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University Level Course Syllabi

Sydney Perloe, Haverford College

      (Psychology, Biology, Sociology 221a)
      	Course Instructor
      	Sydney Perloe
      	Haverford College
      	Haverford, PA
      	Telephone: 1-610-896-1234
      	Fax: 1-610-896-1224
      	Average class size: 25
      Fall 1995 
      The syllabus is aimed at orienting you to the material that is
      assigned. Please read the relevant background material before
      going onto the actual assignment and use it to help you organize
      the information in the readings. You should have completed the
      readings by the meeting for which they were assigned. When
      assignments cover more than one meeting, try to complete the
      readings as early in the time period as you can.
      I. Introduction
      A. Primatology: history and orientation
      Our set of readings begins with a brief history and overview of the
      interdisciplinary field of primatology. Primatologists study
      prosimians, monkeys and apes at many levels ranging from genes and
      organismic process to primate "proto-cultures." The first
      selection by Hinde presents a framework that allows us to integrate
      phenomena from all of these levels. His hierarchical scheme
      composed of behaviors, interactions, relationships and structures,
      is used very widely. His second selection points to the linkage
      of physical and behavioral characteristics of interacting animals
      in adaptive complexes, that embody major strategic directions taken
      by the members of a species as they deal with the problems of
      adaptation. Both the bodily structure and the behavioral
      components of these complexes are affected by natural selection. 
      The excerpts from Dunbar present the four questions that comprise
      the evolutionary approach to the study of behavior. i.e., the
      questions of proximate cause (or mechanism), development (or
      ontogeny), function and evolutionary history. Each question can
      be asked about any behavior we wish to examine; answers to all
      four questions are required for a full explanation of any behavior. 
      Sept. 6
      1. Perloe, S. About primatology. pp. 1-4.
      2. Hinde, R. (Ed.) Primate Social Relationships. Preface,
      (through first paragraph on p. xi); Chap. 1, A conceptual
      framework, pp. xi-7. 
      3. Hinde, R. The Biological Basis of Human Behavior,
      Excerpt from Chap. 26, Adaptive differences in group
      structure, pp. 395-398.
      4. Dunbar, R. Primate Social Systems, Excerpt from Chap.
      1, Primates and their societies, pp. 1-9. 
      5. Burton, F. Non-human Primates. CD-ROM (on reserve). 
      Take a few minutes to familiarize yourself with this
      resource so that you can refer to it when we discuss
      particular species. It may also be helpful in selecting the
      species on which you want to report.
      B. Basic concepts and principles 
      We begin with the evolutionary orientation that guides current work
      on primate social systems. At this point our goal is to orient
      rather than to achieve mastery of the theory. The mastery goal
      will be approached slowly as we use the orientation to help us
      understand the everyday social lives of monkeys and apes and read
      more theoretical material throughout the semester.
      The two chapters by Barash provide a primer of modern Darwinian
      theory, that is, the theory of evolution by natural selection, and
      its application to the study of behavior. This is the perspective
      that guides primatology. Although Barash labels his approach
      sociobiology, the basic concepts he presents are also employed in
      behavioral ecology. The theory is most concerned with the function
      of behavior. The excerpts from Dunbar in this section give a more
      advanced treatment of the central, reproductive meaning of fitness
      and the difference between selection based on benefits to an
      organism's group and selection based on benefits to an organism's
      genes. He shows that fitness involves the solution of three
      problems, survival, reproduction and rearing offspring. The final
      part of the Dunbar selection discusses the various ways in which
      genes might influence behavior and the role played by genes,
      environment and an organism's decision processes in the
      determination of behavior.
      Sept. 8-11
      1. Barash, D. Sociobiology and Behavior, 2nd ed., Chap. 2,
      How it works; Evolution as a process, pp. 11-25; Chap. 3,
      Evolution and behavior; Getting it together, pp. 27-44. 
      Think about the answers to the study questions at the ends
      of the chapters.
      2. Dunbar, R. op.cit., Excerpt from Chap. 2, Theory of
      Reproductive Strategies. pp. 15-28.
      Sept. 10 ZOO TRIP (Details to be arranged.)
      Sept. 13 Quiz 1
      II. Baboons
      A. Savannah baboons
      Sept. 15-25 
      Savannah baboons, Papio anubis (olive baboons), Papio cynocephalus
      (yellow baboons) and Papio ursinus (chacma baboons) were the first
      primates to be studied at length in their natural habitats. The
      selection was based partly on their relevance to the search for a
      model of how primates evolved. Most live in the open, grassland
      settings that are believed to be the place in which the first
      hominids evolved. Savannah baboons were also chosen because it is
      easier to see and follow animals on open grasslands than in
      forests. Some savannah or common baboons, like the ones at Gombe,
      also live in the forest. The groups studied by Smuts and Strum
      lived in the more typical savannah setting. Despite the
      differences in the settings in which savannah baboons have been
      studied, their social structures are very similar. Later readings
      by Kummer and by Sugawara will describe some exceptions to this
      The groups examined in the Smuts and Strum readings were neighbors. 
      In fact some of the same animals appear in both studies. The books
      are rather different in style, one is closely tied to data that are
      presented along with the verbal descriptions and explanations. The
      other is a personal narrative account whose supporting data is not
      given. (It is given in a variety of journal articles and book
      Smuts provides us with an introduction to the species and her own
      study. Then we go to Strum's description of her personal
      introduction to the ~Pumphouse Gang~ and the introduction of a
      young transfer male.
      Although interactions among the males provide the most dramatic
      moments in baboon communities, it is the interactions and
      relationships among females and between females and their offspring
      that constitute the enduring core of baboon social organization so
      that this is where we move next. 
      Relationships among males and between males and females are then
      examined together because males usually interact with each other
      in the context of male-female interactions. We end with the
      puzzling relationships between males and infants and a
      consideration of the psychological mechanisms involved in
      friendships between males and females.
