The evolution of cultural adaptations: Fijian food taboos protect against dangerous marine toxins

Abstract

The application of evolutionary theory to understanding the origins of our species' capacities for social learning has generated key insights into cultural evolution. By focusing on how our psychology has evolved to adaptively extract beliefs and practices by observing others, theorists have hypothesized how social learning can, over generations, give rise to culturally evolved adaptations. While much field research documents the subtle ways in which culturally transmitted beliefs and practices adapt people to their local environments, and much experimental work reveals the predicted patterns of social learning, little research connects real-world adaptive cultural traits to the patterns of transmission predicted by these theories. Addressing this gap, we show how food taboos for pregnant and lactating women in Fiji selectively target the most toxic marine species, effectively reducing a woman's chances of fish poisoning by 30 per cent during pregnancy and 60 per cent during breastfeeding. We further analyse how these taboos are transmitted, showing support for cultural evolutionary models that combine familial transmission with selective learning from locally prestigious individuals. In addition, we explore how particular aspects of human cognitive processes increase the frequency of some non-adaptive taboos. This case demonstrates how evolutionary theory can be deployed to explain both adaptive and non-adaptive behavioural patterns.

Figure 1.

Taboos reported by women for 17 types of food during pregnancy (n = 70) and breastfeeding (n = 61). The error bars are 95% exact confidence intervals. Dark grey bars, breastfeeding; light grey bars, pregnancy.

Figure 2.

Distribution of reports about how women learned their food taboos. Error bars are 95% exact confidence intervals.

Figure 3.

Network for yalewa vuku. The nodes represent villagers, with the circles indicating females and the squares males. Each arrow points from the person interviewed to one of the individuals named. The colours of the nodes distinguish the two villages. The size of the node is proportional to its indegree centrality, which is the total of individuals who selected the node as a yalewa vuku.

Figure 4.

Higher level categorization for eight folkspecies. Error bars are 95% exact CI (n = 140). Black bars, ika; light grey bars, manumanu; white bars, vivili; dark grey bars, vatu.