The animal cultures debate: response to Laland and Janik

Abstract

In their recent article in TREE [ 1 Laland K.N. Janik V. The animal cultures debate. Trends Ecol. Evol. 2006; 21: 542-547 Abstract Full Text Full Text PDF PubMed Scopus (289) Google Scholar ], Laland and Janik discuss a series of concerns about the investigation of wild animal culture. One of these is the usefulness of what they call the ‘ethnographic’ technique (which we prefer to call more straightforwardly the method of exclusion) because its use would imply that culture alone is responsible for geographical variation in behaviour. However, the purpose of the method of exclusion is to identify the presence of cultures in wild animal populations per se, and not, as Laland and Janik argue, to estimate the relative importance of culture in geographical variation in behaviour. Those who have applied the method often stress the contribution of genetic and ecological differences between populations in bringing about behavioural differences between them. Indeed, most are ethologists, in the tradition of Hinde and Kummer, who noted decades ago that a genetic–learned dichotomy makes no sense in relation to a particular episode or category of behaviour, but can logically apply to a ‘dichotomy of differences’, which is exactly the point of the method of exclusion: a difference in behaviour between two populations could be caused only by social learning and not by either genetics or individual learning. Thus, demonstrating only a few cases suffices to establish a role for social learning in those cases where ecological and/or genetic variation is also found. Genetic differences among populations or individuals are unlikely to account for various well-documented cases of behavioural geographical variation, because of the disjunct, checkerboard pattern of the presence and absence of a particular technique, such as nut cracking by chimpanzees Pan troglodytes vellerosus [ 2 Morgan B.J. Abwe E.E. Chimpanzees use stone hammers in Cameroon. Curr. Biol. 2006; 16: R632-R633 Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar ] or seed extraction from Neesia fruits by orang-utans Pongo abelii [ 3 Van Schaik C. Why are some animals so smart?. Sci. Am. 2006; 294: 64-71 Crossref PubMed Scopus (26) Google Scholar ]. Meanwhile, recent experiments in captive chimpanzees [ 4 Horner V. et al. Faithful replication of foraging techniques along cultural transmission chains by chimpanzees and children. Proc. Natl. Acad. Sci. U. S. A. 2006; 103: 13878-13883 Crossref PubMed Scopus (186) Google Scholar ] have demonstrated social learning that is sufficiently powerful to sustain different traditions.