bond strength of a calcium silicate based sealer tested in bulk or with different main core materials

And males were observed to vie with each other aggressively for limited re-sources, organizing themselves into a stable dominance hierarchy that per-mitted most conflicts to be resolved

'DYLG.-RUGDQ0DUF-6ZDUW]

3XEOLVKHGE\7KH8QLYHUVLW\RI$ODEDPD3UHVV

'DYLG.-RUGDQDQG0DUF-6ZDUW]

3HUVRQDOLW\DQGWKH&XOWXUDO&RQVWUXFWLRQRI6RFLHW\

7XVFDORRVD7KH8QLYHUVLW\RI$ODEDPD3UHVV

3URMHFW086( :HE0DUKWWSPXVHMKXHGX

For additional information about this book

Access provided by New York University (1 Jun 2015 20:45 GMT)

http://muse.jhu.edu/books/9780817384081

Aggression, Social Skill, and Strategy

in Daily Life

A Baboon Case History

A paper on baboons may seem out of place in a volume concerned with cultural anthropology and specifically with its psychological aspects Yet although our subjects differ markedly, Melford Spiro and I share many interests Among the earliest, in both cases, was the challenge to explain aggression in daily life and, later, a fascination with the biological universals that may apply to human behavior

I present here not a review of animal aggression or of evolutionary theory but something different: a case history of a baboon group Here I follow a "Spiro axiom": "single cases prove little; they are primarily useful insofar as they challenge received opinions" (Spiro 1979a:109) The baboon case history suggests startling conclusions about how we should view aggres-sion in at least one animal society, and since models of human aggresaggres-sion have, for at least half a century, relied heavily on animal data, these become

"facts" relevant to our understanding of humans I will consider the manner

in which these facts might be used in analyses of human evolution

COMPETITION AND DEFENSE: SOCIAL SKILL OR BRUTE FORCE? The first scientific animal studies of this century identified aggression

as a pervasive element in daily life Until the 1930S, however, scientists viewed aggression as both abnormal and dysfunctional, since it seemed to disrupt the basic fabric of society The "ethologists" of the 1930S (Tinbergen 1953; Lorenz 1964; etc.) fundamentally changed our views when they at-tempted to understand animal behavior from an evolutionary point of view

(see Marler and Hamilton Ig66 for a general discussion) This evolutionary approach transformed aggression into an adaptive behavior, normal instead

of abnormal and central instead of dysfunctional in solutions to such animal problems as competition and defense Conceptually, aggression soon came

to be seen as an important evolutionary feature of animal society It also became a vital structural feature, since aggression often resulted in domi-nance hierarchies, ordering individual interactions, and through the indi-viduals, the group The practical significance of aggression suggested that, everywhere and for everyone, resources are necessarily limited (e g., food, water, sleeping and nesting places, mates) and that individual survival and success depended on obtaining these resources (See Alcock 1975; DeVore Ig65a; Lorenz 1966; Marler and Hamilton 1966.) Competition, defense, re-production, aggression, and dominance became interrelated dimensions of animal life

Anthropologists such as Sherwood Washburn added significantly to the developing evolutionary perspective on aggression, contributing a knowl-edge offunctional anatomy and primate evolution to the synthesis Washburn (Washburn and DeVore 1961; Washburn and Hamburg 1965, 1968; Wash-burn, Jay, and Lancaster 1965) emphasized the biological basis of aggression, noting that many physical differences between male and female nonhuman primates could be understood only in terms of the anatomy of aggression Drawing from the field data of the time (the late 1950S and early 1960s), he concluded that "there are marked species differences in aggressive behavior and in the dominance hierarchies that result from it Baboons and macaques are probably the most aggressive of the monkeys But interindividual conflict is important in all species described so far" (1968:471) "And in so-cieties of nonhuman primates aggression is constantly rewarded" (1968:417) Therefore "monkeys not only have the biological basis for aggressive be-havior, but also use this equipment frequently and success is highly re-warded" (1968:471)

The contrast between nonhuman and human primates allowed an-thropologists to chart the evolutionary transformation of aggression in the primate order Humans lack the anatomical structures used among the non-human primates in agonistic displays, and this characteristic suggested that

"the evolution of language as a more efficient method of social communi-cation including the communicommuni-cation of threat, changed the pressures on a wide variety of other structures that must have functioned in agonistic dis-play" (Washburn and DeVore 1961:747) "and opened the way to the existence

of a social system in which aggressive behavior is not constantly rewarded" (Washburn and Hamburg 1968:475)

In the course of human evolution, language made possible a new "com-plex social life" which itself modified the human body, human emotions,

330

and the human brain "Taken together, the new parts of the association areas and parts of the brain making language possible might be thought of as the 'social brain'-the parts of the brain that (from an evolutio'nary point of view) evolved in response to social pressures and the parts that today mediate appropriate social action" (Washburn and Hamburg 1968:478)

