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The roots of primate predatory behavior
M. D. Rose Section of Gross Anatomy, Department of Surgery, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06510, U.S.A.
Received 3 May 1977 and accepted 15 July 1977 Keywords : subsistence patterns, predation, human evolution, Papio, Cercopitheeusaethiops, Pan troglodytes.
The Roots of P r i m a t e Predatory Behavior Evidence is examined that supports the view that in collectingpredatory primates many of the behaviours associated with the predatory component of the subsistence pattern are similar to those occurring during omnivorous collecting activities. General similarities are found between some elements of predatory behavior and some overall features of omnivorous foraging and feeding, and more specific similarities are found with collecting behavior directed towards rarely occurring, clumped, or highly favoured plant foods. It is suggested that there are few elements in primate predatory behavior that require more than the general behavioral plasticity and adaptability that omnivorous, ground foraging primates exhibit with respect to the exploitation of different types of plant foods. The emergence of the gathering-hunting human subsistence pattern out of a collecting-predatory pattern that was in turn based on omnivorous collecting is a model for an evolutionary pathway that is consistent with both direct and comparative evidence. While the comparative evidence enables some general features of this model to be described, caution is advised about applying more detailed features of the subsistence behavior of non-human mammals to the postulated subsistence patterns of hominid populations the morphology and behavior of which were not identical to those of living primate or other mammalian species.
1. I n t r o d u c t i o n T h e fossil a n d o t h e r d i r e c t evidence for the evolution o f h u m a n subsistence p a t t e r n s is p a t c h y a n d equivocal. I n t e r e s t in this aspect o f h u m a n e v o l u t i o n is c u r r e n t l y m a i n t a i n e d b y evidence o f three m a i n types in a d d i t i o n to the d i r e c t evidence. Studies o f c o n t e m p o r a r y h u m a n p o p u l a t i o n s i n d i c a t e t h a t the basic h u m a n subsistence p a t t e r n is b r o a d l y b a s e d (e.g. Lee, 1968, 1972; Lee & D e V o r e , 1968). T e l e k i (1975) suggests t h a t t h e t e r m g a t h e r i n g - h u n t i n g , r a t h e r t h a n h u n t i n g or h u n t i n g - g a t h e r i n g , best describes the p a t t e r n . A s e c o n d line o f evidence is used to p o i n t o u t parallels b e t w e e n the social o r g a n i z a t i o n a n d subsistence p a t t e r n s of some social carnivores a n d some features o f the basic h u m a n p a t t e r n (e.g. S c h a l l e r & L o w t h e r , 1969; K i n g , 1975, t 9 7 6 ; T h o m p s o n , 1975, 1976). T h e t h i r d line of a p p r o a c h seeks to relate h u m a n g a t h e r i n g - h u n t i n g p a t t e r n s to c o l l e c t i n g p r e d a t o r y p a t t e r n s o f n o n - h u m a n p r i m a t e s (e.g. Teleki, 1975; H a r d i n g , 1975). T h e attractiveness o f the t h i r d a p p r o a c h is t h a t it allows c o m p a r i s o n s to be m a d e b e t w e e n the t o t a l h u m a n subsistence p a t t e r n a n d those o f the n o n - h u m a n p r i m a t e s c o n c e r n e d . Differences b e t w e e n the p a t t e r n s c a n be seen to be o f d e g r e e r a t h e r t h a n k i n d (e.g. Teleki, 1975). Despite p o t e n t i a l a n d a c t u a l difficulties in using evidence from living n o n - h u m a n m a m m a l s , Schaller & L o w t h e r (1969) a n d K i n g (1975) suggest t h a t evidence o f the t h r e e types m a y all b e useful for ideas c o n c e r n i n g different phases of the evolution o f the h u m a n p a t t e r n . Teleki (1975) a n d K i n g (1975) b o t h suggest t h a t some of the e l e m e n t s o f the p r e d a t o r y c o m p o n e n t o f the c o l l e c t i n g - p r e d a t o r y p a t t e r n s of living p r i m a t e s m a y h a v e o r i g i n a t e d in o m n i v o r o u s collecting b e h a v i o r . E v i d e n c e from the b e h a v i o r o f nonh u m a n m a m m a l s is thus u s e d to g e n e r a t e hypotheses c o n c e r n i n g the evolution o f h u m a n subsistence p a t t e r n s in the b i g - g a m e h u n t i n g phase (social c a r n i v o r e models) a n d in a Journal of Human Evolution (1978) 7, 179-189
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pre big-game hunting, collecting-predatory phase (baboon and chimpanzee models). Given the possibility that human gathering-hunting behavior may have had its origin in a hominid collecting-predatory pattern, speculations concerning the origin of the collecting-predatory pattern in even earlier hominid or hominoid subsistence behavior becomes of interest. This paper examines in more detail the suggestions of especially Teleki (1975), that some elements of the predatory behavior of living collector-predators may have arisen out of omnivorous collecting behavior. The results of this examination are then discussed in relationship to the possible course of the evolution of human subsistence patterns. Evidence will be examined concerning general aspects of the subsistence patterns of omnivorous, more terrestrially based primates, but attention will also be paid to subsistence behaviors related to plant food types that (like some types of animal food) require specialized techniques of collection, are patchily distributed in space and time, may have specific valuable nutritional components, may require changes in normal ranging patterns for their harvesting, or are favoured food items. Personal observations have been made on a number of primate species, during several years' field work in East Africa. Observations particularly relevant to this paper were made on olive baboons (Papio anubis), and vervet monkeys (Cercopithecus aethiops) in various habitats in Uganda and Kenya. Feeding behavior related to special plant foods, particularly the prickly pear cactus (0puntia vulgaris), has mainly been observed during field studies of collecting-predatory olive baboons at Gilgil, Kenya, and of vervet monkeys at Naivasha, Kenya.
