the Neolithic in Scandinavia was driven mainly by demic diffusion. This conclusion, obtained from archaeological data, agrees qualitatively with the implications of ancient genetic data, but the latter are yet too few in Scandinavia to produce any quantitative percentage for the spread rate due to cultural diffusion. We also find that, on average, fewer than eight hunter–gatherers were incorporated in the Neolithic communities by each group of 10 pioneering farmers, via horizontal and/or vertical cultural transmission.

Correction: How Do People Become W.E.I.R.D.? Migration Reveals the Cultural Transmission Mechanisms Underlying Variation in Psychological Processes.

[This corrects the article DOI: 10.1371/journal.pone.0147162.].

Mate-choice copying: A fitness-enhancing behavior that evolves by indirect selection.

A spatially explicit, individual-based simulation model is used to study the spread of an allele for mate-choice copying (MCC) through horizontal cultural transmission when female innate preferences do or do not coevolve with a male viability-increasing trait. Evolution of MCC is unlikely when innate female preferences coevolve with the trait, as copier females cannot express a higher preference than noncopier females for high-fitness males. However, if a genetic polymorphism for innate preference persists in the population, MCC can evolve by indirect selection through hitchhiking: the copying allele hitchhikes on the male trait. MCC can be an adaptive behavior-that is, a behavior that increases a population's average fitness relative to populations without MCC-even though the copying allele itself may be neutral or mildly deleterious.

How Do People Become W.E.I.R.D.? Migration Reveals the Cultural Transmission Mechanisms Underlying Variation in Psychological Processes.

Cultural psychologists have shown that people from Western, Educated, Industrialised, Rich, Democratic (WEIRD) countries often exhibit different psychological processing to people from less-WEIRD countries. The former exhibit more individualistic and less collectivistic social orientation, and more analytic and less holistic cognition, than non-Westerners. Yet the mechanisms responsible for maintaining this cultural variation are unclear. Immigration is an ideal ‘natural experiment’ for uncovering such mechanisms. We used a battery of psychological measures previously shown to vary cross-culturally to compare the social orientation and cognitive style of 286 residents of East London from three cultural backgrounds: (i) 1st-generation British Bangladeshi immigrants; (ii) 2nd-generation British Bangladeshis raised in the UK to Bangladeshi-raised parents; and (iii) non-migrants whose parents were born and raised in the UK. Model comparison revealed that individualism and dispositional attribution, typical of Western societies, are driven primarily by horizontal cultural transmission (e.g. via mass media), with parents and other family members having little or no effect, while collectivism, social closeness and situational attribution were driven by a mix of vertical/oblique cultural transmission (e.g. via family contact) and horizontal cultural transmission. These individual-level transmission dynamics can explain hitherto puzzling population-level phenomena, such as the partial acculturation of 2nd-generation immigrants on measures such as collectivism (due to the mix of vertical and horizontal cultural transmission), or the observation in several countries of increasing individualism (which is transmitted horizontally and therefore rapidly) despite little corresponding change in collectivism (which is transmitted partly vertically and therefore more slowly). Further consideration of cultural transmission mechanisms, in conjunction with the study of migrant communities and model comparison statistics, can shed light on the persistence of, and changes in, culturally-variable psychological processes.

Phylogenetic analysis of Polynesian ritual architecture suggests extensive cultural sharing and innovation

Ritual architecture across Polynesia displays similarities that are evidence of populations' shared ancestry and interaction. Examination of ritual architecture traits - the design of courtyards, the use of uprights and sacrificial pits, the placement of walls and altars - has, for well over a century, contributed to hypotheses concerning the relatedness of different Polynesian groups and the transmission of ritual behaviours across islands and archipelagos. The research presented here follows this tradition and considers these traits from a quantitative phylogenetic perspective designed to generate hypotheses about the cultural relatedness of ritual architecture classes. Cladistics, a technique specifically designed to arrange classes into hierarchical patterns of relatedness, is presented and then used to construct cultural phylogenies of 198 pieces of ritual architecture from across East Polynesia. The cladistic analyses produce only very limited support for specific phylogenetic relationships between island and archipelago populations and instead suggest Polynesian ritual architectural variation is a product of both extensive horizontal cultural transmission or sharing and high levels of architectural trait innovation.

Humpback Whale Song on the Southern Ocean Feeding Grounds: Implications for Cultural Transmission

Male humpback whales produce a long, complex, and stereotyped song on low-latitude breeding grounds; they also sing while migrating to and from these locations, and occasionally in high-latitude summer feeding areas. All males in a population sing the current version of the constantly evolving display and, within an ocean basin, populations sing similar songs; however, this sharing can be complex. In the western and central South Pacific region there is repeated cultural transmission of song types from eastern Australia to other populations eastward. Song sharing is hypothesized to occur through several possible mechanisms. Here, we present the first example of feeding ground song from the Southern Ocean Antarctic Area V and compare it to song from the two closest breeding populations. The early 2010 song contained at least four distinct themes; these matched four themes from the eastern Australian 2009 song, and the same four themes from the New Caledonian 2010 song recorded later in the year. This provides evidence for at least one of the hypothesized mechanisms of song transmission between these two populations, singing while on shared summer feeding grounds. In addition, the feeding grounds may provide a point of acoustic contact to allow the rapid horizontal cultural transmission of song within the western and central South Pacific region and the wider Southern Ocean.