Thus aggression was seen as deeply rooted in primate anatomy and physiology and had a long and important evolutionary history, but both its biology and its function were significantly altered by the events in human evolution

More recently, studies of animal behavior have embraced a new theo-retical framework (see Wilson 1975 for a review) The classic ethologists and even the subsequent work spoke of evolutionary costs and benefits that were for the good of the "species" or the good of the "group." This formulation was at variance with modern genetics, which is based on the idea that the individual is the unit of selection Behavioral ecologists and sociobiologists

of the late 1970S shifted the focus of explanation and evolutionary interpre-tation from "group selection," which at best can exist only under very limited conditions (at least theoretically), to "individual selection." The units, whether genes (Dawkins 1976), individuals (Wilson 1975), kin groups sharing genes (Hamilton 1964), or pairs of unrelated individuals engaged in reci-procity (reciprocal altruism; rrrivers 1971), act in such a way that they survive and enjoy greater reproductive success relative to other such units

In these modern terms, an individual's reproductive success most often depends on the use of aggressive "strategies" of competition and defense Strategies incorporate various tactics,l and they involve behaviors (of gen-otypic or phengen-otypic origin) that increase an individual's "fitness." Fitness

is the relative reproductive success of a genotype as it finds expression in

an individual and in his close kin

There was an integral feedback relationship between baboon research and our modern ideas about aggression and dominance The baboon studies

of the last twenty years both fitted nicely with the new perspective on aggression and played a critical role in the elaboration of the perspective.2 Male baboon anatomy seemed to reflect an adaptation for aggression And males were observed to vie with each other aggressively for limited re-sources, organizing themselves into a stable dominance hierarchy that per-mitted most conflicts to be resolved on the basis of rank rather than by overt aggression The concepts of competition, aggression, and dominance helped explain baboon behavior Yet there were anomalous data from the beginning Field studies of other nonhuman primates hinted that aggression and domi-nance might not operate as simply or as effectively as had been assumed Even some baboon data did not fit (See especially the works by Rowell cited in note 2.) The evidence on coalitions between individuals facing an

aggressive antagonist3 and the role of female choice in successful male reproduction4created an informal challenge to the traditional position Against this backdrop, the case study of the Pumphouse baboons that

is presented here and elsewhere5offers even more serious objections to the traditional view The Pumphouse baboon anomalies, in order of their his-torical relevance, are that (1)there is no classic male dominance hierarchy, and aggressive/agonistic rank, when it can be determined, is not positively correlated with the acquisition of limited resources; (2) there is generally little intermale aggression, yet males are superbly equipped for aggression, and a stable male dominance hierarchy is absent; and (3) friendships exist (of greatest interest are those between males and females and between males and infants) Before we can explore the significance of these anomalies, we must briefly consider a few baboon basics

BABOON BASICS Our subjects are a group ofbaboons, called a "troop," that until recently lived on45,000privately owned acres near the town of Gilgil, in the Central Rift Valley of Kenya The troop, named the Pumphouse Gang, inhabited an open savannah which they shared with other anilnals, both wild and do-mestic, and with a growing human population A baboon troop can range in size from as few as 20 animals to as many as 140 animals; the large groups result from high infant survival and the addition of adolescent and adult males who migrate between groups in a population

Observation on Pumphouse began in 1970 My own research started

in 1972 and has continued until the present A baboon's lifetime is more that thirty years for females and slightly less for males The current study thus represents a significant period of time from the perspective of baboon lifespan

A baboon troop is not a random assortment of individuals; it has a basic composition and a basic structure Adult females outnumber adult males, two or three to one, but adults are in the minority; immature animals form the troop's largest constituent part During the last fifteen years, Pumphouse has grown in size from just over40animals, reaching a peak of114and then declining again to roughly50individuals as the result of the troop splitting into two daughter groups and changes in environmental conditions Pumphouse, like all baboon troops, is a cohesive unit with clear bound-aries separating it from other troops Individuals maintain contact with each other even when they are feeding and are dispersed over several miles Major subgroups exist within the larger troop, the most important of them being the family group For baboons this means a matriline (a female-cen-tered kin group) headed by a matriarch (the mother or oldest female in the

33 2

family) and including all descendant and collateral relatives Male offspring figure prominently in these matrilines until they leave their natal group at adolescence, so that all adult members of a family are females Paternity is difficult to assess because many males mate with a female in the cycle which she conceives The baboons generally act as if they do not recognize bio-logical paternity, but males become temporary members of a family group

on another basis (see below) Since families can include grandmothers and grandchildren and even great-grandchildren, when aunts, nieces, and the like are added in, a matriline can be quite large