2. Predatory Behavior and O m n i v o r o u s Collecting Teleki (1975) divides the predatory behavior of chimpanzees into a number of stages involving, in sequence, the pursuit, capture and consumption of the prey animal. Baboon predatory behavior may also involve these stages (Harding, 1974; Harding & Strum, 1976; Hausfater, 1976). Teleki recognizes three alternative pursuit modes; seizure, chasing and stalking, and relates seizure to normal manipulatory behaviors occurring during omnivorous collection. While chasing as such rarely occurs during the collection of plant foods, both olive baboons and vervet monkeys chase after and seize flying insects, often running bipedally to do so. The stalking of larger animal prey might seem to be a behavior pattern specifically associated with this type of food item. However, stalking is a particular example of a general strategy of approach to all types of food object that maximizes the chance of obtaining the object, while as far as possible minimizing the effort involved and the danger risked by the animal concerned. The patterning of activities is similar regardless of food type, even if individual behavioral elements may differ. Parallels with predatory stalking become closer in activities such as the gathering of prickly pear fruit by vervet monkeys. The fruit themselves and the plant on which they grow are extremely spiney and the plants form complicated branching masses up to about three meters in height. Vervet monkeys at Naivasha spend considerable periods of time pacing around the base of these plants to locate a ripe fruit in an accessible position. They then pick their way with great care up through the plant, sometimes halting to get a visual fix on the chosen fruit before continuing up and through the plant. This sequence of behaviors shows just those elements of premeditation and decision making that Teleki (1975) associates with chimpanzee chasing and stalking, and which may also occur in baboon predatory behavior (Harding,
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1973a, 1974; Strum, 1975; Harding & Strum, 1976; Hausfater, 1976). This plasticity of behaviour is also seen in other aspects of the "stalking" of prickly pear fruit by vervet monkeys. During the collection of most commonly occurring food objects in aboveground settings, food that is inadvertently dropped is virtually never followed to the ground and retrieved. However, because the gathering of prickly pear fruit involves the delicate removal of the fruit from the stem by a careful, usually one-fingered levering movement, the fruit frequently drops to the ground when it separates. In this case the vervet will follow the ~?uit to the ground, using another carefully picked out pathway through the plant, search out the fruit on the ground, and then consumes it. While to the human observer this seems an obvious behaviour pattern to follow, it nevertheless represents a pattern that departs radically from those occurring during regular food gathering. Olive baboons also modify behavior patterns to fit exceptional circumstances. Crook & Aldrich-Blake (1968) describe a stroking technique used by some olive baboons to to detach prickly pear leaves. Olive babooons at Gilgil use a different technique involving a downward levering movement of one or two finger tips applied to the end of the leaf (Rose, 1977). In each case the baboons were faced with a challenging food acquisition problem, which they solved by drawing on their manual and mental skills. Different collection techniques may also be developed by different age classes of a population during such activities as rock-turning in order to collect hidden invertebrates (Rose, 1977). The techniques differ in these instances, but the abilities involved are the same, and it is abilities such as these that must be called into play when the more complex problems of acquiring mobile animal food objects arise. Another aspect of predatory behavior of both chimpanzees and olive baboons is that the chasing and stalking behaviours utilized involve a degree of persistence, in terms of time spent attempting to acquire a food object, and of the number of attempts made, that rarely occurs during normal types of foraging (Teleki, 1975; Harding & Strum, 1976). However, the behaviour of both olive baboons and vervet monkeys in acquiring prickly pear plant parts indicates that if the food object is prized highly enough animals will persist until they have achieved their ends. Olive baboons digging for underground plant parts, or searching for and extracting honeycomb show a similar persistence, as do chimpanzees gathering honey or bird eggs (Van Lawick Goodall, 1968). These instances of premeditation, decision-making and general behavioral plasticity are all examples of the sophisticated cognitive skills and the capacity for acquiring abstract general strategems and response rules that Warren (1974) suggests differentiate primates from other mammals. These abilities seem to be particularly well developed in those broad-niched primates characterized by Struhsaker (1976) as "opportunistic omnivores" and by Parker (1974) as "opportunists", and are exhibited in a number of contexts related to foraging. Thus Hall (1962) points out that chacma baboons (Papio ursinus) rapidly develop effective manipulatory and exploratory skills that can be successfully generalized to a wide variety of problems related to food. A number of studies on Japanese macaques (Macacafuscata) have provided a detailed analysis of how these skills can be developed in novel feeding situations (e.g. Yamada, 1957; Itani, 1958; Kawamura, 1959, 1965; Kawai, 1965; Frisch, 1968). Predation by olive baboons at least, sometimes involves individuals or groups of animals changing their normal ranging patterns in order to seek out or pursue prey animals (Harding, 1973a; Strum, 1975). Long or short term variations in normal ranging patterns
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may be associated with a wide variety of factors o f which changes in resource availability and distribution, and the presence of other (conspecific) animal groups are two examples (e.g. Casimir & Butenandt, 1973; Fossey, 1974; Struhsaker, 1974). The vervet monkeys at Naivasha suddenly and drastically changed their ranging pattern, coincidentally with the ripening of the fruit of a localized area of prickly pear plants. Perhaps of more direct relevance to predatory behavior are variations in the foraging behavior of an individual or age-sex class. Sex differences in foraging patterns, or in diet, or both occur in the Gilgil olive baboons (Rose, 1977) and in yellow baboons (Papio cynocephalus) at Amboseli, Kenya (Post, pets. comm.). A more idiosyncratic example involved an adult male vervet monkey at Naivasha, that would regularly range away from the rest of its troop in order to investigate outlying stands of prickly pear plants. Altmann & Altmann (1970) and Post (pers. comm.) have observed similar excursions being made by yellow baboons to feed on fever tree gum. These examples, together with most observations of predatory behavior, indicate that there are sex differences in some aspects of ranging and foraging behavior that, as Teleki (1975) points out, have some relevance to a discussion of the origin of the division of labor that may occur in human gathering-hunting subsistence patterns. Teleki (1973a,b, 1975) mentions that more than one animal may be involved in chimpanzee predatory episodes, often acting in co-operation with each other. Strum (1975) and Harding & Strum (1976) have documented the development of a less complex co-operative pattern of relay chasing, out of individual chasing of animal prey by olive baboons. Co-operative behavior of these types is not seen in other types of food acquisition. However, there are a number of situations related to foraging and feeding where behaviors showing similar features do occur. While aggressive behavior is relatively common at clumped or highly favoured food sources (e.g. Hall, 1965; Chalmers, 1968; Gautier-Hion, 1970; Harding, 1973b; Wrangham, 1974) there are many situations where the spacing, orientation and interactions of individuals represents a type of co-operation that allows them to feed at the same site without aggression breaking out (e.g.Ripley, 1970). One aspect of the co-operative predation of both chimpanzees and olive baboons is that it entails the direction of the activities of different animals towards, and their physical convergence on the same food source. There are some situations, especially involving highly prized plant food items, where similar behavior is seen. Thus the investigation of outlying prickly pear clumps by the adult male vervet monkey mentioned above sometimes resulted in a few other animals, usually juvenile males, leaving the troop and converging on the same food source from different directions. This convergence never led to co-operative food acquisition by these vervet monkeys. However, the unintentionally co-operative behavior of relay chasing and eventual capture of prey animals by the Gilgil baboons indicates that this type of convergence can form the basis for more useful predatory behaviors, whether they are intentional or not. A more sophisticated type of co-operation has been observed by Maples (1969) in olive baboons raiding maized fields. Three types of diversionary tactics, one of which involved coalitions of males, females, and infants, were used to allow other troop members, sometimes acting as separate but coordinated raiding parties, to get to the maize. Maples et al. (1976) suggest that these may not be intentionally diversionary tactics, but that they result from the social subgrouping of the troops concerned, and the particular distribution of natural and man-made habitats in which the troops are active. This makes these instances even more