      1. Smuts, B., Sex and friendship in baboons. (Required
      text) Forward and Chaps. 1-3, pp. xi - 36.
      2. Strum, S., Almost human: a journey into the world of
      baboons. Chaps. 2-3, pp. 23-53.
      3. Smuts, op. cit. Chap. 7. pp. 123-156. (Note: You
      are not responsible for statistical details or procedures in
      this or any of the other chapters. You need to be able to
      describe the results in words, but you need not remember the
      exact numbers or understand the actual statistical
      4. Strum, op. cit. Chaps. 6-7, pp. 83-104. 
      5. Smuts, op. cit. Chaps 4-6, pp. 37- 122; Chaps. 8-9,
      pp. 159-234.
      II. Baboons
      B. Hamadryas baboons
      Hamadryas baboons (Papio hamadryas) live in very arid areas of
      Ethiopia and Saudi Arabia. Although they are very similar in
      appearance and basic individual behavior patterns to savannah
      baboons, they have a strikingly different social structure. They
      have not been studied as extensively as their common cousins,
      partly because of their inaccessibility and partly because most of
      them live in a region that was embroiled in war for many years. 
      Kummer's classic study gives us an overview of their social
      structure and of the interactions and relationships that make them
      different than savannah baboons. It also provides information
      about how hamadryas males and females develop their social behavior
      Sept. 27 
      1. Kummer, H. Excerpts from Social Organization of
      Hamadryas Baboons, Chap. 1, secs. 2-5, pp. 5-14, Chap. 4,
      pp. 29-83. (Read summary on pp. 81-83 before reading entire
      C. The source of the hamadryas - savannah difference
      Comparing savannah and hamadryas baboons allows us to deal with two
      questions: what is the evolutionary history of the hamadryas
      pattern and which dispositions seem to be most involved in the
      difference between the social structures in which the two species
      live. Baboons are unique in allowing us to see how small
      variations in dispositions can give rise to striking changes in
      social structures. The comparison also provides a good example of
      how dispositions interact with environmental settings to produce
      the social structures we observe. This understanding should help
      us when dealing with other primate species where the data are not
      as clear.
      Throughout a wide range of settings, e.g.,those at Gombe and at
      Gilgil, baboons have the social structure pattern described by
      Smuts ans Strum. This has led some, like Kummer, to describe their
      social systems, especially the male-female relationships aspect,
      as phylogenetic adaptations. He sees these patterns as adaptations
      whose form is narrowly constrained by genetic developmental
      programs. In contrast, he points to adaptive modifications, whose
      underlying programs lead to variations in response to varied
      environments. For example, baboons generally sleep in trees, but
      when trees are scarce, they sleep on steep rock formations. 
      Although Kummer dichotomizes adaptive behavior systems, it is
      likely that there are also evolved behavior systems that show
      intermediate degrees of flexibility. Evolved behavior systems that
      adjust, to a greater or lesser extent, to changes in settings are
      called facultative; those that operate the same way in all of the
      settings in which a species lives are called obligatory. Hamilton
      and Bulgar suggest that male-female relationships may be more
      facultative than Kummer believed. 
      It is important to recognize that facultative patterns do not vary
      arbitrarily, at the whim of the creatures involved. Rather they
      vary in a systematic way with variation in the environments in
      which they develop or operate. Much of behavioral science is aimed
      at discovering principles that describe the relationships between
      variations in environmental inputs to facultative behavior systems
      and the behaviors they produce. The distinction between obligatory
      and facultative patterns of behavior is very important for
      understanding human behavior from an evolutionary perspective. The
      environments in which virtually all humans live today are very
      different than the ones in which they evolved. Understanding the
      impact of this change requires that we recognize the extent to
      which our evolved adaptations are facultative and just how the
      flexible adaptations respond to particular environmental features. 
      This problem will be addressed directly in the next section,
      particularly in the selection by Tooby and Cosmides. 
      The contact between savannah and hamadryas baboons has given rise
      to hybrids whose behaviors provide still more information about the
      source of the differences in social structures of the two species. 
      The excerpts from Sugawara point to variation in male dispositions
      as the basis of the structural contrast.
      Sept. 29
      1. Kummer, H. Primate Societies. Chap. 5, How flexible is
      the trait?, pp. 131-142.
      2. Hamilton, W. and Bulgar, J. Facultative expression of
      behavioral differences between one-male and multimale
      savanna baboon troops. American J. Primatology, 28, 61-71.
      3. Sugawara, K. Excerpts from Sociological comparison
      between two wild troops of anubis-hamadryas hybrid baboons. 
      African Studies Monographs, 1982, 2, pp. 73-74, 120-122,
      III. The Evolution and Operation of Dispositional Adaptations
      Oct. 2-9
      A. Modules of the mind: the human language adaptation
      The most distinctive human adaptation is the use of vocal language. 
      We are disposed to learn and use language with a particular
      grammatical structure that is shared by all known human languages. 
      The chapter by Pinker, a psycholinguist, argues for recognizing
      the innate nature of the mechanism(s) that enables us to do what
      only humans can do, namely speak a language. He presents a simple
      scheme for understanding how innate mechanisms are affected by
      genes and environment as well as by the experiences we have that
      are themselves the consequences of innate mechanisms operating in
      an particular context. His model is very compatible with the one
      implicit in the four questions described by Dunbar, in Section I. 
      Pinker contrasts two views of the human mind. The first, the
      Standard Social Science Model, holds that humans have a single
      general learning mechanism that allows them to acquire all of their
      behavior patterns and that is equally open to acquiring any
      behavioral pattern our muscles and glands can produce. The second,
      the Modular view, proposes that we have a large number of specific
      behavior modules, each of which has evolved to deal with a
      particular adaptive problem. The modules vary in the extent to
      which they produce different outputs in different contexts. The
      best example we have of such modular functioning is in the learning
      and use of language. Pinker lists a variety of other possible,
      adaptive modules. Dispositions and modules refer to the same
      underlying brain mechanisms or structures that produce behaviors.