All the troop's matrilines are ordered in a stable, linear dominance hierarchy Each family ranks above or below other families in such a way that even the smallest infant can use its family's status to make the adults

of a lower-ranking family give way Initially the reason is the intervention

of the mother or other relatives But by the time the youngster is about two years of age, this "dependent" rank becomes independent of such inter-vention The female hierarchy within the troop may in fact reflect the elabo-ration of the hierarchy which exists within a family In that hierarchy, the mother ranks at the top, with the youngest offspring just below her and so

on, according to increasing offspring age This counterintuitive system reflects the mother's willingness to intercede on behalf of her youngest against any

of her older children Sons fit into the female system until adolescence, when they forcibly push their way upward through the female dominance hierarchy (aided by the fact that they are now larger than any adult female) and rise in rank not only above their mother but above all females

The interactions among family members set the pattern for all friendly,

"affiliative" relationships Family members spend time together, feed, move, sleep, rest, play, and groom with each other The final important activity is defense When one individual gets into trouble and is threatened either by dangers from within the group or outside it, family members rush to give assistance

Family groups are tied together by friendships with nonfamily mem-bers (Strum 1975a, b).6 Friends resemble kin in that they are often in close proximity, feeding, resting, grooming, and defending each other Friend-ships can develop in many ways Young, unrelated females who grow up together as members of the same play group can form strong attachments that last into adulthood Young males make friends in the same way, but these ties end with adolescence

Adult males and most adolescent males in Pumphouse have come from some other troop They begin as strangers and eventually become integral members of the troop, yet when measured in terms of a female's lifetime, they are only temporary residents Males have friendships with females (sometimes the female initiates the friendship) and a male friend becomes

one of the family, albeit temporarily He often develops a strong tie with his female friend's youngest infant Acting more like a mother substitute than anything approaching the formalized Western idea of "father," he stays near the baby, grooms it, and protects it As the infant grows, he or she spends about half the day with the mother and the other half with his/her male friend(s)

The major exception to the rule of social attraction within the troop is between males Males, by virtue of their immigrant status, are normally strangers to each other The fear elicited by a stranger exaggerates the al-ready large personal space of male baboons In a few cases, males from the same troop may be in another troop together, but at least initially, they act like strangers rather than familiars

Unlike the males in previous baboon studies, Pumphouse males cannot

be ranked in a stable linear dominance hierarchy Relationships among males are basically dynamic, fueled to a great extent by male comings and goings The most important factor in understanding Pumphouse males appears to

be the length of time each male has resided with the troop For simple convenience I have identified four residency categories: "newcomers," whose tenure is less than one and a half years; "short-term residents," those between one and a half and three years of tenure; "long-term residents," whose tenure ranges between three and five years; and a recently created category of "longest residents" for those few males who have been with the troop longer than five years Males in each of these categories treat each other preferentially Males who are longer-term residents both fear new-comers and support each other against them, but that is the extent of their affiliation with each other Newcomer males are more aggressive7than resi-dents, and in the constant back and forth between males, newcomers win8 more of their encounters with residents than vice versa, although this situa-tion can change during one hour or one day As a result, male behavior is less predicted by stable dominance, based on various forms of aggression, than by the history of each of the males in the troop

All these intricate interactions and relationships exist by virtue of an elaborate communication system which is nonetheless severely restricted by comparison with humans Baboons use sounds, gestures, and postures to convey a range of signals, primarily expressions of the emotional state of the sender These communicate, for example, the following messages: I am up-set, I am excited, I am angry, and I am in conflict (when two sets of opposing emotions find expression at the same time) External reference is limited except that others, receiving this information about an individual's emotions, assess it within the current environmental and social context Within this system, all actions and all behaviors carry communicative potential Crucial

334

to our understanding of baboons is the observation that baboons commu-nicate through "behaving" rather than by talking about behaving

One final point will complete this brief overview Baboons are born relatively ignorant Although a baby baboon arrives in the world equipped

to cling tenaciously to his mother, roots and sucks with little difficulty, and finds contact with another baboon both necessary and rewarding, the baby

is certainly ignorant of the other basics of survival, such as what he should eat besides mother's milk or how to negotiate the social complexities of the troop All this learning occurs by observation and imitation, through play (where the lessons of adult life can be learned without serious punishments for mistakes), and sometimes through trial and error The mother is the first model and source of information; family members and friends, then play-mates, and finally the rest of the group provide the necessary additional information and experience

ANOMALIES

Why Are There Friendships?