Is killer whale dialect evolution random?

The killer whale is among the few species in which cultural change accumulates over many generations, leading to cumulative cultural evolution. Killer whales have group-specific vocal repertoires which are thought to be learned rather than being genetically coded. It is supposed that divergence between vocal repertoires of sister groups increases gradually over time due to random learning mistakes and innovations. In this case, the similarity of calls across groups must be correlated with pod relatedness and, consequently, with each other. In this study we tested this prediction by comparing the patterns of call similarity between matrilines of resident killer whales from Eastern Kamchatka. We calculated the similarity of seven components from three call types across 14 matrilines. In contrast to the theoretical predictions, matrilines formed different clusters on the dendrograms made by different calls and even by different components of the same call. We suggest three possible explanations for this phenomenon. First, the lack of agreement between similarity patterns of different components may be the result of constraints in the call structure. Second, it is possible that call components change in time with different speed and/or in different directions. Third, horizontal cultural transmission of call features may occur between matrilines.

Dynamic Horizontal Cultural Transmission of Humpback Whale Song at the Ocean Basin Scale

Cultural transmission, the social learning of information or behaviors from conspecifics, is believed to occur in a number of groups of animals, including primates, cetaceans, and birds. Cultural traits can be passed vertically (from parents to offspring), obliquely (from the previous generation via a nonparent model to younger individuals), or horizontally (between unrelated individuals from similar age classes or within generations). Male humpback whales (Megaptera novaeangliae) have a highly stereotyped, repetitive, and progressively evolving vocal sexual display or "song" that functions in sexual selection (through mate attraction and/or male social sorting). All males within a population conform to the current version of the display (song type), and similarities may exist among the songs of populations within an ocean basin. Here we present a striking pattern of horizontal transmission: multiple song types spread rapidly and repeatedly in a unidirectional manner, like cultural ripples, eastward through the populations in the western and central South Pacific over an 11-year period. This is the first documentation of a repeated, dynamic cultural change occurring across multiple populations at such a large geographic scale.

The influence of social niche on cultural niche construction: modelling changes in belief about marriage form in Taiwan

With introduction of social niche effects into a model of cultural change, the frequency of a practice cannot predict the frequency of its underlying belief. The combination of a general model with empirical data from a specific case illustrates the importance of collaboration between modellers and field researchers, and identifies the type of quantitative data necessary for analysing case studies. Demographic data from colonial-period household registers in Taiwan document a shift in marriage form within 40 years, from a mixture of uxorilocal marriages and virilocal marriages to the latter's dominance. Ethnographic data indicate marriage-related beliefs, costs, ethnic effects and colonial policies as well as the importance of horizontal cultural transmission. We present a formal model for the effects of moral beliefs about marriage and a population economic index on the decline of uxorilocal marriage. We integrate empirical marriage rates and an estimated economic index to produce five projections of the historical frequencies of one belief. These projections demonstrate how economic development may affect a cultural niche. They also indicate the need for future research on the relationship between wealth and cultural variability, the motivational force of cultural versus social factors, and the process of cultural niche construction.

The Cultural Transmission of Great Basin Projectile-Point Technology I: An Experimental Simulation

A Darwinian evolutionary approach to archaeology naturally leads to a focus on cultural transmission. Theoretical models of cultural evolution indicate that individual-level details of cultural transmission can have specific and significant population-level effects, implying that differences in transmission may be detectable in the archaeological record. Here we present an experimental simulation of the cultural transmission of prehistoric projectile-point technology, simulating the two transmission modes-indirect bias and guided variation-that Bettinger and Eerkens (1999) suggested were responsible for differences in Nevada and California point-attribute correlations. Groups of participants designed “virtual projectile points” and tested them in “virtual hunting environments,” with different phases of learning simulating, alternately, indirectly biased cultural transmission and independent individual learning. As predicted, periods of cultural transmission were associated with significantly stronger attribute correlations than were periods of individual learning. We also found that participants who could engage in indirectly biased horizontal cultural transmission outperformed individual-learning controls, especially when individual learning was costly and the selective environment was multimodal. The study demonstrates that experimental simulations of cultural transmission, used alongside archaeological data, mathematical models and computer simulations, constitute a useful tool for studying cultural change.

Behavioral evolution and biocultural games: Oblique and horizontal cultural transmission

We consider an evolutionary game model in which strategies are culturally transmitted among individuals rather than inherited biologically. In addition to vertical transmission (from parents to offspring), we investigate the effects of oblique (from members of the parental generation to offspring) and horizontal (among age peers) transmission on game dynamics. Our study yields two important results. Firstly, biocultural games show a greater diversity of dynamical behaviors than their purely biological counterparts, including multiple fully polymorphic equilibria. Secondly, biocultural games on average show greater equilibrium strategy diversity. These results suggest that cultural transmission in the presence of natural selection may be an important mechanism maintaining behavioral diversity in natural populations.