Tatyana Humle

Emergence of Culture in Wild Chimpanzees: Education by Master-Apprenticeship

This chapter describes a series of field experiments aimed at investigating aspects of emergence of cultural traditions in wild chimpanzee communities. Long-term research at a number of sites in Africa has revealed that each community of chimpanzees has developed its unique set of cultural traditions (Boesch and Boesch-Achermann 2000; Goodall 1986; McGrew 1992; Nishida 1990; Whiten et al. 1999). The evidence poses an intriguing question: How did these unique cultures come into existence?.

Chimpanzees’ flexible targeted helping based on an understanding of conspecifics’ goals

Humans extensively help others altruistically, which plays an important role in maintaining cooperative societies. Although some nonhuman animals are also capable of helping others altruistically, humans are considered unique in our voluntary helping and our variety of helping behaviors. Many still believe that this is because only humans can understand others’ goals due to our unique “theory of mind” abilities, especially shared intentionality. However, we know little of the cognitive mechanisms underlying helping in nonhuman animals, especially if and how they understand others’ goals. The present study provides the empirical evidence for flexible targeted helping depending on conspecifics’ needs in chimpanzees. The subjects of this study selected an appropriate tool from a random set of seven objects to transfer to a conspecific partner confronted with differing tool-use situations, indicating that they understood what their partner needed. This targeted helping, (i.e., selecting the appropriate tool to transfer), was observed only when the helpers could visually assess their partners situation. If visual access was obstructed, the chimpanzees still tried to help their partner upon request, but failed to select and donate the appropriate tool needed by their partner. These results suggest that the limitation in chimpanzees’ voluntary helping is not necessarily due to failure in understanding others’ goals. Chimpanzees can understand conspecifics’ goals and demonstrate cognitively advanced targeted helping as long as they are able to visually evaluate their conspecifics’ predicament. However, they will seldom help others without direct request for help.

Chimpanzees share forbidden fruit.

The sharing of wild plant foods is infrequent in chimpanzees, but in chimpanzee communities that engage in hunting, meat is frequently used as a ‘social tool’ for nurturing alliances and social bonds. Here we report the only recorded example of regular sharing of plant foods by unrelated, non-provisioned wild chimpanzees, and the contexts in which these sharing behaviours occur. From direct observations, adult chimpanzees at Bossou (Republic of Guinea, West Africa) very rarely transferred wild plant foods. In contrast, they shared cultivated plant foods much more frequently (58 out of 59 food sharing events). Sharing primarily consists of adult males allowing reproductively cycling females to take food that they possess. We propose that hypotheses focussing on ‘food-for-sex and -grooming’ and ‘showing-off’ strategies plausibly account for observed sharing behaviours. A changing human-dominated landscape presents chimpanzees with fresh challenges, and our observations suggest that crop-raiding provides adult male chimpanzees at Bossou with highly desirable food commodities that may be traded for other currencies.