A new male joins the troop His first approach is not an aggressive takeover but rather a period of quiet watching from the sidelines, sitting as close to group members as his "stranger" status will allow He does just what

a human observer of baboons does-determines the kinship and friendship structure of the troop and monitors troop interactions until he understands what is going on Then he acts But even at this point his actions are not to challenge the resident males He picks a female and begins to follow her, signaling friendly intentions while trying to approach The female is initially too frightened to let this stranger close, but his persistence, patience, the friendly sounds, gesture, and postures may finally win her over Her change

of "heart" is signaled by their first grooming session, during which the male grooms the female When she reciprocates, grooming him as well as letting him groom her, their friendship is truly under way Then the female follows the male, as much or more than vice versa, while he selects another female

to befriend in the same way, winning their initial acceptance into the troop through the females And all residents have strong friendships with females

We encounter problems when we try to interpret friendships within the traditional aggressive competition model From that perspective they are just "noise" in the system, what we might expect when many individuals live together for a long period But as will be seen, the Pumphouse data suggest that, rather than being superfluous socializing, friendships are an

integral part of the methods that baboons can use in competition and defense Let us consider competition first

A baboon group has several reproductively active males and a limited number of receptive females available at anyone time We should expect males to compete with each other for these females Yet in Pumphouse this competition takes an aggressive form in only 25 percent of the cases where one male gains possession of a female from another male (Strum 1982) In the majority of cases we find successful social maneuvers that rely on a male's social experience, his knowledge of his fellow group members, and hisfriendship with the contested female Fighting over a female does not,

in itself, guarantee reproductive success Female cooperation plays an im-portant role in whether a male can successfully face up to a challenger, and

a female also determines whether the male will be allowed to copulate An uncooperative female can tire her partner, disrupting both his feeding and his copulations These costs weigh heavily on the male, who may voluntarily abandon an uncooperative female In a sense, the female has won the right

to choose a male of her liking for her next consort partner The key to female cooperation appears to be the friendship that forms between males and females; females cooperate more with their male friends than with other males, and friendships become important aspects of male-male competition When a male aggressively challenges another male, we expect the defense to be Hight or fight Yet very often the threatened male baboon turns, instead, to a female (or an infant) to use as an agonistic buffer.9 Bolstered

by this unusual ally, the challenged male returns to face his opponent, often successfully averting further aggression The key to his success, however,

is the cooperation of his buffer Without it, the distressed male faces two problems (an aggressive opponent and a screaming liability, since the distress

of an uncooperative partner may bring the wrath of the troop upon the offender) instead of one Infant or female cooperation, here as in the case

of competition, correlates positively with friendship, and friendship becomes

an important aspect of male defense

We can now see why the first order of business for a newcomer male should be to form friendships with females and, through them, with infants

We can also observe that males without such friendships (newcomers during the early days of their residency) are at a disadvantage in both competing with and defending against males who have such ties Consequently, at least from the male's point ofview, friendships appear to be important investments that generate cooperative, predictable partners who can be used in social maneuvers during competition and defense Why females and infants should cooperate is discussed elsewhere (Strum 1983a, b) Basically, females and infants do not benefi t directly in the competitive and defensive interactions between males unless we consider grooming a benefi t Instead they reap

complementary benefits before and afterward: active assistance when under attack from conspecifics or external threats, access to limited resources that the male friend possesses, and a general decrease in interference from others when they are with the male friend Friendships create a delicately balanced system of social reciprocity in which each partner cooperates to the extent that he or she has benefited or hopes to benefit

Why Is There No Classic Male Dominance Hierarchy?

A new male joins the troop After he begins to befriend a female, he also begins to follow resident males, one at a time Continual following, harassment, and aggression by the newcomer occur regardless of what the resident might do Although resources can be involved, the "winning" new-comer does not claim his prize Often there is no resource in sight and the goal appears to be both an' assessment (Parker 1974) of the other male and

a method by which the resident is forced to recognize the newcomer's pres-ence in the troop The following ends as abruptly as it started, at a point where the resident and newcomer have reached some resolution of their relation-ship A similar sequence takes place between adolescent males maturing within the troop and the adult males already resident there (Strum 1982)

At the most basic level, the reason that there is no stable male domi-nance hierarchy in Pumphouse is that there is a constant influx and exit of males Because newcomers and maturing adolescents use aggression to "com-municate" with residents, to gain information about another male, and to force their recognition and ultimate acceQtance, the matority of male agon-istic interactions do not relate directly to competition Whatever traditional type of dominance hierarchy is extracted from these data loses its significance through the attempt to solidify what is basically a dynamic set of male in-teractions

When we look specifically at situations of competition over limited resources, for example receptive females and the meat on carcasses of prey that the baboons have captured (Strum 1975b, 1976a, b, c, 1981a), we find that even here aggression plays a somewhat minor role A good example is when males vie with each other over a sexually attractive female Friendships with females playa role in a male's success But other social maneuvers also operate to gain the female for a male For example, as tension mounts between a consort male and the other males following the consort pair, a change in partners can occur Often the new consort male is not one of the active followers but rather a male who had remained on the sidelines, un-noticed but closely monitoring the situation At the right moment, when the other males are involved with each other, he will rush to the female and claim her Similarly, he might incite other males against the consort