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interesting in the present context, as it shows the extent to which normal features of a species' life can combine to bring about what is in effect a new type of behavior. Teleki (1975) defines a stage of capture following a successful predatory pursuit by chimpanzees, which involves a succession of behaviors by which the prey is caught, killed and initially divided. The lunging and grasping movements associated with catching also occur during omnivorous collecting. Similarly the killing of prey animals, which either occurs incidentally as the animal is eaten to death, or as a result of neck biting or twisting, contains few elements that are not involved in the consumption of the tougher types of plant food. The specialized technique by which chimpanzees beat an animal to death by flailing it against a solid surface also involves behaviors normally used in feeding, aggression and display (Van Lawick Goodall, 1968, 197 I). Teleki (1975) points out that as in human hunting, there may be a stage in chimpanzee predation between the acquisition of a prey item and its consumption, during which the food is transported away from the kill site. Ground living primates sometimes transport plant foods, particularly in situations where animals are crowded at a rarely occurring or highly favoured food source. By removing itself and its food from the acquisition site the animal minimizes its chances of becoming involved in aggressive interactions and of having its food appropriated. In cercopithecines the food is usually carried in the mouth. Vervet monkeys at Naivasha and olive baboons at Gilgil transport prickly pear plant parts in this way, and these species have been observed transporting mushrooms, berry bearing twigs, and larger fruit at a number of sites. Other objects, ranging from infants to tools, are also transported by some primates in a variety of situations. Transporting behavior is thus a part of the behavioral repertoire of a number of primate species, and its specific association with predatory or hunting behavior again represents no more than the application of an existing ability in a new situation. T h e final stages of predatory episodes involve the dismantling and distribution of the prey item for consumption. Both chimpanzee and baboon groups sometimes share meat at this stage. Chimpanzees have also been observed sharing plant foods (Sugiyama, 1969; Hladik, 1973; McGrew, 1975). McGrew suggests that the sharing of meat may represent a more recent and specialized evolutionary development in chimpanzees, based on the phylogenetically more primitive pattern of plant food sharing. While the pattern of meat sharing in chimpanzees involves exceedingly complex interactions, Teleki (1975) has stressed that this distribution is along lines determined more by special dyadic relationships rather than by special rank (confirming the conclusions of Yerkes & Yerkes (1935) based on the observation of captive chimpanzees). Hladik (1973) and Savage, quoted in McGrew (1975) suggest that the mother-infant dyad may have special importance, which supports Van Lawick Goodall's (1968) suggestion that the begging gestures associated with food sharing, together with similar gestures associated with submission, reassurance , or grooming interactions, may all be related to gestures originally occurring in m o t h e r infant interactions. Kawabe (1966) provides evidence from a single predatory episode that rank behavior may in fact break down at a kill site, and suggests that this in itself m a y be a pre-adaptation to sharing. While meat distribution among baboons is less complex than in chimpanzees, Hausfater (1976) points out that it may be just as extensive. This distribution is made possible by a variety of factors, ranging from behaviors such as the "vulture response" (Altmann & A]tmann, 1970; Harding, 1973a, 1975) of baboons converging on a kill site (sometimes occurring with plant foods, as described above), to social factors such as mother-infant,
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infant-adult male, consort, play group or other relationship (Strum, 1975; H a r d i n g & Strum, 1976). T h e Gilgil olive baboons, and the Naivasha vervets both show sharing-like behaviors involving animals feeding from the same object or portions thereof, either in the context of the mother-infant dyad, by aggressive displacement, or by the retrieval of food dropped by another animal. T h e foods involved include mushrooms, some fleshy fruits, and prickly pear fruit a n d leaves. Thus while the fully developed patterns of food sharing of the h u m a n type m a y be rare a m o n g primates, even during predatory episodes, there does seem to exist a n u m b e r of behaviors and social relationships that can serve as a basis for the development of such patterns. 3. D i s c u s s i o n
The evidence examined above supports Teleki's (1975) suggestion that in some primate species there is a repertoire of maintenance and social behaviors that is utilizable, with or without some modification, in predatory situations. The precursors of predatory behavior seem to be most evident among the more terrestrial primates, living in open habitats, and with a relatively broad subsistence base associated with an extensive repertoire of collecting behaviors. These facts are relevant to a consideration of the evolutionary development of h u m a n subsistence behavior. There is an almost unavoidable bias to thinking about this subject. As with other "unique" and important h u m a n characteristics, such as language, tool use, and striding bipedalism there is a double temptation, to either minimize the relevance of these characteristics to the h u m a n condition when they occur in a m u t e d or differently developed form in other species or, if their relevance is admitted, to attribute the same aura of specialness to them as is associated with their expression in humans. I t is the latter temptation that is perhaps the stronger with repect to thinking about the hunting component of h u m a n subsistence patterns and the predatory component of non-human primate collecting-predatory subsistence patterns. Whether or not h u m a n subsistence patterns are considered to be unique, the gathering and hunting components of the gathering-hunting pattern involve different behavioral elements that bear little obvious relationship to each other. I n addition, the hunting component would seem to require a n u m b e r of specialized behaviors. However, speculations concerning the development of these behaviors might be more profitable if, instead of projecting concepts of uniqueness backward in time, emphasis is placed on the possible development of new patterns out of more recognizably '"ordinary" components. One likely place to seek for these components in the case of hunting behavior is in predatory behavior similar to that exhibited by some living primate species. Predatory behaviour involving larger animal prey would not seem to be of more than marginal importance in populations at large of non-human primates, but because of its relevance to h u m a n hunting behavior, it has received a great deal of attention when it does occur. This tendency is not helped by the fact that in at least one population, predatory behavior has been seen to develop very rapidly. However, this very fact should serve to indicate that what is occurring is not necessarily arising de novo but m a y be a new expression of existing behaviors of the individuals and populations concerned. , J u s t as h u m a n hunting is p a r t of a broader gathering-hunting pattern, so too is predatory behavior part of a much broader collecting-predatory pattern, but whereas in the h u m a n pattern the gathering and hunting components are clearly differentiated, there are obvious links between the limited predatory component and the more extensive
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collecting component of the collecting predatory pattern. As far as the human observer is concerned this predatory behavior may seem special, but as far as the animals involved are concerned larger animal prey may be just another food source, to be exploited by using the behaviours available for the exploitation of other food sources. These behaviors may well need to be modified in predation, but so may they for the exploitation of other food types. One of the few points of agreement concerning hominid evolution is that its early stages were associated with a shift to a more terrestrially based existence in more open habitats and with a change in, if not a broadening of the subsistence base. Given that such a shift took place, and that a gathering-hunting subsistence pattern was developed in at least some species of later hominids, it is consistent with the comparative evidence to suppose that early hominids possessed a repertoire of basic subsistence skills that would have allowed a predatory component to be added to an omnivorous collecting pattern. This subsistence pattern of linked collecting and predatory components could then have served as a basis for the development of a gathering-hunting subsistence pattern in which the behavioral elements of the two components had become specialized, and largely independent of each other. Chimpanzees and baboons are the only living primates for which there is evidence of the development of clear cut collecting-predatory subsistence behavior. However, it would be unwise to assume that the development of such a pattern in early hominids necessarily showed all the features of one, the other, or both of these patterns. Early hominids were obviously not morphologically or behaviorally identical to living ground adapted cercopithecines or pongids, and a one to one correspondence between the behaviours and social dynamics of living primates and early hominids is not to be expected. However, it is reasonable to postulate that some general features both of omnivorous collecting behavior, and of collecting-predatory behavior of early hominids may have been similar to those of living primates. Chimpanzee and baboon predatory patterns can perhaps best be seen as indicating two possible pathways by which predatory behavior can emerge from omnivorous collecting behavior. While the close phylogenetic relationship between chimpanzees and humans might make more direct reconstruction of early hominid predatory and other behavioral patterns an attractive proposition (e.g. Goodall & Hamburg, 1974), this requires fairly far reaching assumptions to be made (with dangers o f circular reasoning) about the nature of ancestral pongid and hominid populations and the degrees of divergence of modern pongids and humans from them. More extensive direct fossil and paleoecological data will be required for more detailed conclusions to be reached. Certainly, such cranial, dental and post-cranial evidence as exists suggests a fairly rapid divergence of the early hominid line or lines from the common hominoid stock. So far, the only really fixed point in the process would seem to be for the later hominids, where direct evidence suggests that big-game hunting, tool use, and possibly food sharing had become established in at least some populations (Isaac et al., 1976). Whether the emergence of predatory behavior in hominids followed a change in the herbivorous component of early hominid subsistence patterns (e.g. Jolly, 1970; Dunbar, 1976), developed along with it (e.g. Teleki, 1975), or developed in the absence of it (e.g. Szalay, 1975) is a matter for debate. T h a t the same morphological evidence can be used to support the first and last of these possibilities for some fossil species implies that either a detailed enough knowledge of the functional significance of some morphological features is lacking, or that the second possibility may be more likely (or perhaps that a
