Culture extends the scope of evolutionary biology in the great apes

Abstract

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.

Keywords: chimpanzee; culture; evolutionary biology; orangutan; social learning.

Fig. 1.

Peering (39) by a juvenile orangutan as her mother extracts termites from dead wood. Image courtesy of Christiaan Conradie and Caroline Schuppli.

Fig. S1.

Investment in offspring competence. (Upper) A mother donates her tool to a begging offspring. (Lower) The offspring has begun to termite-fish. Following the tool transfer, the termite-gathering efficiency of the tool donor is depressed, as illustrated by the mother’s selecting a replacement tool in the second frame. Still frames reused with permission from ref. and thanks to Stephanie Musgrave, Crickette Sanz, Dave Morgan, and Goualougo Triangle Ape Project.

Fig. 2.

Convergent evidence for a culture of nut-cracking in chimpanzees. Evidence for nut-cracking is seen at multiple sites in West Africa (20, 21, 60) (white stars) but is absent at others (black stars). The gray star indicates an early report in Cameroon, which was not subsequently confirmed. Independent studies confirmed availability of raw materials at two such sites (61, 62). Experiments showed East African chimpanzees (two-letter ID codes) did not initially nut-crack (Phase 1), but when half of the population was exposed to a proficient model, they began to do so (Phase 2), and all did so once exposed (Phase 3) (31, 32).

Fig. S2.

Three young chimpanzees, A, B, and C, were exposed to two initially alarming objects, a swing and a satellite (moving ball). Every 2 mo, one of the three chimpanzees was replaced by a naive one, as indicated in the sequence BCD, CDE, and so on. Adaptive bolder approaches were socially inherited and over time came to dominate, resulting in a culture of common contact with the objects (86).

Fig. 3.

Helical curriculum model of skill development (after ref. 32). Over repeated cycles of observation-of-expert and practice, the social learner is able to assimilate more information from the expert and gradually improve his/her skill level. See the text for more explanation.