      1. Pinker, S. The language Instinct, Chap. 13, Mind design.
      pp. 404-430.
      B. Species-typical adaptations as "designs" for adaptive
      Tooby and Cosmides continue the examination of behavior generating
      brain mechanisms, which they call adaptations. They present a
      searching analysis of the distinction between general purpose
      behavioral mechanisms and ones that are designed to achieve
      specific, adaptive functions. Their discussion supports the view
      that evolution has resulted in a large number of specific
      mechanisms, each of which is designed to solve a narrow class of
      problems faced by organisms in the setting where the mechanism
      evolved. This historical context is called the environment of
      evolutionary adaptedness (EEA). Tooby and Cosmides criticize the
      correspondence view that evolution has resulted in a general,
      inclusive fitness maximizing mechanism, capable of generating
      adaptive responses in settings that are very different than the
      ones in which the mechanism evolved. The correspondence view is
      held by some primatologists who are behavioral ecologists, e.g.
      Dunbar. However, because these primatologists generally carry out
      their studies in natural settings that have changed little from the
      EEA, their findings do not necessarily support the existence of a
      general inclusive fitness maximizer. On the other hand, the two
      evolutionary approaches produce rather different expectations about
      the adaptedness of behavior in modern, human societies. 
      Tooby and Cosmides' treatment also elaborates Pinker's distinction
      between the environmental contribution to the development of a
      mechanism, i.e., ontogeny and the environmental inputs that
      stimulate the operation of a developed mechanism. Differences
      between present environments and the EEA can affect the current
      adaptiveness of an evolved adaptation through the impact on the
      adaptation's development or operation. Evolved adaptations that
      were very useful in the EEA may be quite maladaptive in modern
      1. Tooby, J. and Cosmides, L. Excerpts from The past
      explains the present: emotional adaptations and the
      structure of ancestral environments. Ethology and
      Sociobiology, 1990, 11, (read the sections within the
      following sets of page number ranges) 375-378, 384-387 (up
      to end of 1st. par.)388-389, 394-398, 399-402 . 
      C. Physiological mechanisms involved in the generation of
      species-typical social structures
      Both Pinker and Tooby and Cosmides deal with adaptive mechanisms
      or dispositions mainly on theoretical level. The next selection,
      by Mendoza and Mason, shifts the focus to some of the physiological
      systems involved in the operation of adaptive behavior mechanisms. 
      They identify some endocrine and autonomic nervous system
      correlates of species differences in social dispositions. The
      organismic systems they identify are probably "downstream" from the
      brain mechanisms that embody the dispositional adaptations. That
      is, they are probably monitoring the pathways through which the
      innate brain mechanisms involved in social adaptations actually
      generate behavior. Except for the studies of aphasia, described
      by Pinker, we know relatively little about the brain mechanisms
      involved in behavioral adaptations. It is very likely that they
      involve circuits in the limbic system, concerned with emotion, as
      well as in the frontal cortex, concerned with integrating and
      planning action. Both of these parts of the brain influence the
      physiological systems discussed by Mendoza and Mason.
      1. Mendoza, S. and Mason, W. Constitution and context: the
      social modulation of temperament. In J.J. Roeder et al.
      (Eds.) Current Primatology, Vol. II. pp. 251-256.
      IV. Behavioral Ecology
      Earlier, we described two approaches to primatology, sociobiology
      and behavioral ecology. While the two share a basic evolutionary
      orientation, sociobiologists focus on the impact of social
      strategies on behaviors closely related to reproduction, e.g.
      competition for mates, acquiring and maintaining dominance ranks,
      and incest avoidance. The alternative approach focuses on
      strategies oriented toward getting food and protection against
      predators. As a result, behavioral ecologists pay a great deal of
      attention to the ecological setting in which a group lives in order
      to discover what kinds of food are available and how these
      resources are distributed in space and over time. Our examination
      of baboons included information from both approaches, but depended
      most heavily on sociobiological analyses. In this unit we will
      emphasize behavioral ecology.
      Oct. 11-13
      A. The Behavioral Ecology and Social System of Squirrel
      Our introduction to behavioral ecology comes through the work of
      Dr. Sue Boinski, a biological anthropologist, who has studied new
      world monkeys, especially squirrel monkeys. The cat sized, squirrel
      monkey is one of the most common monkeys in South and Central
      America. It is an extremely active animal that runs about through
      the middle and higher levels of trees in the forest. Despite its
      ubiquity, its size, speed and habitat make it difficult to study
      in the wild. Most of what we know about squirrel monkeys comes
      from studies of groups in captivity. Dr. Boinski is one of the few
      primatologists who have done long term studies of squirrel monkeys
      in their natural habitats. 
      We can describe squirrel monkey behavior and interaction patterns
      in considerable detail, but there is more uncertainty about the
      relationships and social structure of the one or more species in
      this genus. These relationships vary considerably between the
      mating and birth seasons. During the most of the year, males and
      females have little to do with each other. Although the males
      sometimes fight each other furiously, they also seem to have close
      affiliative relationships. Squirrel monkeys have some curious,
      genital display patterns that are involved in agonistic and
      affiliative relationships. Because they are small and easy to
      maintain, squirrel monkeys have been a favored laboratory research
      animal. There has been considerable work on brain and other
      physiological components of squirrel monkey behavior patterns. 
