Abstract
Intergroup variation (IGV) refers to variation between different groups of the same species. While its existence in the behavioural realm has been expected and evidenced, the potential effects of IGV are rarely considered in studies that aim to shed light on the evolutionary origins of human socio-cognition, especially in our closest living relatives—the great apes. Here, by taking chimpanzees as a point of reference, we argue that (i) IGV could plausibly explain inconsistent research findings across numerous topics of inquiry (experimental/behavioural studies on chimpanzees), (ii) understanding the evolutionary origins of behaviour requires an accurate assessment of species' modes of behaving across different socio-ecological contexts, which necessitates a reliable estimation of variation across intraspecific groups, and (iii) IGV in the behavioural realm is increasingly likely to be expected owing to the progressive identification of non-human animal cultures. With these points, and by extrapolating from chimpanzees to generic guidelines, we aim to encourage researchers to explicitly consider IGV as an explanatory variable in future studies attempting to understand the socio-cognitive and evolutionary determinants of behaviour in group-living animals.
Highlights
Within the order of primates, humans are the species occupying the widest range of habitats, spanning from small-scale societies in subarctic climates to cities with millions of inhabitants in desert environments
While its existence in the behavioural realm has been expected and evidenced, the potential effects of Intergroup variation (IGV) are rarely considered in studies that aim to shed light on the evolutionary origins of human socio-cognition, especially in our closest living relatives—the great apes
By taking chimpanzees as a point of reference, we argue that (i) IGV could plausibly explain inconsistent research findings across numerous topics of inquiry, (ii) understanding the evolutionary origins of behaviour requires an accurate assessment of species’ modes of behaving across different socio-ecological contexts, which necessitates a reliable estimation of variation across intraspecific groups, and (iii) IGV in the behavioural realm is increasingly likely to be expected owing to the progressive identification of non-human animal cultures
Summary
Within the order of primates, humans are the species occupying the widest range of habitats, spanning from small-scale societies in subarctic climates to cities with millions of inhabitants in desert environments. The importance of considering cross-cultural variation for understanding universals and diversity in human cognition and behaviour has gained increasing traction over the past years Intergroup variation (: ‘IGV’) is becoming an integrated level of explanation of behavioural diversity in the human species, especially with regard to social behaviour. Already in the same PNAS issue, there is one study highlighting that groups of chimpanzees differ from one another in their social dynamics, despite experiencing similar socioecological conditions [12]. In the light of the increasing evidence suggestive of the presence of group differences in the social behaviour of animals [13,14,15,16]), we believe a similar cautioning—i.e. against the implicit assumption that individuals of the same species share a uniform psychology—is justified for the study of animal behaviour. We outline a pragmatic protocol for constructively incorporating the effects of IGV in animal studies
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