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CURRENT ANTHROPOLOGY Volume 39, Number 5, December 1998@ 1998 by The Wenner-Gren Foundation for Anthropological Research. All rights reserved 001 r-3204/98/3905-0002$3.00

Chimpanzee andHuman Cultures

by Christophe Boesch andMichael Tomasello

Culture has traditionally been attributed only to human beings.Despite growing evidence of behavioral diversity in wild chim-panzee populations, most anthropologists and psychologists stilldeny culture to this animal species. We argue here that cultureis not monolithic but a set of processes. These processes showmuch diversity both in the social norms and models that deter-mine which individuals will be exposed to particular culturalvariants and what cultural variants will be present in the popula-tion and in the social learning mechanisms that determine thefidelity of transmission of the variants over time. Recognition ofthe diversity of these processes is important because it affectscultural dissemination, cultural evolution, and the complexity ofcultural artifacts. A comparison of chimpanzee and human cul-tures shows many deep similarities, thus suggesting that theyshare evolutionary roots. Two possible differences between thetwo species are discussed. First, thanks to indirect means oftransmission such as language, cultural dissemination is possibleover greater stretches of time and space in humans than in chim-panzees. Second, human cultures rely more intensively thanchimpanzee cultures on cumulative cultural evolution throughthe ratchet effect, which allows the accumulation of modifica-tions over time and produces more elaborate cultural artifacts.

CHRISTOPHE BOESCH is Director of the Max Planck Institute forEvolutionary Anthropology (Inselstrasse 22-26, 04103 Leipzig,Germany). Born in 1951, he was educated at the University ofGeneva (Diplom, 1975) and the University of ZUrich (Ph;D.,1984). He has been director of the Tai chimpanzee project since1979. His publications include "Cooperative Hunting in WildChimpanzees" (Animal Behaviour 48:653-87), "Innovation inWild Chimpanzees" (International Journal of Primatology 16:1-16), and "The Emergence of Cultures among Wild Chimpan-zees," in Evolution of Social Behaviour Patterns in Primates andMan, edited by W. G. Runciman, J. Maynard-Smith, and R. I. M.Dunbar (Oxford: Oxford University Press for the British Acad-emy, 1996).

MICHAEL TOMASELLO is Co-director of the Max Planck Institutefor Evolutionary Anthropology in Leipzig. He was born in 1950and received his B.A. from Duke University in 1972 and hisph.D. from the University of Georgia in 1980. Among his publi-cations are (with A. Kruger and H. Ratner), "Cultural Learning"(Behavioral and Brain Sciences 16:495-5U) and (with J. Call)"The Social Cognition of Monkeys and Apes" (Yearbook of Physi-cal Anthropology 37:273-305) and Primate Cognition (Oxford:Oxford University Press, 1997).

The present paper was submitted 19 x 97 and accepted 26 XI 97;the final version reached the Editor's office 17 XII 97.

There is little agreement among anthropologists on pre-cisely what is meant by the term "culture" as it is ap-plied to human social groups (e.g., Kroeber and Kluck-hohn 1952, Shore 1996). It might be supposed thatlooking to nonhuman primate societies for the evolu-tionary roots of human culture would simplify thedefinitional problems involved, if only because primatesocieties are not expected to include such ideal entitiesas values, attitudes, and beliefs, whose role in culturehas been the main point of contention in many anthro-pological debates. Unfortunately, this is not the case,even though evolutionary biologists and comparativepsychologists interested in culture have been primarilyconcerned with seemingly straightforward processes ofsocial learning and other forms of nongenetic informa-tion transfer among members of social groups. Themain problem is that the different disciplines involvedapproach the problem of culture with different sets ofconcerns. The basic dichotomy is between biologicalapproaches, in which all information that is transmit-ted nongenetically among members of a group is of in-terest (e.g., Bonner 1980, Boyd and Richerson 1985,Dawkins 1976, Cavalli-Sforza and Feldman 1983, Mun-dinger 1980), and more psychological approaches, inwhich the main concern is the cognitive and learningmechanisms by means of which such information istransmitted (e.g., Galef 1992, 1996; Tomasello 1990,1996).