      The first paper in the set points to the likely impact of
      predation pressure and seasonal fluctions in food abundance in
      determining the narrow window during which squirrel monkey females
      give birth. The next item in the set, by Janson and Boinski, 
      deals with how a species~ bodily characteristics, e.g., size, and
      its behavior patterns contribute to its ability to exploit
      potential food resources in its environment. Boinski and Timm
      provide an example of such exploitation in a paper about how
      monkeys (and predatory birds) are able to get at a particular
      species of bat. 
      The last two papers in the set move beyond specifically ecological
      concerns. One deals with the way female vocalizations allow
      squirrel monkeys to keep in touch as they forage through the dense
      foliage of trees. The other looks at male squirrel monkey mating
      1. Be sure to browse the New World Monkey section of the
      Burton CD-ROM before you begin reading the items sent by Dr.
      2. Boinski, S. Birth synchrony in squirrel monkeys
      (Saimiri oerstedi). Behavioral Ecology and Sociobiology,
      1987, 21, 393-400.
      Optional reading
      3. Janson, C. and Boinksi, S. Morphological and behavioral
      adaptations for foraging in generalist primates: the case of
      the cebines. American J. of Physical Anthropology, 1992,
      88, 483-498.
      4. Boinski, S. and Timm, R. Predation by squirrel monkeys
      and double-toothed kites on tent-making bats. American J.
      of Primatology, 1985, 9, 121-127. 
      5. Boinski, S. The coordination of spatial position: a
      field study of the vocal behavior of adult female squirrel
      monkeys. Animal Behavior, 1992, 41, 89-102. 
      6. Boinski, S. Mating patterns in squirrel monkeys (Saimiri
      oerstedi): implications for seasonal sexual dimorphism. 
      Behavioral Eco;ogy and Sociobiology, 1987, 21, 13-21. 
      Oct. 18
      B. The Evolution of Group Living
      With very few exceptions, primates live in organized groups. 
      While it is easy to conceive of the benefits of group living,
      it is important to recognize that this mode of life also
      carries costs. The costs are high enough to raise the
      question of why primates are such gregarious animals, that is,
      which selective pressures gave group living animals sufficient
      benefits to outweigh the costs of group life. A related, but
      separate, question arises in response to the enormous
      variations among species in the structures of their societies. 
      Which selective pressures lead each species to develop its
      species characteristic form of society? 
      Behavioral ecologists have been particularly interested in
      these questions. Wrangham's paper presents a very influential
      hypothesis about the ecological setting that made female
      bonded social structures, so common among terrestrial and
      semi-terrestrial species. He was among the first to recognize
      that the evolution of a species' social structure depends
      primarily on what helps females, in a particular ecological
      setting, gain a competitive advantage in access to food . The
      spatial distribution of food is the aspect of the setting that
      is critical in shaping female social relationships. If the
      distribution gives one pattern of social organization among
      females a clear advantage over others, males will adapt to
      that pattern. 
      VanSchaik revises and extends Wrangham's hypothesis. First
      he notes that there are two forms that competition over a
      resource can take, scramble competition and contest
      competition. He also examines the separate effect of
      competition between females belonging to the same group and
      between females belonging to different groups. In contrast
      to Wrangham, VanSchaik believes the the distribution of food
      does not influence whether animals evolve a gregarious, as
      opposed to an independent living strategy. He holds that the
      selection of group living occurs in response to predation
      1. Wrangham, R. W. Ultimate factors determining social 
      Structure In R. Hinde (ed.), Primate Social Relationships. 
      pp. 255-262.
      2. Van Schaik, C. Excerpts from "The ecology of social
      relationships amongst female primates." In V. Standen and
      R. Foley, (eds.), Comparative socioecology: the behavioral
      ecology of humans and other mammals., pp. 195-217.
      Oct. 20 Review and Catch up
      Oct. 23 Midterm
      V. Macaques
      Macaques are the most widespread non-human primate genus, ranging
      from Morocco and Gibralter in the west to Japan in the east and
      from the tropical rain forests of Indonesia to the winter snows of
      Japan. They are primarily forest living, but have adapted very
      well to living alongside humans. The selections from Fedigan and
      deWaal describe general aspects of the two most studied species,
      rhesus (Macaca mulatta) and Japanese (Macaca fuscata) macaques. 
      These species, along with the crab-eating (M. fascicularis) and
      pigtailed (M. nemestrina) macaques have fairly similar social
      structures. However, there are some species, e.g., the barbary (M.
      sylvanus), bonnet (M. radiata) and stumptail (M. arctoides)
      macaques that differ from the familiar macaque pattern. The Burton
      CD-ROM provides information about the many other macaque species. 
      While you are not expected to remember the names or details about
      every one of the macaque species, you should have an idea of the
      extent of their distribution and the kinds of similarities and
      differences that are found among them. We will rely on class
      reports for part of our coverage of macaques.
      The rhesus/Japanese macaque social structure epitomizes the female
      bonded pattern described by Wrangham. Because the most central
      features of such societies are the kinship and rank relations among
      females, we begin our detailed examination of these societies with
      a study of the routes through which females acquire and maintain
      their ranks. Chapais has done the most important experimental
      studies of these processes. These studies grew out of earlier
      field research. He was a Philips Lecturer at Haverford last year
      and presented two talks about his work and about rank related
      behavior among female macaques. Tapes of these are on reserve in
      Magill Library as is the edited set of excerpts from the talks.
      Oct. 25-30 
      A. Japanese and Rhesus macaques (Background)
      1. Fedigan, L. Primate paradigms, Ch. 14, a section on
      Japanese Macaques, pp. 218-223. 
      2. deWaal, F. Peacemaking Among Primates. Excerpts from
      Chap. 3, Rhesus Monkeys, pp. 89-104.
      B. Kinship and Rank
      1. Chapais, B. and LaRose, F. Experimental rank reversals
      among peers in Macaca fuscata: Rank is maintained after
      removal of kin support. American J. Primatology, 1988, 16,
      2. Chapais, B. Selections from videotaped talks, November,
      1994. (On reserve.)