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human emotional Heisenbergian effect of the type discussed by Washburn & Ciochon (1974) may be in operation in thinking about these topics). It is not the purpose of this discussion to investigate the proximal or ultimate factors eliciting predatory behavior, nor the possible advantages such behavior may confer on those populations practicing it, although consideration of these factors will be of obvious importance in reconstructing the subsistence behavior of early hominids. Some of the possible factors involved in living primates have been discussed in some detail by Teleki (1975), Strum (t975, 1976), Pelham & Burton (1976), Gaulin & Kurland (1976) and Hausfater (1976). The indications are that subsistence behaviors of primates in general are not amenable to an easy analysis in terms of ecological, general nutritional, bioenergetic, or strategic factors. This would seem to be especially so with sporadic and low incidence behaviors such as predation, particularly where the evolutionary emergence of such behaviors is concerned. As Strum (1976) points out, the emergence of such patterns may be a compromise fit between what is ideally best and what is actually possible in the presence of constraining factors of many types. Thus suggestions that the predatory behavior of the Gombe chimpanzees (Wrangham, 1974; Reynolds, 1975) and perhaps the Gilgil baboons (Gaulin & Kurland, 1976) may in a sense be artifacts resulting from human intervention or other "non-natural" effects do not lead to insurmountable difficulties. The point of interest in evolutionary terms is that predatory behavior c a n develop, given certain basic subsistence skills, whatever the context of its emergence may be. Any new situation encouraging the development of new behaviors is, because of its novelty, "non-natural" in terms of what has gone before. The development of collecting-predatory subsistence patterns in early hominid populations must have depended on certain processes, regardless of the nature of the basic subsistence skills, and of the factors causing the shift towards the new pattern. These processes include the ways by which individual idiosyncracies become useful habits (Goodall & Hamburg, 1974), by which useful habits spread within local populations to become a longer or shorter lasting tradition (that can be developed, lost and redeveloped perhaps in slightly different form), and by which local traditions develop into fixed behavior patterns in the population at large. It is the behaviors already existing in the population that provide the substrate for these processes. The direction of the process may then be chanelled by more general processes of ecological change. Although changes in subsitence behavior must have been of the greatest importance in human evolution, changes of other types were undoubtedly of equal importance. Indeed, much of the ongoing paleoanthropological debate revolves around the stimuli for and the timing of changes in different aspects of morphology and behavior in hominids and their interplay in terms of positive feedback effects. The links between changes in subsistence patterns and changes in patterns of social organization are likely to have been particularly close, and evidence from chimpanzee predation especially has been used to suggest possibilities concerning the social organization of populations of collectingpredatory hominids (Teleki, 1975; King, 1975, 1976). Much of the attraction of theuse of evidence from the social carnivores also lies in the speculations it makes possible about the possible course of the evolution of human or hominid social organization during a time when predatory or hunting behavior had become a relatively large component of the total subsistence pattern. As well as making the fairly safe assumption that there a r e relationships between social organization and subsistence patterns, this approach also assumes that in its evolutionary development the human subsistence pattern has con-
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verged on the social carnivore pattern. However, it is obvious that as far as the subsistence patterns themselves are concerned the evidence from social carnivores is only relevant to the hunting component of the h u m a n pattern, and particularly to the large-game hunting element of this component. I t is also evident that this evidence is only applicable to the postulated stages of the h u m a n pattern after this convergence had taken place. It is difficult to see how this type of evidence can be of use for speculations concerning the development of subsistence patterns towards this point of convergence; early hominids were primates, not carnivores. Thus Thompson's (1975) view that both h u m a n and chimpanzee subsistence patterns are atypical of primate patterns and are convergent with those of social carnivores leaves these atypical patterns in a kind of limbo as far as their development is concerned. Evidence from other living carnivores might provide interesting comparative evidence concerning subsistence patterns themselves, rather than associated types of social organization. Information on the predatory-collecting behavior of some procyonid and ursid carnivores could be of special interest to thinking about the subsistence patterns of hominids in which the predatory component of a collecting-predatory pattern were marked, or in which a gathering-hunting pattern was developing. The manipulatory behavior of some procyonids, such as the racoon (Procyon lotor) and the occasional bipedalism of some ursids, both of which behaviours m a y be used in foraging and feeding behaviors, are other features of the biology of these forms relevant to ideas about hominid and h u m a n evolution. I n the above discussion an attempt has been made to give (like Harding, 1975) a uniformitarian view of the emergence of h u m a n subsistence behavior that is consistent with what is known about similar types of behavior in living primates, and to indicate some areas where caution might be advisable in order to avoid postulating too precise correspondences between hypothetical behavior in extinct hominids with that of extant mammalian species. All species are unique, although modern humans exhibit a number of features that seem to set the species somewhat apart from other primates. While these features are, in their fully developed forms, of interest in themselves, their development out of more characteristically primate roots is of equal interest. In this respect subsistence behavior is no exception.
I would like to thank R. S. O. Harding, D. Pilbeam, D. Post, A. Richard, S. C. Strum and G. Teleki for their comments on a preliminary draft of this paper.
References
Altmann, S. A. & Altmann, J. (1970). Baboon Ecology : African Field Research. Bibliotheca Primatologica, 12. Basel: Karger. Casimir, M.J. & Butenandt, E. (1973). Migration and core area shifting in relation to some ecological factors in a mountain gorilla group (Gorilla gorilla berengei) in the Mt. Kahuzl region (R6publique du Za~re). Zeitschriftf~r Tierpsychologie 33, 514-522. Chalmers, N. R. (1968). The social behaviour of free-living mangabeys in Uganda. Folia primatologica 8, 236-281. Crook, J. H. & Aldrich-Blake, P. (1968). Ecologicaland behavioral contrasts between sympatrie ground dwelling primates in Ethiopia. Folia primatologica 8, 192-227. Dunbar, R. I. M. (1976). Australopithecine diet based on a baboon analogy. Journal of Human Evolution 5, 161-167.
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Fossey, D. (1974). Observations on the home range of one group of mountain gorillas (Gorilla gorilla berengei). Animal Behaviour 22, 568-581. Frisch, J. E. (1968). Individual behavior a n d intertroop variability in Japanese macaques. In (P. C. Jay, ed.) Primates. Studies in Adaptation and Variability, pp. 243-252. New York: Holt, Rinehart and Winston. Gaulin, S . J . C . & Kurland, J. A. (1976). Primate predation and bioenergetics. Science 191, 314-315. Gautier-Hion, A. (1970). L'organisation sociale d'une bande de talapoins (Miopithecus talapoin) dans le Nord-Est du Gabon. Folia primatologica 12, 116-141. Goodall, J. & Hamburg, D. A. (1974). Chimpanzee behavior as a modeI for the behavior of early man. New evidence on possible origins of h u m a n behavior. In (D. A. H a m b u r g & H. K. H. Brodie, eds) American Handbook of Psychiatry, Vol. 6, pp. 14-43. New York: Basic Books. Hall, K. R. L. (1962). Numerical data, maintenance activities and locomotion of the wild chacma baboon, Papio ursinus. Proceedingsof the Zoological Society of London 139, 181-220. Hall, K. R. L. (1965). Behaviour and ecology of the wild pates monkey, Erythrocebuspatas, in Uganda. Journal of Zoology, London 148, 15-87. Harding, R. S. O. (1973a). Predation by a troop of olive baboons (Papio anubis). American Journal of Physical Anthropology 38, 587-592. Harding, R. S. O. (1973b). Range utilization by a troop of olive baboons (Papio anubis). Dissertation. University of California, Berkeley. Harding, R. S. O. (1974). The predatory baboon. Expedition 16, 30-39. Harding, R. S. O. (1975). Meat-eating and hunting in baboons. In (R. H. Tuttle, ed.) Socioecologyand P~ychology of Primates, pp. 245-257. The Hague: Mouton. Harding, R. S. O. & Strum, S. C. (1976). The predatory baboons of Kekopey. Natural History (New York) 85 (3), 46-53. Hausfater, G. (1976). Predatory behavior of yellow baboons. Behaviour 56, 44-68. Hladik, C. M. (1973). Alimentation et activit6 d'un groupe de chimpanzds r6introduits en for~t gabonaise. La Terre et la Vie 27, 343-413. Isaac, G. LI., Harris, J. W. K. & Crader, D. (1976). Archeological evidence from the Koobi Fora Formation. In (Y. Coppens, F. C. Howell, G. L1. Isaac & R. E. F. Leakey, eds) Earliest Man and Env#onments in the Lake Rudolf Basin, pp. 533-551. Chicago : University of Chicago Press. Itani, J. (1958). O n the acquisition and propagation of a new food habit in a troop of Japanese Monekys at Takasakiyama. Prhnates 1, 84-98. Jolly, C.J. (1970). The seed eaters: a new model of hominid differentiation based on a baboon analogy. Man 5, 1-26. Kawabe, M. (1966). One observed case of hunting behavior among wild chimpanzees living in the savanna woodland of western Tanganyika. Primates 7, 393-396. Kawai, M. (1965). Newly acquired pre-cultural behavior of the natural troop of Japanese monkeys on Koshima islet. Primates 6, 1-30. Kawamura, S. (1959). T h e process of subculture propagation among Japanese monkeys. Primates 2, 43-60. Kawamura, S. (1965). Subculture among Japanese monkeys. In (S. Kawamura & J. Itani, eds) Monkeys and Apes, pp. 239-292. Tokyo: Chuohoron-sha. King, G. E. (1975). Socioterritorial units among carnivores and early hominids. Journal of Anthropological Research 31, 69-87. King, G. E. (1976). Society and territory in h u m a n evolution. Journal of Human Evolution 5, 323-332. Lee, R. B. (1968). What hunters do for a living, or, how to make out on scarce resources. In (R. B. Lee & I. DeVore, Eds) Man the Hunter, pp. 30-48. Chicago : Aldine. Lee, R. B. (1972). The Kung bushmen in Botswana. In (M. G. Bicchieri, ed.) Itunters and Gatherers Today, pp. 327-368. New York: Holt, Rinehart & Winston. Lee, R. B. & DeVore, I. (1968). Problems in the study of hunters and gatherers. In (R. B. Lee & I. DeVore, eds) Man the Hunter, pp. 3-12. Chicago: Aldine. Maples, W. R. (1969). Adaptive behavior of baboons. American Journal of Physical Anthropology 31, 107110. Maples, W. R., Maples, M. K., Greenhood, W. F. & Walek, M. L. (1976). Adaptations of crop-raiding baboons in Kenya. American Journal of Physical Anthropology 45, 309-316. McGrew, W. C. (1975). Patterns of plant food sharing by wild chimpanzees. I n (S. Kondo, M. Kawai & A. Ehara, eds) Contemporary Primatology. Proceedings of the 5th International Congress of Primatology, pp. 304-309. Basel: Karger. Parker, C. E. (1974). The antecedents of m a n the manipulator. Journal of Human Evolution 3, 493-500. Pelham, A. de & Burton, F. D. (1976). More on predatory behavior in n o n h u m a n primates. Current Anthropology 17, 512-513. Reynolds, V. (1975). How wild are Gombe chimpanzees? Man 10, 123-125.