The Chimpanzees of Bossou and Nimba

In southeastern Guinea, on the border of Liberia and the Ivory Coast, some 2,500 humans live as close neighbors to a group of chimpanzees named for the village that the two species share: Bossou. In the 1960s, the pioneering Adriaan Kortlandt tested the reaction of the chimpanzees to encountering a stuffed leopard, but it was in 1976 that the major scientific importance of the Bossou population began to be realized when Yukimaru Sugiyama launched a systematic observation of their ecology and behavior. Sugiyama was soon joined by others including Tetsuro Matsuzawa (1986) and Tatyana Humle (1995). Research on this population has been year-round since the 1990s. International and multifaceted, it includes a substantial amount of non-invasive experimentation and a large commitment to conservation management. The objects of this intense research activity are a community that was never counted at more than 23 and is now a mere 13. But if the Bossou population is tiny, its story is fascinating. The Bossou chimpanzees occupy 6 km 2 of sacred forest and farm bush almost a day’s journey from any others of their species, and in apparent response to their strange isolation they challenge various demographic and behavioral generalizations. Compared to other wild chimpanzees they reproduce fast and early (average first birth at 10.6 years), and there are hints of male transfer: 6 adolescent males have disappeared (as if by emigration) and 2 adult males immigrated separately for a few months each. Curiously no females have immigrated, so for a 27year period up to 2003, most of the breeding was by the same 7 adult females. But despite (or maybe because of?) its cultural inbreeding, this little group has developed a particularly rich set of socially learned traditions, and it is those that are the focus of more than half the 40 chapters of The Chimpanzees of Bossou and Nimba. Much of this material has been published elsewhere, but Matsuzawa, Humle and Sugiyama have made a major contribution by assembling 29 authors in an integrated and wide-ranging account of the culture and behavior of Bossou chimpanzees. While traditions such as pestlepounding, algae-scooping and arboreal ant-dipping get individual chapters, nut-smashing has such great ecological and evolutionary significance that the editors award it a kaleidoscope of perspectives including detailed biogeographies, experimental work in captivity, rich observational detail, field experiments and much cognitive analysis. Given that a plausible model of hominin origins involves a small population evolving by allopatric speciation from a chimpanzee-like ancestor, this rich and well-rounded account should be equally appreciated by primatologists and anthropologists. The editors deserve congratulations for two special contributions that complement this satisfyingly balanced and integrated book. First, The Chimpanzees of Bossou and Nimba comes with a video offering hours of high-class viewing. Its 7 sections include not just the details of tool-using at Bossou but a vivid portrayal of social life. For teachers, these superb clips go a long way towards justifying the horrendous price of the book. Published online: March 13, 2012

Laterality in hand use across four tool-use behaviors among the wild chimpanzees of Bossou, Guinea, West Africa.

Population‐level right handedness is a human universal, whose evolutionary origins are the source of considerable empirical and theoretical debate. Although our closest neighbor, the chimpanzee, shows some evidence for population‐level handedness in captivity, there is little evidence from the wild. Tool‐use measures of hand use in chimpanzees have yielded a great deal of variation in directionality and strength in hand preference, which still remains largely unexplored and unexplained. Data on five measures of hand use across four tool‐use skills—ant‐dipping, algae‐scooping, pestle‐pounding and nut‐cracking—among the wild chimpanzees of Bossou, Guinea, West Africa, are presented here. This study aims to explore age‐ and sex‐class effects, as well as the influence of task motor, cognitive and haptic demands, on the strength and directionality of hand preference within and across all five measures of hand use. Although there was no age‐ or sex‐class effect on the directionality of hand preference, immature ≤10 years old tended to be less lateralized than adults, especially adult females. Nut‐cracking, the most cognitively complex of the four behaviors and the only one requiring complementary coordination of both hands, yielded the greatest strength in hand use with all adults expressing exclusive use of one hand over the other, without overall significant directional preference. The least lateralized behavior was pestle‐pounding, which required bimanual coordination, but also imposed constraints owing to fatigue. It emerged that only the most hazardous tool use, i.e. ant‐dipping, and the sole haptic task, i.e. the extraction by hand of crushed oil‐palm heart, were laterally biased and both to the right. Shared motor or grip patterns in tool‐use skills failed to reveal any specialization in hand use at the individual level. Finally, Bossou chimpanzees demonstrated a tendency for a population‐level right‐hand use. Am. J. Primatol. 71:40–48, 2009.

Cultural differences in army ant predation by West African chimpanzees? A comparative study of microecological variables

Behavioural diversity in the predation pattern of army ants (Dorylus spp.) by different populations of wild chimpanzees, Pan troglodytes, has been proposed to reflect different cultural traditions. Chimpanzees use either stick tools (known as ant dipping) or simply their hands to prey on two groups of army ants (epigaeic and intermediate species). A recent analysis has shown that, contrary to the cultural hypothesis, the tool length and associated harvesting technique used by chimpanzees in different populations is to a large extent influenced by characteristics of the ants themselves. However, in line with the cultural

Behavioural Diversity among the Wild Chimpanzee Populations of Bossou and Neighbouring Areas, Guinea and Côte d’Ivoire, West Africa