      C. Migration and group splitting
      1. Perloe, S. Joining a group on Cayo Santiago: a case
      study. (American Society of Primatologists, 1993.)
      D. Macaque Reports
      VI. Conflict, Cooperation and Reconciliation
      Nov. 1
      A. Dominance
      Two fundamental aspects of social life in any primate species
      are conflict and cooperation. Much of our examination of the
      social systems of baboons and macaques was concerned with
      these processes so that the concepts examined here are already
      familiar. However their central importance justifies
      additional attention. The aspect of social conflict that has
      been studied most intensively is dominance, a relationship
      between two animals in which one reliably yields to another
      when the possibility of conflict between them arises. It is
      essential to recognize that dominance is not a feature of an
      individual animal, but a feature of a relationship between
      animals. The same animals can be dominant in some
      relationships and subordinate in others. In many primate
      societies, dominance relationships are patterned
      hierarchically, that is, when A is dominant to B, A is also
      dominant to all animals that are subordinate to B. An
      animal's place in a hierarchical dominance structure is often
      referred to as its rank.
      The evolutionary perspective focuses on four sets of questions
      about dominance relationships: 
      Function. What do the partners in the relationship get
      out of it (in both the short and long term)? 
      Mechanism. Which psychological processes make an animal
      behave in a dominant or subordinate way in a
      Development. What events in the life experiences of an
      animal affect its rank? How do animals acquire their
      Evolution. The major question asked here is about the
      relationship between ranking systems among non-human
      primates and human ranking systems based on power and
      DeWaal describes the interactions involved in dominance
      relationships and some of the confusions that have arisen in
      attempts to measure dominance. He points out that both parties
      benefit from dominance relationships and shows that dominance
      relationships are linked to cooperation as well as conflict. 
      Although his major concern is with the description of dominance
      relationships and their relatively short term functions, deWaal's
      discussion of a possible dominance drive also touches on the
      mechanism question. We will discuss this question more fully in
      Walters and Seyfarth's discussion of cooperation, conflict and
      dominance is more broadly focussed than deWaal's. They deal with
      the development and long term functions of dominance relationships
      as well as with patterns of affiliative relationships, especially
      those involving grooming. Both grooming and dominance related
      interactions seem to involve mechanisms that produce social
      relationships rather than immediate material benefits to the
      participants. The excerpt from Silk's chapter is concerned with
      the long term functions of dominance rank. She identifies what
      theory leads us to expect about functions and indicates problems
      in assessing whther these functions are actually served by
      attaining high rank.
      1. deWaal, F. Dynamics of Social Relationships. In Smuts,
      B. et. al., (Eds.) op. cit., Chap. 34, pp. 421-429.
      2. Walters, J. R. & Seyfarth, R. M. Conflict and
      Cooperation. In Smuts, B. et. al., (Eds.) op. cit.,, Chap.
      25, pp. 306-317.
      3. Silk, J. Excerpt from Social Behavior in Evolutionary
      Perspective . In Smuts, B. et. al., (Eds.) op. cit., Chap.
      27, pp. 318-324.
      Nov. 3
      B. Reconciliation
      Contrary to everyday understanding, conflict and cooperation are
      closely linked social processes; animals cooperate in order to
      compete more effectively. Because of the nested structure of
      primate societies, where individuals are linked into relationships,
      that are in turn linked into broader relationships, lines of
      conflict must often be bridged to form higher level alliances. 
      DeWaal has been the main researcher to identify reconciliation and
      to discuss the part it plays in the maintenance of primate social
      systems. He notes that reconciliation simultaneously reinforces
      dominance relationships and facilitates cooperation between
      dominant and subordinate partners. The two sets of excerpts
      illustrate species differences in reconciliation. They are written
      in a popular way, but they are based on research that has been
      published in a fully documented format.
      1. deWaal, F. Peacemaking among Primates. Excerpts from
      Chap. 3, Rhesus monkeys, pp. 110-122, and Chap 4, Stumptail
      monkeys, pp. 154-163.
      VII. Gelada Report
      We now move away from the heavily studied macaque and papio
      (baboon) genera in order to get a fuller view of the variety of
      social systems generated by primates. While all of these systems
      result from the operation of the same set of evolutionary processes
      operating on varied phyologenetic lines in varied settings, we will
      want to be sensitive to the surface differences as well as to the
      underlying continuities across primate era. The background
      readings provide either a brief overview or a sample of research
      on a species. Try to identify the major forms of relationships and
      structures in each of the species and to think about the conditions
      that might have led each species to evolve as it did. Be sure to
      browse the Burton CD-ROM for each of the species covered. 
      The first ~novel~ species we consider is geladas. Although they
      are often referred to as baboons and live in a habitat that
      overlaps the one occupied by some baboons, they are not classified
      in the same genus as baboons and they utilize the habitat quite
      differently. Despite the similarity between hamadryas and gelada
      social structures, i.e., one male units that form larger bands, 
      the structures grow out of different patterns of relationships. 
      Nov. 6 
      1. Fedigan, L. Excerpt from Primate Patterns, Chap. 15, pp.
      VIII. Langur Reports
      Most species of langurs are forest dwelling, arboreal animals, but
      the hanuman langurs described by Hrdy live in mixed forest and
      scrub near an Indian town and spend much of their time on the
      ground. The general form of social organization, namely, small,
      one-male, bisexual groups and small, all-male groups seems common
      throughout the genus. At one time there was much controversy over
      the pattern of males taking over bisexual groups by ousting the
      resident male and then killing unweaned infants. Some believed
      that it was a peculiarity bred by the overcrowding and
      disorganization found among monkeys living near humans. Although
      the pattern is less frequent in some settings than in others, it
      has now been found in uncrowded groups living far from humans as
      well as in ones like those studied by Hrdy. Hanuman langurs have
      several other unusual patterns, besides infanticide, that
      distinguish them from species we have studied. For example, female
      kin have close relationships with each other, but they do not form
      female bonded societies or strong ranking systems and infants spend
      unusual amounts of time awy from their mothers, even on the first
      day of life.