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Ripley, S. (1970). Leaves and leaf monkeys: the social organization of foraging in grey langurs Presbytis entellus thersites. I n (J. R. Napier & P. H. Napier, eds) Old World Monkeys, pp. 481-509. New York: Academic Press. Rose, M. D. (1977). Positional behaviour of olive baboons (Papio anubis) a n d its relationship to maintenance and social activities. Primates 18, 59-116. Schaller, G. B. & Lowther, G. R. (1969). The relevance of carnivore behavior to the study of early hominids. Southwestern Journal of Anthropology 25, 307-341. Struhsaker, T. T. (1967). Ecology of vervet monkeys (Cercopithecus aethiops) in the Masai-Amboseli Game Reserve, Kenya. Ecology 48, 891-904. Struhsaker, T. T. (1974). Correlates of ranging behavior in a group of red colobus monkeys (Colobus badius tephroseeles). American Zoologist 14, 177-184. Strum, S. C. (1975). Primate predation: an interim report on the development of a tradition in a troop of olive baboons. Science 187, 755-757. Strum, S. C. (1976). Primate predation and bioenergetics. Science 191, 315-317. Sugiyama, Y. (1969). Social behavior of chimpanzees in the Budongo Forest, Uganda. Primates 10, 197-225. Szalay, F. S. (1975). Hunting-scavenglng protohominids: a model for hominid origins. Man I0, 420-429. Teleki, G. (1973a). The Predatory Behavior of Wild Chimpanzees. Lewisburg: Bucknell University Press. Teleki, G. (1973b). The omnivorous chimpanzee. Scientific American 228, 32-42. Teleki, G. (1975). Primate subsistence patterns: collector-predators and gatherer-hunters. Journalof Human Evolution 4, 125-184. Thompson, P. R. (1975). A cross-species analysis of carnivore, primate and hominid behavior. Journal of Human Evolution 4, 113-124. Thompson, P. R. (1976). A behavior model for Australopithecus afrivanus. Journal of Human Evolution 5, 547-558. V a n Lawick-Goodall, J. (1968). The behaviour of free-living chimpanzees in the Gombe Stream Reserve. Animal Behaviour Monographs 1, 161-311. V a n Lawick-Goodall, J. (1971). In the Shadow of Man. New York: Houghton-Mifflin. Warren, J. M. (1974). Possibly unique characteristics of learning by primates. Journal of Human Evolution 3, 445-454. Washburn, S. L. & Ciochon, R. L. (1974). Canine teeth: notes on controversies in the study of h u m a n evolution. American Anthropologist 76, 765-784. Wrangham, R. W. (1974). Artificial feeding of chimpanzees and baboons in their natural habitat. Animal Behavlour 22, 83-93. Yamada, M. (1957). A case of acculturation in a subhuman society of Japanese monkeys. Primates 1, 30-46. Yerkes, R. M. & Yerkes, A. W. (1935). Social behavior in infrahuman primates. I n (C. Murchison, ed.) A Handbook of Social Psychology, pp. 973-1033. Worcester: Clark University Press.
Received 3 May 1977 and accepted 15 July 1977 Keywords : subsistence patterns, predation, human evolution, Papio, Cercopitheeusaethiops, Pan troglodytes.
The Roots of P r i m a t e Predatory Behavior Evidence is examined that supports the view that in collectingpredatory primates many of the behaviours associated with the predatory component of the subsistence pattern are similar to those occurring during omnivorous collecting activities. General similarities are found between some elements of predatory behavior and some overall features of omnivorous foraging and feeding, and more specific similarities are found with collecting behavior directed towards rarely occurring, clumped, or highly favoured plant foods. It is suggested that there are few elements in primate predatory behavior that require more than the general behavioral plasticity and adaptability that omnivorous, ground foraging primates exhibit with respect to the exploitation of different types of plant foods. The emergence of the gathering-hunting human subsistence pattern out of a collecting-predatory pattern that was in turn based on omnivorous collecting is a model for an evolutionary pathway that is consistent with both direct and comparative evidence. While the comparative evidence enables some general features of this model to be described, caution is advised about applying more detailed features of the subsistence behavior of non-human mammals to the postulated subsistence patterns of hominid populations the morphology and behavior of which were not identical to those of living primate or other mammalian species.