These two approaches may be illustrated with thewell-known case of the potato washing of a group of Jap-anese macaques (Kawamura 1959, Kawai 1965). Ayoung female of this species discovered a new and use-ful food-processing technique with human-provisionedpotatoes that had become sandy, and this behaviorspread quickly-at least in the context of evolutionarytime-to other group members, possibly as they imi-tated one another's behavior. The researchers docu-mented in meticulous detail which individuals ac-quired the behavior and when they acquired it,establishing, among other things, that (1) the relativesand close associates of the original inventor acquiredthe new behavior first and (2) adult males generally didnot acquire the new behavior at all. From a biologicalpoint of view, an acquired skill-and one that wouldseem to be at least somewhat instrumentally useful-was transmitted among individuals of a group and con-tributed to improved methods of foraging. On the basisof the general similarity of this process to human cul-tural transmission, Japanese macaque potato washinghas been taken as a textbook case of cultural transmis-sion that illustrates the deep evolutionary roots of hu-man culture.

Recent reanalysis and reinterpretation of these obser-vations from a more psychological perspective, how-ever, have also highlighted some possible differences ofthis case from the human case. Galef (1992) reanalyzedthe original data and suggested that individual Japanesemacaques most likely learned to wash potatoes on theirown (as had the original inventor), not by imitatingtheir groupmates. As evidence for this view he noted

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seen a change of state effected, the observer knowsmore about the physical nature of an object: that nutscrack, that rocks are heavy and hard, that fruit pedun-cles are flimsy.

3. Learning relationships among objects. Having seenan object manipulated, the observer knows more aboutthe structural relationships that make it up or intowhich it meshes: that nuts are hollow and contain food,that rocks can cover food, that lids are threaded.

4. Learning what can be done with an object. Havingseen an object used in a particular way, the observerknows that this functional use is possible for this sortof object: a stick can be used as a rake, the lid of a jarcan be unscrewed, nuts can be smashed by strikingthem with rocks, a rod can be slid through a hole, fruitcan be knocked down by swiping at it with sticks.

This last would seem to be what Tomasello (1990) in-tended; certainly, if a chimpanzee could learn tool func-tion by observation, it would account for the results ofTomasello et a1. (1987), and his more recent definitionsmention "dynamic affordances." The trouble is thatthis is intrinsically about doing something with an ob-ject: raking, screwing, striking, swiping, sliding, etc.These are actions, and therefore emulation learning ofthis sort means associating a particular action with anobject. For some this simply is imitation (e.g., Heyes1994). In any case, this phenomenon is going to be hardto distinguish from imitation, and indeed the data To-masello et a1. (1987) describe as emulation have beensuggested instead to show imitation of one act from asequence (Whiten and Ham 1992) or imitation at an in-appropriately general level of hierarchical organization(Byrne and Russon n.d.). There is no fully convincingevidence yet that chimpanzees can learn by observationwhat actions can be performed with an object (rela-tional emulation) instead of how to perform them (imi-tation).

The two other senses of emulation learning-obser-vationallearning of physical properties and of relation-ships-are worth further investigation. In these cases,it should prove possible experimentally to divorce thecrucial revelations from the actions that typically pro-duce them. Problems may arise in distinguishing rela-tionship learning from much simpler, associative expla-nations: for instance, linking the taste of nut meat withthe sight of the unopened nut rather than appreciatingnotions of containment and hollowness. However, themore elaborated representations should generalize toother tasks involving containment and hollowness,whereas associative linking would remain specific tonut cracking.

The challenge is worth some effort, for it is about un-derstanding not merely how animals learn to deal withphysical problems but how they understand and repre-sent the world. Is this a matter of relational operatorslike "under," "inside," and "through," material descrip-tors like "brittle," "tough," "heavy," "flimsy," or justan undifferentiated mass of associations as animal-learning theorists would suppose?

