This mode of inquiry is expanding rapidly, so Andrew Whiten’s review of what an “extremely broad array of observational and experimental methodologies has taught us about the cultural lives of chimpanzees, gorillas, and orangutans” is timely and insightful. This article is striking for what it takes for granted—“culture permeates the lives of the great apes in the breadth of behavioral repertoires affected and also in their time-depth”—and for its mission, which is to test whether a statement about whales—“culture . . . is a major part of what whales are”—is also valid for great apes. No suspense, the answer is yes; what’s interesting is how well-substantiated this case is.
Research on social learning in apes extends back over a century and builds from a basic experimental model to see whether a naïve subject acquires a skill through observation, either by copying actions or emulating movements. This approach shifts into a cultural frame when it probes to see whether this learning passes from the learner to other subsequent learners, persisting across time or generations. Nut-cracking techniques using natural hammer materials pass along chains of direct social associations but also diffuse through groups, in the wild and in captivity. Over the last three decades, systematic observations in the field further expand the cultural frame by examining a range of behaviors, from foraging to nest-building. This work generated lists of cultural activities—over 30 forms of tool use for chimpanzees were established by 2001; the orangutan list of 2003 included a dozen different forms of tool use that went beyond food extraction to encompass forms of hygiene and building comfort (leaf-cushions); the gorilla list was just recently compiled (2016) and features activities such as cleaning fruit or building bridges across water, along with various forms of social play. The temporal depth of generational transmission is now being explored by via archaeology; a study in the Tai Forest of Ivory Coast uncovered over 4,000 years of nut-cracking remains, though this cultural activity may be much older.
The importance of culture for these genera of primates is evident in the amount of knowledge required for daily life: “large diet-sets need to be mastered and selected from the even more vast options a tropical forest offers. This mastery includes avoiding the numerous plant parts that are toxic, selecting relatively nutritious options, and avoiding relatively poor ones. Chimpanzees may eat more than 300 different food types (species × parts) in a year.” This involves “years of close apprenticeship to a mother who daily displays her knowledge of such a large but selective diet-set,” modeling an adaptive response to this challenging complexity. But their cultural activities run through a gamut of social interactions, from building and maintaining social bonds through local grooming customs through performing distinctive hygienic rituals or pursuing certain courtship gambits. The role of culture is evident in all of these social activities. The speculative question is how these diverse evidentiary and observational strands play into a case for revising evolutionary theory: do these cultural repertoires suggest “new form of evolution based not on genetic but on social inheritance?” We see this with humans, but “How does ape culture compare?”
Whiten systematically frames this question via eight evolutionary principles derived from Darwin. Starting with the core trinity (variation, selection, and inheritance), the evidence is strong for transmission via social learning, but “as yet there seems to be little direct recording of cultural evolutionary change through competition and selection within this variation.” Experimental designs to test cultural transmission might yet fill this gap, Whiten suggest. With the rest—adaptation, accumulation of modification, convergent evolution, geographic variation, and change of function—the case is more tenuous. Examples are emerging from the wild: “Chimpanzees in Bossou, Guinea, were shown to be reliant on two forms of technology, in particular nutcracking and pestle-pounding (a means of extracting nutritious pulp from the apex of palm trees) during the dry season when fruit became scarce; these cultural variants allow these apes to inhabit otherwise inadequate habitats.” Such adaptations can be social, as well: “In a community of chimpanzees that customarily practices hand-clasp grooming, it may be adaptive to learn this behavior from those already using it; and where a particular courtship gambit such as leaf-clipping has become common, it will likely be beneficial to adopt this behavior as an action already recognized by one’s potential mating partner.” I won’t detail his considerations of each of the subsequent evolutionary principles, the gist of which is that culture may evolve as species do; this is a matter for another post. Whiten is making a case for thinking somewhat differently about biology: “cultural transmission by social learning also extends the scope of biological systems by incorporating additional dimensions of inheritance and evolution.” Rather than being opposed to the biological or freed from evolution, “culture extends biology insofar as some culturally transmitted behaviors are evolutionarily consequential.” Here Whiten cycles back to the cetaceans; there’s not much evidence among the great apes, yet, of “dramatically different specialisms such as seen in killer whales.” But questions around “cultural intelligence” and the rise of social cognition are intriguing. Which comes first, bigger brains or bigger social groups? Gorillas and orangutans complicate the base assumptions behind either argument.
Andrew Whiten, “Culture Extends the Scope of Evolutionary Biology in the Great Apes,” PNAS 114, no. 30: 7790–97, https://doi.org/10.1073/pnas.1620733114.
Discoveries about the cultures and cultural capacities of the great apes have played a leading role in the recognition emerging in recent decades that cultural inheritance can be a significant factor in the lives not only of humans but also of nonhuman animals. This prominence derives in part from these primates being those with whom we share the most recent common ancestry, thus offering clues to the origins of our own thoroughgoing reliance on cumulative cultural achievements. In addition, the intense research focus on these species has spawned an unprecedented diversity of complementary methodological approaches, the results of which suggest that cultural phenomena pervade the lives of these apes, with potentially major implications for their broader evolutionary biology. Here I review what this extremely broad array of observational and experimental methodologies has taught us about the cultural lives of chimpanzees, gorillas, and orangutans and consider the ways in which this knowledge extends our wider understanding of primate biology and the processes of adaptation and evolution that shape it. I address these issues first by evaluating the extent to which the results of cultural inheritance echo a suite of core principles that underlie organic Darwinian evolution but also extend them in new ways and then by assessing the principal causal interactions between the primary, genetically based organic processes of evolution and the secondary system of cultural inheritance that is based on social learning from others.
Hartigan, John. “How to Study Culture in Nonhumans.” August 8, 2017. Commentary to Social Theory for Nonhumans. Manifold ed. Minneapolis: University of Minnesota Press, forthcoming. https://doi.org/10.5749/9781452958446.