1. I n t r o d u c t i o n T h e fossil a n d o t h e r d i r e c t evidence for the evolution o f h u m a n subsistence p a t t e r n s is p a t c h y a n d equivocal. I n t e r e s t in this aspect o f h u m a n e v o l u t i o n is c u r r e n t l y m a i n t a i n e d b y evidence o f three m a i n types in a d d i t i o n to the d i r e c t evidence. Studies o f c o n t e m p o r a r y h u m a n p o p u l a t i o n s i n d i c a t e t h a t the basic h u m a n subsistence p a t t e r n is b r o a d l y b a s e d (e.g. Lee, 1968, 1972; Lee & D e V o r e , 1968). T e l e k i (1975) suggests t h a t t h e t e r m g a t h e r i n g - h u n t i n g , r a t h e r t h a n h u n t i n g or h u n t i n g - g a t h e r i n g , best describes the p a t t e r n . A s e c o n d line o f evidence is used to p o i n t o u t parallels b e t w e e n the social o r g a n i z a t i o n a n d subsistence p a t t e r n s of some social carnivores a n d some features o f the basic h u m a n p a t t e r n (e.g. S c h a l l e r & L o w t h e r , 1969; K i n g , 1975, t 9 7 6 ; T h o m p s o n , 1975, 1976). T h e t h i r d line of a p p r o a c h seeks to relate h u m a n g a t h e r i n g - h u n t i n g p a t t e r n s to c o l l e c t i n g p r e d a t o r y p a t t e r n s o f n o n - h u m a n p r i m a t e s (e.g. Teleki, 1975; H a r d i n g , 1975). T h e attractiveness o f the t h i r d a p p r o a c h is t h a t it allows c o m p a r i s o n s to be m a d e b e t w e e n the t o t a l h u m a n subsistence p a t t e r n a n d those o f the n o n - h u m a n p r i m a t e s c o n c e r n e d . Differences b e t w e e n the p a t t e r n s c a n be seen to be o f d e g r e e r a t h e r t h a n k i n d (e.g. Teleki, 1975). Despite p o t e n t i a l a n d a c t u a l difficulties in using evidence from living n o n - h u m a n m a m m a l s , Schaller & L o w t h e r (1969) a n d K i n g (1975) suggest t h a t evidence o f the t h r e e types m a y all b e useful for ideas c o n c e r n i n g different phases of the evolution o f the h u m a n p a t t e r n . Teleki (1975) a n d K i n g (1975) b o t h suggest t h a t some of the e l e m e n t s o f the p r e d a t o r y c o m p o n e n t o f the c o l l e c t i n g - p r e d a t o r y p a t t e r n s of living p r i m a t e s m a y h a v e o r i g i n a t e d in o m n i v o r o u s collecting b e h a v i o r . E v i d e n c e from the b e h a v i o r o f nonh u m a n m a m m a l s is thus u s e d to g e n e r a t e hypotheses c o n c e r n i n g the evolution o f h u m a n subsistence p a t t e r n s in the b i g - g a m e h u n t i n g phase (social c a r n i v o r e models) a n d in a Journal of Human Evolution (1978) 7, 179-189
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pre big-game hunting, collecting-predatory phase (baboon and chimpanzee models). Given the possibility that human gathering-hunting behavior may have had its origin in a hominid collecting-predatory pattern, speculations concerning the origin of the collecting-predatory pattern in even earlier hominid or hominoid subsistence behavior becomes of interest. This paper examines in more detail the suggestions of especially Teleki (1975), that some elements of the predatory behavior of living collector-predators may have arisen out of omnivorous collecting behavior. The results of this examination are then discussed in relationship to the possible course of the evolution of human subsistence patterns. Evidence will be examined concerning general aspects of the subsistence patterns of omnivorous, more terrestrially based primates, but attention will also be paid to subsistence behaviors related to plant food types that (like some types of animal food) require specialized techniques of collection, are patchily distributed in space and time, may have specific valuable nutritional components, may require changes in normal ranging patterns for their harvesting, or are favoured food items. Personal observations have been made on a number of primate species, during several years' field work in East Africa. Observations particularly relevant to this paper were made on olive baboons (Papio anubis), and vervet monkeys (Cercopithecus aethiops) in various habitats in Uganda and Kenya. Feeding behavior related to special plant foods, particularly the prickly pear cactus (0puntia vulgaris), has mainly been observed during field studies of collecting-predatory olive baboons at Gilgil, Kenya, and of vervet monkeys at Naivasha, Kenya.
2. Predatory Behavior and O m n i v o r o u s Collecting Teleki (1975) divides the predatory behavior of chimpanzees into a number of stages involving, in sequence, the pursuit, capture and consumption of the prey animal. Baboon predatory behavior may also involve these stages (Harding, 1974; Harding & Strum, 1976; Hausfater, 1976). Teleki recognizes three alternative pursuit modes; seizure, chasing and stalking, and relates seizure to normal manipulatory behaviors occurring during omnivorous collection. While chasing as such rarely occurs during the collection of plant foods, both olive baboons and vervet monkeys chase after and seize flying insects, often running bipedally to do so. The stalking of larger animal prey might seem to be a behavior pattern specifically associated with this type of food item. However, stalking is a particular example of a general strategy of approach to all types of food object that maximizes the chance of obtaining the object, while as far as possible minimizing the effort involved and the danger risked by the animal concerned. The patterning of activities is similar regardless of food type, even if individual behavioral elements may differ. Parallels with predatory stalking become closer in activities such as the gathering of prickly pear fruit by vervet monkeys. The fruit themselves and the plant on which they grow are extremely spiney and the plants form complicated branching masses up to about three meters in height. Vervet monkeys at Naivasha spend considerable periods of time pacing around the base of these plants to locate a ripe fruit in an accessible position. They then pick their way with great care up through the plant, sometimes halting to get a visual fix on the chosen fruit before continuing up and through the plant. This sequence of behaviors shows just those elements of premeditation and decision making that Teleki (1975) associates with chimpanzee chasing and stalking, and which may also occur in baboon predatory behavior (Harding,
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1973a, 1974; Strum, 1975; Harding & Strum, 1976; Hausfater, 1976). This plasticity of behaviour is also seen in other aspects of the "stalking" of prickly pear fruit by vervet monkeys. During the collection of most commonly occurring food objects in aboveground settings, food that is inadvertently dropped is virtually never followed to the ground and retrieved. However, because the gathering of prickly pear fruit involves the delicate removal of the fruit from the stem by a careful, usually one-fingered levering movement, the fruit frequently drops to the ground when it separates. In this case the vervet will follow the ~?uit to the ground, using another carefully picked out pathway through the plant, search out the fruit on the ground, and then consumes it. While to the human observer this seems an obvious behaviour pattern to follow, it nevertheless represents a pattern that departs radically from those occurring during regular food gathering. Olive baboons also modify behavior patterns to fit exceptional circumstances. Crook & Aldrich-Blake (1968) describe a stroking technique used by some olive baboons to to detach prickly pear leaves. Olive babooons at Gilgil use a different technique involving a downward levering movement of one or two finger tips applied to the end of the leaf (Rose, 1977). In each case the baboons were faced with a challenging food acquisition problem, which they solved by drawing on their manual and mental skills. Different collection techniques may also be developed by different age classes of a population during such activities as rock-turning in order to collect hidden invertebrates (Rose, 1977). The techniques differ in these instances, but the abilities involved are the same, and it is abilities such as these that must be called into play when the more complex problems of acquiring mobile animal food objects arise. Another aspect of predatory behavior of both chimpanzees and olive baboons is that the chasing and stalking behaviours utilized involve a degree of persistence, in terms of time spent attempting to acquire a food object, and of the number of attempts made, that rarely occurs during normal types of foraging (Teleki, 1975; Harding & Strum, 1976). However, the behaviour of both olive baboons and vervet monkeys in acquiring prickly pear plant parts indicates that if the food object is prized highly enough animals will persist until they have achieved their ends. Olive baboons digging for underground plant parts, or searching for and extracting honeycomb show a similar persistence, as do chimpanzees gathering honey or bird eggs (Van Lawick Goodall, 1968). These instances of premeditation, decision-making and general behavioral plasticity are all examples of the sophisticated cognitive skills and the capacity for acquiring abstract general strategems and response rules that Warren (1974) suggests differentiate primates from other mammals. These abilities seem to be particularly well developed in those broad-niched primates characterized by Struhsaker (1976) as "opportunistic omnivores" and by Parker (1974) as "opportunists", and are exhibited in a number of contexts related to foraging. Thus Hall (1962) points out that chacma baboons (Papio ursinus) rapidly develop effective manipulatory and exploratory skills that can be successfully generalized to a wide variety of problems related to food. A number of studies on Japanese macaques (Macacafuscata) have provided a detailed analysis of how these skills can be developed in novel feeding situations (e.g. Yamada, 1957; Itani, 1958; Kawamura, 1959, 1965; Kawai, 1965; Frisch, 1968). Predation by olive baboons at least, sometimes involves individuals or groups of animals changing their normal ranging patterns in order to seek out or pursue prey animals (Harding, 1973a; Strum, 1975). Long or short term variations in normal ranging patterns