BENNETT G. GALEF JR.Department of Psychology, McMaster University,Hamilton, Ont., Canada L8S 4KI. 30 III 98

The authors of this article are to be congratulated forproviding both a comprehensive account of current evi-dence of tradition in chimpanzees and a useful frame-work for comparing traditions in humans and apes. Iam, however, concerned that the article does not ad-dress some fundamental conceptual and evidentialproblems in the search for "the evolutionary roots ofhuman culture." Three such problems (discussed ingreater detail in Galef 1992) are as follows:

I. Is culture a trait open to selection and consequentevolution? Culture is not a characteristic of individuals,and therefore culture per se cannot, in the biologicalsense, evolve. Individuals may have cognitive processesenabling them to develop traditions; such cognitive pro-cesses are characteristics of individuals, open to selec-tion and to elaboration by evolution, and possibly in-crease the ability of individuals to acquire socially andtransmit patterns of behavior. However, evolution ofcognitive processes supporting culture is not at all thesame thing as evolution of culture itself.

2. AIe the "cultures" of chimpanzees and humans ho-mologous? If culture is not an evolving characteristic ofpopulations and increasing complexity in culture re-flects the evolution of cognitive processes underlyingthe ability to acquire socially and transmit behavior,then only those chimpanzee traditions that expresssocial-learning processes homologous to those that sup-port human culture should be discussed as possible an-tecedents of human culture. It follows that unless onebelieves, for example, that local enhancement some-how evolved into active teaching, language, imitation,or some other process important in the maintenance ofhuman culture, chimpanzee traditions resulting fromlocal enhancement are not relevant to discussion of theroots of human culture.

Unfortunately, in free-living chimpanzees, traditionsthat reflect cognitive processes such as imitation andactive teaching are difficult to discriminate from tradi-tions resting on cognitive processes such as local en-hancement that are not true antecedents of human cul-ture.

3. If chimpanzees have culture like that of humans,why is evidence of active teaching or imitation and ofratcheting so weak in wild chimpanzees? It-is generallyagreed that social transmission processes that simplycall the attention of an observer to aspects of the envi-ronment that others are exploiting (e.g., local enhance-ment, passive teaching, emulation) cannot provide a ba-sis for cumulative cultural change (ratcheting). Oncethese forms of social learning have focussed attentionon some aspect of the environment, individuals mustlearn for themselves how to manipulate that portion ofthe environment. No individual can copy behavioral in-novations of its predecessors, and, almost by definition,no cumulative cultural change can occur.

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The characteristic of human culture that makes it socentral to human life is its cumulative potential. Eachgeneration can inherit intact the innovations of preced-ing generations, improve upon that inheritance, andpass on improved behavioral variants. Over generations,patterns of behavior develop that no individual couldacquire as a result of his/her asocial interaction withthe physical environment.

While evidence of traditions in both free-living chim-panzees and other wild animals is overwhelming, evi-dence in any nonhuman species of free-living animal ofteaching, imitation, or cumulative culture is not strong.For example, Boesch, after ten years of field observation,reports two incidents that he interprets as instances ofactive teaching by chimpanzees. Others who havewatched wild chimpanzees for hundreds of man yearsreport active teaching by chimpanzees even less fre-quently than Boesch. If active teaching exists in chim-panzees and is adaptive, it is surprising that it is ex-pressed so rarely. Similar arguments can be made on thebasis of observed failures of chimpanzees (e.g., Goodall1986: 426; Kitahara-Frisch and Norikoshi 1982) or otherfree-living primates (see Tomasello and Call 1997: 282-84 for review) to imitate adaptive behaviors after watch-ing others repeatedly exhibit them.