We present a preliminary report on the differences and similarities in material culture among four neighbouring chimpanzee (Pan troglodytes verus) communities. One of these communities includes Bossou, a long-term field site of wild chimpanzees, in Guinea, West Africa. We also conducted surveys of three new sites. Two of those surveyed areas, Seringbara in Guinea and Yealé in Côte d’Ivoire, are located less than 12 km away from Bossou in the Nimba Mountains region, which forms a natural boundary between Guinea and Côte d’Ivoire. The third, Diécké, is situated further south-west, closer to the border with Liberia. During the surveys, we gathered behavioural information about these neighbouring populations of chimpanzees. The differences, as well as similarities, in material culture were tabulated based on our findings. The three behavioural variants found so far involve differences in nut cracking behaviour with regard to the species of nut cracked. Some variation in materials used for nut cracking has also been recorded. However, we still need to establish whether these local variations can be explained by the demands of the physical and biotic environments in which the populations of chimpanzees live. If these alternative hypotheses can be excluded with continuing research at the study sites, these differences are likely to be cultural behaviours that are influenced by the social context and mode, i.e. horizontal, vertical or oblique, of transmission, by the social structure and organisation of each community and/or perhaps by some form of social norms prevalent within these communities.

The fourth dimension of tool use: temporally enduring artefacts aid primates learning to use tools

All investigated cases of habitual tool use in wild chimpanzees and capuchin monkeys include youngsters encountering durable artefacts, most often in a supportive social context. We propose that enduring artefacts associated with tool use, such as previously used tools, partly processed food items and residual material from previous activity, aid non-human primates to learn to use tools, and to develop expertise in their use, thus contributing to traditional technologies in non-humans. Therefore, social contributions to tool use can be considered as situated in the three dimensions of Euclidean space, and in the fourth dimension of time. This notion expands the contribution of social context to learning a skill beyond the immediate presence of a model nearby. We provide examples supporting this hypothesis from wild bearded capuchin monkeys and chimpanzees, and suggest avenues for future research.

Invention and modification of a new tool use behavior: Ant-fishing in trees by a wild chimpanzee (Pan troglodytes verus) at Bossou, Guinea

Wild chimpanzees are known to have a different repertoire of tool use unique to each community. For example, “ant‐dipping” is a tool use behavior known in several chimpanzee communities across Africa targeted at driver ants (Dorylus spp.) on the ground, whereas “ant‐fishing,” which is aimed at carpenter ants (Camponotus spp.) in trees, has primarily been observed among the chimpanzees of Mahale in Tanzania. Although the evidence for differences between field sites is accumulating, we have little knowledge on how these tool use behaviors appear at each site and on how these are modified over time. This study reports two“ant‐fishing” sessions which occurred 2 years apart by a young male chimpanzee at Bossou, Guinea. Ant‐fishing had never been observed before in this community over the past 27 years. During the first session, at the age of 5, he employed wands of similar length when ant‐fishing in trees to those used for ant‐dipping on the ground, which is a customary tool use behavior of this community. Two years later, at the age of 7, his tools for ant‐fishing were shorter and more suitable for capturing carpenter ants. This observation is a rare example of innovation in the wild and does provide insights into problem‐solving and learning processes in chimpanzees. Am. J. Primatol. 70:699–702, 2008.

Polymorphism of the Tryptophan Hydroxylase 2 (TPH2) Gene Is Associated with Chimpanzee Neuroticism

In the brain, serotonin production is controlled by tryptophan hydroxylase 2 (TPH2), a genotype. Previous studies found that mutations on the TPH2 locus in humans were associated with depression and studies of mice and studies of rhesus macaques have shown that the TPH2 locus was involved with aggressive behavior. We previously reported a functional single nucleotide polymorphism (SNP) in the form of an amino acid substitution, Q468R, in the chimpanzee TPH2 gene coding region. In the present study we tested whether this SNP was associated with neuroticism in captive and wild-born chimpanzees living in Japan and Guinea, respectively. Even after correcting for multiple tests (Bonferroni p = 0.05/6 = 0.008), Q468R was significantly related to higher neuroticism (β = 0.372, p = 0.005). This study is the first to identify a genotype linked to a personality trait in chimpanzees. In light of the prior studies on humans, mice, and rhesus macaques, these findings suggest that the relationship between neuroticism and TPH2 has deep phylogenetic roots.