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may be associated with a wide variety of factors o f which changes in resource availability and distribution, and the presence of other (conspecific) animal groups are two examples (e.g. Casimir & Butenandt, 1973; Fossey, 1974; Struhsaker, 1974). The vervet monkeys at Naivasha suddenly and drastically changed their ranging pattern, coincidentally with the ripening of the fruit of a localized area of prickly pear plants. Perhaps of more direct relevance to predatory behavior are variations in the foraging behavior of an individual or age-sex class. Sex differences in foraging patterns, or in diet, or both occur in the Gilgil olive baboons (Rose, 1977) and in yellow baboons (Papio cynocephalus) at Amboseli, Kenya (Post, pets. comm.). A more idiosyncratic example involved an adult male vervet monkey at Naivasha, that would regularly range away from the rest of its troop in order to investigate outlying stands of prickly pear plants. Altmann & Altmann (1970) and Post (pers. comm.) have observed similar excursions being made by yellow baboons to feed on fever tree gum. These examples, together with most observations of predatory behavior, indicate that there are sex differences in some aspects of ranging and foraging behavior that, as Teleki (1975) points out, have some relevance to a discussion of the origin of the division of labor that may occur in human gathering-hunting subsistence patterns. Teleki (1973a,b, 1975) mentions that more than one animal may be involved in chimpanzee predatory episodes, often acting in co-operation with each other. Strum (1975) and Harding & Strum (1976) have documented the development of a less complex co-operative pattern of relay chasing, out of individual chasing of animal prey by olive baboons. Co-operative behavior of these types is not seen in other types of food acquisition. However, there are a number of situations related to foraging and feeding where behaviors showing similar features do occur. While aggressive behavior is relatively common at clumped or highly favoured food sources (e.g. Hall, 1965; Chalmers, 1968; Gautier-Hion, 1970; Harding, 1973b; Wrangham, 1974) there are many situations where the spacing, orientation and interactions of individuals represents a type of co-operation that allows them to feed at the same site without aggression breaking out (e.g.Ripley, 1970). One aspect of the co-operative predation of both chimpanzees and olive baboons is that it entails the direction of the activities of different animals towards, and their physical convergence on the same food source. There are some situations, especially involving highly prized plant food items, where similar behavior is seen. Thus the investigation of outlying prickly pear clumps by the adult male vervet monkey mentioned above sometimes resulted in a few other animals, usually juvenile males, leaving the troop and converging on the same food source from different directions. This convergence never led to co-operative food acquisition by these vervet monkeys. However, the unintentionally co-operative behavior of relay chasing and eventual capture of prey animals by the Gilgil baboons indicates that this type of convergence can form the basis for more useful predatory behaviors, whether they are intentional or not. A more sophisticated type of co-operation has been observed by Maples (1969) in olive baboons raiding maized fields. Three types of diversionary tactics, one of which involved coalitions of males, females, and infants, were used to allow other troop members, sometimes acting as separate but coordinated raiding parties, to get to the maize. Maples et al. (1976) suggest that these may not be intentionally diversionary tactics, but that they result from the social subgrouping of the troops concerned, and the particular distribution of natural and man-made habitats in which the troops are active. This makes these instances even more
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interesting in the present context, as it shows the extent to which normal features of a species' life can combine to bring about what is in effect a new type of behavior. Teleki (1975) defines a stage of capture following a successful predatory pursuit by chimpanzees, which involves a succession of behaviors by which the prey is caught, killed and initially divided. The lunging and grasping movements associated with catching also occur during omnivorous collecting. Similarly the killing of prey animals, which either occurs incidentally as the animal is eaten to death, or as a result of neck biting or twisting, contains few elements that are not involved in the consumption of the tougher types of plant food. The specialized technique by which chimpanzees beat an animal to death by flailing it against a solid surface also involves behaviors normally used in feeding, aggression and display (Van Lawick Goodall, 1968, 197 I). Teleki (1975) points out that as in human hunting, there may be a stage in chimpanzee predation between the acquisition of a prey item and its consumption, during which the food is transported away from the kill site. Ground living primates sometimes transport plant foods, particularly in situations where animals are crowded at a rarely occurring or highly favoured food source. By removing itself and its food from the acquisition site the animal minimizes its chances of becoming involved in aggressive interactions and of having its food appropriated. In cercopithecines the food is usually carried in the mouth. Vervet monkeys at Naivasha and olive baboons at Gilgil transport prickly pear plant parts in this way, and these species have been observed transporting mushrooms, berry bearing twigs, and larger fruit at a number of sites. Other objects, ranging from infants to tools, are also transported by some primates in a variety of situations. Transporting behavior is thus a part of the behavioral repertoire of a number of primate species, and its specific association with predatory or hunting behavior again represents no more than the application of an existing ability in a new situation. T h e final stages of predatory episodes involve the dismantling and distribution of the prey item for consumption. Both chimpanzee and baboon groups sometimes share meat at this stage. Chimpanzees have also been observed sharing plant foods (Sugiyama, 1969; Hladik, 1973; McGrew, 1975). McGrew suggests that the sharing of meat may represent a more recent and specialized evolutionary development in chimpanzees, based on the phylogenetically more primitive pattern of plant food sharing. While the pattern of meat sharing in chimpanzees involves exceedingly complex interactions, Teleki (1975) has stressed that this distribution is along lines determined more by special dyadic relationships rather than by special rank (confirming the conclusions of Yerkes & Yerkes (1935) based on the observation of captive chimpanzees). Hladik (1973) and Savage, quoted in McGrew (1975) suggest that the mother-infant dyad may have special importance, which supports Van Lawick Goodall's (1968) suggestion that the begging gestures associated with food sharing, together with similar gestures associated with submission, reassurance , or grooming interactions, may all be related to gestures originally occurring in m o t h e r infant interactions. Kawabe (1966) provides evidence from a single predatory episode that rank behavior may in fact break down at a kill site, and suggests that this in itself m a y be a pre-adaptation to sharing. While meat distribution among baboons is less complex than in chimpanzees, Hausfater (1976) points out that it may be just as extensive. This distribution is made possible by a variety of factors, ranging from behaviors such as the "vulture response" (Altmann & A]tmann, 1970; Harding, 1973a, 1975) of baboons converging on a kill site (sometimes occurring with plant foods, as described above), to social factors such as mother-infant,
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infant-adult male, consort, play group or other relationship (Strum, 1975; H a r d i n g & Strum, 1976). T h e Gilgil olive baboons, and the Naivasha vervets both show sharing-like behaviors involving animals feeding from the same object or portions thereof, either in the context of the mother-infant dyad, by aggressive displacement, or by the retrieval of food dropped by another animal. T h e foods involved include mushrooms, some fleshy fruits, and prickly pear fruit a n d leaves. Thus while the fully developed patterns of food sharing of the h u m a n type m a y be rare a m o n g primates, even during predatory episodes, there does seem to exist a n u m b e r of behaviors and social relationships that can serve as a basis for the development of such patterns. 3. D i s c u s s i o n
The evidence examined above supports Teleki's (1975) suggestion that in some primate species there is a repertoire of maintenance and social behaviors that is utilizable, with or without some modification, in predatory situations. The precursors of predatory behavior seem to be most evident among the more terrestrial primates, living in open habitats, and with a relatively broad subsistence base associated with an extensive repertoire of collecting behaviors. These facts are relevant to a consideration of the evolutionary development of h u m a n subsistence behavior. There is an almost unavoidable bias to thinking about this subject. As with other "unique" and important h u m a n characteristics, such as language, tool use, and striding bipedalism there is a double temptation, to either minimize the relevance of these characteristics to the h u m a n condition when they occur in a m u t e d or differently developed form in other species or, if their relevance is admitted, to attribute the same aura of specialness to them as is associated with their expression in humans. I t is the latter temptation that is perhaps the stronger with repect to thinking about the hunting component of h u m a n subsistence patterns and the predatory component of non-human primate collecting-predatory subsistence patterns. Whether or not h u m a n subsistence patterns are considered to be unique, the gathering and hunting components of the gathering-hunting pattern involve different behavioral elements that bear little obvious relationship to each other. I n addition, the hunting component would seem to require a n u m b e r of specialized behaviors. However, speculations concerning the development of these behaviors might be more profitable if, instead of projecting concepts of uniqueness backward in time, emphasis is placed on the possible development of new patterns out of more recognizably '"ordinary" components. One likely place to seek for these components in the case of hunting behavior is in predatory behavior similar to that exhibited by some living primate species. Predatory behaviour involving larger animal prey would not seem to be of more than marginal importance in populations at large of non-human primates, but because of its relevance to h u m a n hunting behavior, it has received a great deal of attention when it does occur. This tendency is not helped by the fact that in at least one population, predatory behavior has been seen to develop very rapidly. However, this very fact should serve to indicate that what is occurring is not necessarily arising de novo but m a y be a new expression of existing behaviors of the individuals and populations concerned. , J u s t as h u m a n hunting is p a r t of a broader gathering-hunting pattern, so too is predatory behavior part of a much broader collecting-predatory pattern, but whereas in the h u m a n pattern the gathering and hunting components are clearly differentiated, there are obvious links between the limited predatory component and the more extensive