      Nov. 8 
      1. Hrdy, S. Infanticide as a primate reproductive
      strategy. American Scientist, 1977, 65, pp. 40-49. 
      IX. More New World Monkeys Reports
      About 35 million years ago, South America was a large island, lying
      much closer to the coast of Africa than it does today. It was a
      time at which earlier prosimian forms were beginning to give rise
      to the anthropoid radiation of monkeys and apes. Some of the
      monkey-like forms reached South America on tectonic islands that
      broke away from the African land mass and drifted across the narrow
      South Atlantic. These trans-Atlantic voyagers were the ancesters
      of modern new world monkeys. Although they resemble each other in
      many ways, old and new world monkeys have evolved separately since
      the initial migration of ancestral forms. 
      The two sets of monkey families are most easily distinguished by
      the shapes of their noses. Old world monkeys have downwardly
      pointed nostrils that are side by side, as in humans; new world
      monkey nostrils open to the side and are spaced apart from each
      other. A few species of new world monkeys also have prehensile
      tails that function as fifth limbs and aid the animals in moving
      and feeding in the trees. 
      All new world monkeys live in the trees all or almost all of the
      time. This is a dramatic change from most of the old world monkeys
      we have studied. The distribution of food and the dangers of
      predation are different for tree living than for ground living
      monkeys. Some of the differences in social systems between the two
      sets of animals can be traced to differences in the ecological
      settings in which they live. 
      Nov. 10
      A. Muriqui (Wooley Spider Monkeys)
      Muriqui are among the largest new world monkeys. Most of what we
      know about them comes from the studies of Karen Strier (a
      Swarthmore grad). Someone who thought that all monkeys were like
      baboons and rhesus macaques would be confounded by the muriqui. 
      Neither males nor females seem to develop dominance relationships. 
      Aggression is extremely rare within groups (perhaps not between
      groups). Females migrate and males generally stay in their natal
      groups. The differences between baboons and macaques, on the one
      hand, and species like muriqui, on the other, challenge us to
      understand the origins of variation in primate social systems. We
      will discuss the implications of this variation for understanding
      human evolution at the end of the semester.
      1. Strier, K. New world primates, new frontiers: Insights
      from the wooley spider monkey, or muriqui (Brachyteles
      arachnoides). International J. Primatology, 1990, 11, 7-
      B. Howler Monkeys
      Howler monkeys have the distinction of being the subjects of the
      very first scientific field study of primate behavior (Clarence
      Carpenter's 1934 study of the Barro Colorado Howlers). Because
      they are large, noisy and slow moving they have been the subject
      of many studies, despite the fact that they often live very high
      in the trees in very dense rain forests. It is difficult to
      identify the major relationships that hold howler groups together. 
      They are certainly not female bonded like many macaques and
      baboons, nor do they seem to have particularly strong relationships
      among males or even between males and females. Some features of
      their social structure resemble the ones seen among langurs, but
      others do not. The paper by Crockett focuses on the problems in
      understanding howler females, but aspects of male behavior are
      equally problematic.
      1. Crockett, C. Family feuds. Natural History, 1984, 93
      (8), pp. 54-62.
      X. Ape Reports
      The first representatives of the hominoid family of primates
      (humans, great apes and lesser apes) first appeared in the fossil
      record about 20 million years ago. Modern hominoids are tailess,
      have shoulder joints that permit a much greater range of arm
      movement and hip joints that permit a much greater degree of leg
      extension than is true of monkeys. These were probably adaptations
      that helped apes move through trees and feed while hanging from
      branches, rather than by walking on branches, as monkeys usually
      do. The skeletal modifications also served as preadaptations for
      upright posture and bipedalism, that were so important in the
      evolution of the hominid subfamily. (Humans are the only living
      hominids.). They are also characterized by proportionately larger
      brains and longer periods of immaturity than is found among
      Each of the living ape genera has a very distinctive form of social
      organization. Some ape social systems, such as those of
      chimpanzees and bonobos are extremely complex; others, like those
      of orangutans, are very simple. Despite their variation, all share
      the absence of female bonded social systems. While females have
      very close relationships with their immature offspring and
      sometimes their mature offspring, they do not have long term
      relationships with adult sisters, cousins, neices, grandaughters,
      etc. . This is linked to the fact that among all ape genera, most
      females leave the social units into which they are born. Among
      chimpanzees, bonobos and occasionally gorillas, males stay in their
      natal units. 
      Primatologists are interested in apes for two reasons; first, they
      provide information about the diverse ways in which primates can
      solve adaptive problems and (like all other categories of animals). 
      That is, they provide data about general socio-ecological
      principles. Second, they are our closest living relatives. 
      Chimpanzees and humans may have shared a common ancestor as
      recently as 5 million years ago. Some primatologists believe that
      this close relationship allows us to use aspects of modern ape
      social systems to model the kind of system in which pre-human
      hominids lived. (See XII. B., below.) The social system of early
      hominids was a crucial part of the EEA (See III. B., above) in
      which the social dispositions of modern humans evolved.
      We will discuss this possibility at the end of the course. For
      now, we will concentrate on understanding the modern ape societies.
      Nov. 13
      A. Gibbons and Siamangs 
      The lesser apes have fairly similar social systems and are among
      the few monogamous primates (Several new world species, including
      the titi monkey, are also monogamous.) Despite living together for
      most of their adult lives, gibbons and siamangs would not make very
      good subjects for romantic novels. They do help us to identify the
      circumstances that make monogamy an adaptive pattern and to
      identify processes, other than emotional attachment that can
      produce the pattern. (In contrast, titi monogamy does appear to
      involve a strong emotional attachment. See III. C., above.)