We know of nothing that wild chimpanzees do thatan individual chimpanzee could not learn for itself(Goodall 1970). We can, therefore, tentatively concludethat in the millions of years that Pan troglodytes hasexisted, chimpanzees have not ratcheted any behaviorto a level where the cumulative effects of culture areobvious. By contrast, I suspect that one would not haveto observe even the most technologically or sociallyprimitive of human social groups for 30 hours, nevermind 30 years, to see examples of behavior that wereobviously the product of cumulative culture.

In summary, it is not my position that chimpanzeesdo not actively teach, imitate, or exhibit cumulativecultural change homologous to human culture. Perhapsthey do. However, "culture," like "adaptation," is anonerous concept (Williams 1966). T4e burden of prooflies with those who would argue for the existence ofhuman-like culture in any nonhuman species. I do notbelieve that proof has yet been provided.

TIM INGOLDDepartment of Social Anthropology, University ofManchester, Oxford Road, Manchester MI3 9PL,England (Tim.lngold@man.ac.uk). 30 IV 98

It is certainly true, as Boesch and Tomasello remark,that the several disciplines involved with the phenom-ena of culture approach them with very different con-cerns and that this puts formidable obstacles in the wayof interdisciplinary syntnesis. The basic dichotomy,they say, is between biological approaches, which fo-cus on culture as a corpus of information transmittedby other-than-genetic means, and psychological ap-proaches, which focus on the mechanisms of transmis-

sion themselves. There is no incompatibility here;rather, the two sets of approaches are perfectly comple-mentary. It stands to reason that if information is to betransmitted across the generations so as to form a cul-tural tradition, then mechanisms must be in place toenable such transmission to occur. Furthermore, thiscomplementarity of approach is underwritten by a com-plex of shared assumptions which are implicit in themetaphor of transmission, in the notion of "culturalvariants" as particles of transmissible information, andin the idea of behaviour as their observable expression.

These assumptions, however, which remain perva-sive in biological and psychological circles, have longsince been abandoned by the majority of social and cul-tural anthropologists-albeit with notable exceptions(Sperber 1996). Yet, paradoxically, in addressing thequintessentially anthropological "problem of culture,"Boesch and Tomasello completely bypass recent andcontemporary approaches in social and cultural anthro-pology. These approaches, admittedly, are many andvaried, as indeed are the approaches to be found in thecurrent literatures of biology and psychology. Fortu-nately, not all biologists are committed to a reduction-ist view of the organism as a vehicle for the propagationof form-and-behaviour-specifying information, nor areall psychologists committed to what could be called theXerox model of behaviour, according to which every ex-emplar of a traditional practice is run off from a mastercopy installed within the mind of the individual.

These, nevertheless, are the theoretical commit-ments that Boesch and Tomasello bring to their work.And if there is a fundamental and intractable dichot-omy, it is between the kind of approach they adopt,with its emphasis on the distribution and transmissionof information, and more developmentally and ecologi-cally oriented approaches in biology and psychology(e.g., Oyama 1985, Dent-Read and Zukow-Goldring1997) which ground the activities of organisms in an on-going and mutually constitutive engagement with theirenvironments. These latter approaches chime withmuch recent work in anthropology which has stressedthe inseparability of knowledge and practice and theembodied character of cultural skills (e.g., Bourdieu1990, Csordas 1990, Lave 1990, Lave and Wenger 1991).They also resonate with the position I have taken in myown work (Ingold 1996a, b).

In comparing the ways in which human beings andchimpanzees learn, the important thing, according toBoesch and Tomasello, is whether novices realise fromwatching others that a certain operation is possible butare left to their own devices to figure out how to do itor whether they precisely copy the bodily routines oftheir mentors so that the technique is literally repro-duced across generations. Depending on the answer,Boesch and Tomasello would describe the learning situ-ation as one of either emulation or imitation. For themthe distinction is absolutely critical, for only in the lat-ter case can one speak of the transmission of technique,and only if it is transmitted can the technique form partof a cultural tradition.