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collecting component of the collecting predatory pattern. As far as the human observer is concerned this predatory behavior may seem special, but as far as the animals involved are concerned larger animal prey may be just another food source, to be exploited by using the behaviours available for the exploitation of other food sources. These behaviors may well need to be modified in predation, but so may they for the exploitation of other food types. One of the few points of agreement concerning hominid evolution is that its early stages were associated with a shift to a more terrestrially based existence in more open habitats and with a change in, if not a broadening of the subsistence base. Given that such a shift took place, and that a gathering-hunting subsistence pattern was developed in at least some species of later hominids, it is consistent with the comparative evidence to suppose that early hominids possessed a repertoire of basic subsistence skills that would have allowed a predatory component to be added to an omnivorous collecting pattern. This subsistence pattern of linked collecting and predatory components could then have served as a basis for the development of a gathering-hunting subsistence pattern in which the behavioral elements of the two components had become specialized, and largely independent of each other. Chimpanzees and baboons are the only living primates for which there is evidence of the development of clear cut collecting-predatory subsistence behavior. However, it would be unwise to assume that the development of such a pattern in early hominids necessarily showed all the features of one, the other, or both of these patterns. Early hominids were obviously not morphologically or behaviorally identical to living ground adapted cercopithecines or pongids, and a one to one correspondence between the behaviours and social dynamics of living primates and early hominids is not to be expected. However, it is reasonable to postulate that some general features both of omnivorous collecting behavior, and of collecting-predatory behavior of early hominids may have been similar to those of living primates. Chimpanzee and baboon predatory patterns can perhaps best be seen as indicating two possible pathways by which predatory behavior can emerge from omnivorous collecting behavior. While the close phylogenetic relationship between chimpanzees and humans might make more direct reconstruction of early hominid predatory and other behavioral patterns an attractive proposition (e.g. Goodall & Hamburg, 1974), this requires fairly far reaching assumptions to be made (with dangers o f circular reasoning) about the nature of ancestral pongid and hominid populations and the degrees of divergence of modern pongids and humans from them. More extensive direct fossil and paleoecological data will be required for more detailed conclusions to be reached. Certainly, such cranial, dental and post-cranial evidence as exists suggests a fairly rapid divergence of the early hominid line or lines from the common hominoid stock. So far, the only really fixed point in the process would seem to be for the later hominids, where direct evidence suggests that big-game hunting, tool use, and possibly food sharing had become established in at least some populations (Isaac et al., 1976). Whether the emergence of predatory behavior in hominids followed a change in the herbivorous component of early hominid subsistence patterns (e.g. Jolly, 1970; Dunbar, 1976), developed along with it (e.g. Teleki, 1975), or developed in the absence of it (e.g. Szalay, 1975) is a matter for debate. T h a t the same morphological evidence can be used to support the first and last of these possibilities for some fossil species implies that either a detailed enough knowledge of the functional significance of some morphological features is lacking, or that the second possibility may be more likely (or perhaps that a
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human emotional Heisenbergian effect of the type discussed by Washburn & Ciochon (1974) may be in operation in thinking about these topics). It is not the purpose of this discussion to investigate the proximal or ultimate factors eliciting predatory behavior, nor the possible advantages such behavior may confer on those populations practicing it, although consideration of these factors will be of obvious importance in reconstructing the subsistence behavior of early hominids. Some of the possible factors involved in living primates have been discussed in some detail by Teleki (1975), Strum (t975, 1976), Pelham & Burton (1976), Gaulin & Kurland (1976) and Hausfater (1976). The indications are that subsistence behaviors of primates in general are not amenable to an easy analysis in terms of ecological, general nutritional, bioenergetic, or strategic factors. This would seem to be especially so with sporadic and low incidence behaviors such as predation, particularly where the evolutionary emergence of such behaviors is concerned. As Strum (1976) points out, the emergence of such patterns may be a compromise fit between what is ideally best and what is actually possible in the presence of constraining factors of many types. Thus suggestions that the predatory behavior of the Gombe chimpanzees (Wrangham, 1974; Reynolds, 1975) and perhaps the Gilgil baboons (Gaulin & Kurland, 1976) may in a sense be artifacts resulting from human intervention or other "non-natural" effects do not lead to insurmountable difficulties. The point of interest in evolutionary terms is that predatory behavior c a n develop, given certain basic subsistence skills, whatever the context of its emergence may be. Any new situation encouraging the development of new behaviors is, because of its novelty, "non-natural" in terms of what has gone before. The development of collecting-predatory subsistence patterns in early hominid populations must have depended on certain processes, regardless of the nature of the basic subsistence skills, and of the factors causing the shift towards the new pattern. These processes include the ways by which individual idiosyncracies become useful habits (Goodall & Hamburg, 1974), by which useful habits spread within local populations to become a longer or shorter lasting tradition (that can be developed, lost and redeveloped perhaps in slightly different form), and by which local traditions develop into fixed behavior patterns in the population at large. It is the behaviors already existing in the population that provide the substrate for these processes. The direction of the process may then be chanelled by more general processes of ecological change. Although changes in subsitence behavior must have been of the greatest importance in human evolution, changes of other types were undoubtedly of equal importance. Indeed, much of the ongoing paleoanthropological debate revolves around the stimuli for and the timing of changes in different aspects of morphology and behavior in hominids and their interplay in terms of positive feedback effects. The links between changes in subsistence patterns and changes in patterns of social organization are likely to have been particularly close, and evidence from chimpanzee predation especially has been used to suggest possibilities concerning the social organization of populations of collectingpredatory hominids (Teleki, 1975; King, 1975, 1976). Much of the attraction of theuse of evidence from the social carnivores also lies in the speculations it makes possible about the possible course of the evolution of human or hominid social organization during a time when predatory or hunting behavior had become a relatively large component of the total subsistence pattern. As well as making the fairly safe assumption that there a r e relationships between social organization and subsistence patterns, this approach also assumes that in its evolutionary development the human subsistence pattern has con-
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verged on the social carnivore pattern. However, it is obvious that as far as the subsistence patterns themselves are concerned the evidence from social carnivores is only relevant to the hunting component of the h u m a n pattern, and particularly to the large-game hunting element of this component. I t is also evident that this evidence is only applicable to the postulated stages of the h u m a n pattern after this convergence had taken place. It is difficult to see how this type of evidence can be of use for speculations concerning the development of subsistence patterns towards this point of convergence; early hominids were primates, not carnivores. Thus Thompson's (1975) view that both h u m a n and chimpanzee subsistence patterns are atypical of primate patterns and are convergent with those of social carnivores leaves these atypical patterns in a kind of limbo as far as their development is concerned. Evidence from other living carnivores might provide interesting comparative evidence concerning subsistence patterns themselves, rather than associated types of social organization. Information on the predatory-collecting behavior of some procyonid and ursid carnivores could be of special interest to thinking about the subsistence patterns of hominids in which the predatory component of a collecting-predatory pattern were marked, or in which a gathering-hunting pattern was developing. The manipulatory behavior of some procyonids, such as the racoon (Procyon lotor) and the occasional bipedalism of some ursids, both of which behaviours m a y be used in foraging and feeding behaviors, are other features of the biology of these forms relevant to ideas about hominid and h u m a n evolution. I n the above discussion an attempt has been made to give (like Harding, 1975) a uniformitarian view of the emergence of h u m a n subsistence behavior that is consistent with what is known about similar types of behavior in living primates, and to indicate some areas where caution might be advisable in order to avoid postulating too precise correspondences between hypothetical behavior in extinct hominids with that of extant mammalian species. All species are unique, although modern humans exhibit a number of features that seem to set the species somewhat apart from other primates. While these features are, in their fully developed forms, of interest in themselves, their development out of more characteristically primate roots is of equal interest. In this respect subsistence behavior is no exception.
I would like to thank R. S. O. Harding, D. Pilbeam, D. Post, A. Richard, S. C. Strum and G. Teleki for their comments on a preliminary draft of this paper.
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