      1. Leighton, D. Excerpt from Gibbons: territoriality and
      monogamy. In Smuts, B. et al., (eds.) op. cit., pp. 135-
      B. Orangutans
      Orangutans present many puzzles. They are very large and ungainly,
      yet they live high in the trees where they have difficulty moving
      about. Skeletons of orangutans show evidence of many healed broken
      bones, most likely caused by falls. In captivity, they are very
      capable learners, but their behavior in the wild shows little
      evidence of either great social or material intelligence. They
      belong to an animal family noted for the complexity of its social
      systems, but they appear to live an almost asocial existence. Part
      of the confusion may stem from our knowing so little about them. 
      They live high in the trees in very inaccessible areas, that are
      being destroyed very rapidly by logging. 
      1. Rodman, P. and Mitani, J. Excerpt from Orangutans:
      sexual dimorphism in a solitary species. In Smuts, B. et
      al., (eds.) op. cit., pp. 146-150.
      Nov. 15
      C. Gorillas
      Gorillas present still another variant of the one-male group social
      structure. While most of the detailed information we have about
      the species come from the long term studies of mountain gorillas
      begun by Dian Fossey, the general form of gorilla social structure
      appears to be common to groups living in other areas. Gorillas
      have very large intestines that allow large amounts of leafy matter
      to be digested slowly. The pointed shape of gorilla heads is due
      to powerful jaw muscles that arch over the skull and give gorillas
      the ability to chew very coarse vegetation. These adaptations
      permit gorillas to extract much of their nutrition from very low
      quality food, that is very abundant. A typical one-male group need
      not travel very far to the food it needs, but its members do have
      to spend a lot of time eating and digesting. 
      Most of the time gorillas eat and rest peacefully, but occasionally
      there are very violent encounters between groups or between lone
      males and groups. A male sometimes bites so strongly that he
      buries his canine teeth in the skull of his opponent. Lone males
      sometimes attack females and kill their infants. The dominant
      silverback (fully mature males have grey hair on their backs) is
      generally very tolerant and protective of immature group members,
      most of whom are likely to be his offspring. Relationships between
      the silverback and adult female group members are generally
      relaxed, while those among the adult females are distant or mildly
      1. Stewart, K. and Harcourt, A. Excerpt from Gorillas:
      Variation in female relationships. In Smuts, B. et al.,
      (eds.) op. cit., pp.155-160.
      XI. Chimpanzees
      Chimpanzees have the most complicated social system yet encountered
      among non-human primates. It is characterized by shifting sub-
      groupings of individuals belonging to a larger community. The
      confusing pattern of coming and going at first led primatologists
      to think that chimpanzees had completely open societies, in which
      animals could join and leave groups freely. They also seemed to be
      remarkably relaxed about mating, with males apparantly uncompetitve
      about sharing mating opportunities with estrous females and females
      ready to mate with all interested males. However, the long term
      (over 25 years) studies of Japanese researchers and Anglo-American
      researchers at two sites along Lake Tangyanika, revealed that there
      were group boundaries and that there was competition among males
      and among females in a single community as well as between groups.
      Nov. 20
      A. Field studies
      The overview chapter by Nishida and Hiraiwa-Hasegawa describes the
      general features of chimpanzees in the context of a comparison of
      chimpanzees and bonobos. We will deal with the comparison when we
      discuss bonobos. The best known chimpanzee researcher is Jane
      Goodall. We have assigned only parts of one chapter of her book
      about more than two decades of research at Gombe. Her writing
      presents exceptionally rich portrayals of individual animals as
      well of the patterns of interactions and relationships that
      characterize the community. 
      1. Nishida, T. and Hiraigawa-Hasegawa, M. Excerpt from 
      Chimpanzees and bonobos: cooperative relationships among
      males. In Smuts, B. et al., (eds.) op. cit., pp.165-
      172, 174-180. .
      2. Goodall, J. Excerpts from The Chimpanzees of Gombe,
      Chap. 7, A Unique Society, pp. 146-159, 166-171.
      Nov. 22-29 (Have a Nice Thanksgiving Holiday , Nov.24-26)
      B. The Arnhem zoo study 
      The deWaal book, Chimpanzee Politics, deals with a captive group
      whose demographic structure is very different than that of a
      natural chimpanzee community. Despite this difference, the
      patterns he describes are extremely similar to those described by
      Goodall, except for relationships among adult females and, perhaps,
      for the part played by adult females in the changing dominance
      relations among adult males. Make an effort to connect the
      information derived from the two settings in which chimpanzees have
      been studied.
      1. deWaal, F. Primate Politics, Chaps. 1 - 5, pp. 53-
      XII. Bonobos
      Bonobos are the most recently recognized species of ape. They
      belong to the same genus as chimpanzees (Pan), whom they resemble
      in many ways. To some extent, they have replaced the 1960's view
      of chimpanzees as the focus of the desire for a peaceful, sexy
      model of what we wish our ancestors might have been, viz. a
      primate living in golden age of joyous innocence before the fall
      into hominid self-consciousness. The excerpt from DeWaal's chapter
      on a captive group describes some of the behavior patterns that
      make bonobos so interesting. The remainder of the chapter by
      Nishida and Hirai-Hasegawa provides information from the studies
      of wild groups. Just as was true of chimpanzees, it is likely that
      we will not understand the basic features of bonobo social
      structure until they have been studied for many years
      Dec. 1-4
      1. DeWaal, F. Peacemaking Among Primates. Excerpts from
      Chap. 5, Bonobos, pp. 170-182.
      2. Nishida, T. and Hiraigawa-Hasegawa, M. Excerpt from
      Chimpanzees and bonobos: cooperative relationships among
      males. In Smuts, B. et al., (eds.) op. cit., pp.172-174
      (also review parts of chapter read earlier).
