Genetic and ‘cultural’ similarity in wild chimpanzees

Abstract

The question of whether animals possess 'cultures' or 'traditions' continues to generate widespread theoretical and empirical interest. Studies of wild chimpanzees have featured prominently in this discussion, as the dominant approach used to identify culture in wild animals was first applied to them. This procedure, the 'method of exclusion,' begins by documenting behavioural differences between groups and then infers the existence of culture by eliminating ecological explanations for their occurrence. The validity of this approach has been questioned because genetic differences between groups have not explicitly been ruled out as a factor contributing to between-group differences in behaviour. Here we investigate this issue directly by analysing genetic and behavioural data from nine groups of wild chimpanzees. We find that the overall levels of genetic and behavioural dissimilarity between groups are highly and statistically significantly correlated. Additional analyses show that only a very small number of behaviours vary between genetically similar groups, and that there is no obvious pattern as to which classes of behaviours (e.g. tool-use versus communicative) have a distribution that matches patterns of betweengroup genetic dissimilarity. These results indicate that genetic dissimilarity cannot be eliminated as playing a major role in generating group differences in chimpanzee behaviour.

The effect of innovation and sex-specific migration on neutral cultural differentiation

“…In this case, patterns of population structure in the behavioural traits are consistent with sex-biased cultural inheritance and migration and a high rate of social learning, but it is not possible to rule out some effect of selection. By contrast, chimpanzees have female-biased dispersal and much lower levels of differentiation in behaviour among groups separated by much greater distances (Whiten et al 1999;Langergraber et al 2011). If the behaviours studied in chimpanzees and vervets are in fact neutrally evolving cultural traits (and this remains an open question), both of these observations are consistent with expectations based on the differences in sex-biased migration.…”

“…Considerable controversy has surrounded the problem of cultural transmission in chimpanzees, as some have argued that observed patterns could also be consistent with a genetic basis for behaviours (Laland & Janik 2006), while additional evidence has been presented based on cladistic analysis suggesting the behaviours are more likely to be culturally inherited (Lycett et al 2007(Lycett et al , 2010. As other research on chimpanzees has failed to find significant differences between patterns of variation among groups for genetic loci versus behavioural traits (Langergraber et al 2011), the extent to which these behaviours are culturally inherited remains unclear. Even assuming many of these traits are culturally inherited, there is little understanding of why they are present in some groups but not in others.…”

“…Similarity between F ST for genetic loci versus behavioural traits is expected even if the trait is culturally inherited under many demographic scenarios (as suggested by Langergraber et al 2011). On the other hand, even if pronounced differences in genetic versus putative cultural F ST are found, this could be explained by natural selection affecting a genetically determined behavioural trait, either through spatially homogeneous selection (low F ST ) or heterogeneous selection (high F ST ), as discussed with respect to Q ST in quantitative genetic traits (Spitze 1993;Whitlock 2008).…”

“…Coupling comparisons of population structure in neutral markers versus behavioural traits (e.g. Langergraber et al 2011) with studies of covariance in kinship and behavioural variants (e.g. Krützen et al 2005) could provide a more powerful method to differentiate between an innate genetic basis and social learning.…”

“…Explicitly applying an approach using F ST to study population structure, where frequencies of alleles (genetic markers) are replaced by abundance frequencies of cultural traits (cultural markers), could increase the power of studies that have relied on comparisons of patterns of variation among groups averaged over many traits (in the absence of data on variance among individuals within groups, e.g. Langergraber et al 2011).…”