On the nature of cultural transmission networks: evidence from Fijian villages for adaptive learning biases

Abstract

Unlike other animals, humans are heavily dependent on cumulative bodies of culturally learned information. Selective processes operating on this socially learned information can produce complex, functionally integrated, behavioural repertoires-cultural adaptations. To understand such non-genetic adaptations, evolutionary theorists propose that (i) natural selection has favoured the emergence of psychological biases for learning from those individuals most likely to possess adaptive information, and (ii) when these psychological learning biases operate in populations, over generations, they can generate cultural adaptations. Many laboratory experiments now provide evidence for these psychological biases. Here, we bridge from the laboratory to the field by examining if and how these biases emerge in a small-scale society. Data from three cultural domainsfishing, growing yams and using medicinal plants-show that Fijian villagers (ages 10 and up) are biased to learn from others perceived as more successful/knowledgeable, both within and across domains (prestige effects). We also find biases for sex and age, as well as proximity effects. These selective and centralized oblique transmission networks set up the conditions for adaptive cultural evolution.Keywords: cultural transmission; networks; prestige-biased transmission; dual inheritance theory; Fiji; cultural adaptations EVIDENCE FROM FIJIAN VILLAGES FOR ADAPTIVE LEARNING BIASESLong before agriculture and the emergence of complex societies, humans with the same basic genetic endowments expanded across the globe into a dizzying range of environments, from the arid deserts of Australia to the frozen tundra of Alaska. Survival in this range of environments, many of which are ill-suited for a tropical primate like us, depends on large bodies of culturally transmitted practices, beliefs, values and know-how. Examples include the (i) complicated manufacturing processes for arrow poisons, bows, traps, blowguns and kayaks; (ii) complex practices to detoxify critical food sources, such as acorns, cycads and cassava [1,2] or to release essential nutrients from plants [3]; (iii) taboo repertoires that protect mothers and their offspring from dangerous marine toxins [4]; and (iv) recipes and taste preferences for antimicrobial spices that reduce pathogen threats posed by meat in warm climates [5,6]. Such cultural products appear functionally well-designed to address local environmental challenges, usually in subtle ways not recognized or explicitly understood by the people reliant on them. Such anthropological observations mean that understanding the nature and success of our species requires explaining the emergence of such cultural adaptations [7].To approach this issue, we draw on work applying evolutionary thinking to understanding culture and cultural change. This enterprise can be partitioned into three inter-related lines of research. The first involves applying evolutionary reasoning, often aided by the construction of formal models, to generate hypotheses about how n...

Evaluating reproductive decisions as discrete choices under social influence

“…Transparent social influence might come from an acknowledged village expert in a particular category [31], whereas less-intense influence might diffuse among passive members of village social networks, who might not necessarily adopt the behaviour themselves [32]. Among over 20 high-fertility communities in rural Poland, for example, Colleran et al [16] found that the low-fertility norms of educated women were learned socially by lesser educated women within the same social networks who were using the more-educated women as models.…”

Culture evolves

“…Articles in several parts of this issue (e.g. [2,5,6,25,37,50,51]) describe experimental evidence that rules such as 'conform to the majority behaviour', 'copy the most successful individual' and 'learn from familiar individuals' are used by a range of distantly related animals, as well as humans, although differing underlying processes may be involved.…”

“…[2,31,35,37,51]) draw on this tradition. Moreover, we have opted to focus here on culture per se, at the cost of neglecting the larger subject of gene -culture coevolution.…”

“…Henrich & Broesch [37] provide a complementary analysis of cultural adaptation, building on the extensive foundations provided by the modelling literature discussed by Shennan [31], to which Henrich has made extensive contributions (e.g. [78]).…”

“…Two papers in part 4 provide convergent evidence for such selectivity (see also [37]). Hewlett et al [50] provide the first detailed observational evidence for such learning biases among children growing up in hunter-gatherer communities, while Harris and Corriveau [51] use experimental procedures to demonstrate the early emergence and developmental time-course of such biases.…”