      XIII. Implications of Nonhuman Primate Behavior for Hominid
      Dec. 6 
      A. Cognitive mechanisms of social behavior
      As we saw in section III of the course, the evolutionary approach
      requires us to examine the mechanisms that produce the patterns of
      behavior out of which social systems are constructed. It also
      requires us to discover the way we take on the patterns as we
      develop in the course of our individual lives. 
      The interest in the mechanisms generating adapative behavior in
      non-human primates, as well as in other animals is probably the
      oldest one in the evolutionary approach. It was important to
      Darwin and was central to psychology in the decades around the turn
      of the century. At that time, animal researchers were concerned
      with how animals thought. (Kohler's book about chimpanzee problem
      solving was called "The Mental Life of Apes.") Researchers assumed
      that adaptive patterns were the product of cognitive processes,
      that is, processes involved in gathering, remembering and
      interpreting information. 
      The behaviorist movement (1920-1960) pushed the concern with
      cognitive mechanisms aside. Animal psychologists turned to
      studying conditioning and the effects of various nervous system
      and endocrine system structures on behavior. These studies, which
      continue today, have contributed to our knowledge of the
      motivational-emotional mechanisms that generate social behavior. 
      Information about both cognitive and motivational-emotional
      mechanisms is necessary for understanding the way adaptive behavior
      patterns are produced.
      The return of cognition to center stage in psychology was followed
      by a resurgence of interest in the mental lives of non-humans,
      especially monkeys and apes. We began to look for cognitive
      mechanisms that allowed nonhuman primates to participate in complex
      social systems. Studies, like those described in the chapter by
      Cheney and Seyfarth, demonstrated that monkeys and apes had a more
      sophisticated understanding of their social environments than one
      might expect, given their lack of language. Some primatologists
      believe that the apparant use of deception by monkeys and apes
      means that they even have some rudimentary understanding of the
      mental lives of their fellow creatures as well as of their social
      1. Cheney, D and Seyfarth, R. How Monkeys See the World,
      Chap. 3, pp. 58-97.
      Dec. 8
      B. Conceptual vs. referential models 
      Tooby and DeVore describe two ways in which information about non-
      human primate societies can enrich our understanding of the
      influence of evolution on hominid, and ultimately, specifically
      human social systems. The referential approach uses existing
      nonhuman primate species to create a model of what our ancestral
      hominid species were like and by extension what directive
      influences evolution has exerted on the development of human social
      systems. The conceptual approach uses existing nonhuman primate
      species (and animal species in other orders as well) to generate
      two classes of theoretical propositions. The first class,
      socioecological principles, identifies relationships between
      aspects of social structure and aspects of the setting in which the
      structure evolves. An example of this would be Wrangham's
      principle that points to a relationship between the presences of
      clumped food resources and the development of female bonded
      societies. The second class, sociobiological principles,
      identifies relationships between different aspects of social
      systems. An example of this would be the relationship between
      mating patterns that promote certainty about paternity and the
      presence of paternal care. 
      Tooby and DeVore call their particular conceptual model a strategic
      model because it treats behavior as the product of strategies that
      have evolved to maintain or increase organisms' reproductive
      success. This approach, central to modern primatology, is the one
      we have taken. Part of the chapter (Strategic Modeling) was
      omitted because it deals with ideas we discussed earlier in the
      semester. However it can be reviewed as a useful, advanced summary
      of the approach.
      Relying on socioecological and sociobiological principles, Tooby
      and DeVore believe that we can use information about the
      environment in which hominids originated (the hominid EEA) to
      generate propositions about the social systems they would have
      evolved. Information about the hominid EEA specifies the values
      of the parameters in the socioecological principles. Once the
      parameters are known, we can enter them into the principles in
      order to specify some aspects of hominid social sytems. The
      sociobiological principles can then be used to infer additional
      features of the social systems entailed by the features specified
      by socioecological principles.
      It is hard to disagree with the conceptual approach. The problem,
      as noted by Wrangham and others, is that we are far from having a
      body of either socioecologiocal or sociobiological principles that
      is sufficient to accomplish the goals set out by Tooby and DeVore. 
      The Tooby and DeVore paper is merely an illustration of how a
      conceptual model might be developed and applied and a critique of
      existing models, rather that a full description and application of
      the model.
      Wrangham's paper is far more modest. It recognizes that no single
      species of non-human primate can serve as a model for our earliest
      hominid ancestors. He builds on the paleological principle that
      features common to many members of closely related species are
      usually ones that were present in the common ancestor of the
      species. He calls these an ancestral suite of features. They are
      ones that have been conserved over the course of evolution and are
      therefore likely to be basic aspects of the adaptive patterns
      characterizing a whole family of genera. Wrangham attempts to
      identify the ancestral suite present in the common ancestors of
      hominids and apes and therefore likely to be at the core of the
      adaptative social patterns humans received from their ancestors.
      While the conceptual and referential approaches differ, they are
      not incompatible. They should yield overlapping descriptions of
      the evolved social patterns that were available to our ancestors
      as they began to be human and enrich their social strategies
      through reliance on culture.
      B. Conceptual and referential models 
      1. Tooby, J. and DeVore, I. Excerpts from The
      reconstruction of hominid behavioral evolution through
      strategic modeling. From W.G. Kinzey, (Ed.) The Evolution
      of Human Behavior: Primate Models, (read the sections within
      the following sets of page number ranges) pp. 183-190, 200-
      202, 207-215, 222-226, 235-237. There is also an optional
      section, pp. 190-199.
      Optional Reading 
      2. Wrangham, R. W., ~African apes: The significance of
      African apes for reconstructing human social evolution.~ 
      From W.G. Kinzey, (ed.) op. cit. pp. 51-71. 
      Dec. 11 Summary
      Term Papers are due.