Chapter 5 Outline

Introduction

• The dramatic episode of the Ebola virus in 2014 serves as a tangible reminder of the close relationship between the great apes and our species, and they exist because of the extensive evolutionary history we share as primates. These connections and similarities interest biological anthropologists, who study human biological adaptations, variability, and evolution in the context of human culture and behavior. Biological anthropology encompasses the study of primates with a goal of identifying what in human behavior is general to primates, what is restricted to a few kinds of primates and humans, and what is uniquely human.
• Central to biological anthropology’s interest in living primates is the question, what can studying other living primates tell us about what it means to be human? Embedded in this larger question are the following problems:
• What does it mean to be a primate, and why does it matter to anthropology?
• What are the basic patterns of primate behavioral diversity, and under what conditions did they develop?
• How do behavior patterns among monkeys and apes compare with humans?
• What can studying monkey and apes really illustrate about human distinctiveness?
• Within our distinctive evolutionary trajectories, there is a wide array of possibilities involved in being a primate and no single primate provides a totally adequate model for human evolution or behavior.

What Does It Mean To Be A Primate, And Why Does It Matter To Anthropology?

• Similarities between monkeys, apes, and humans have been recognized, celebrated, condemned, and puzzled over for a long time. Linnaeus formalized those similarities for science, classifying humans along with other apes and monkeys. His taxonomy placed humans in the genus Homo along with chimpanzees and orangutans.
• These were the only other large apes known to European scientists at the time. He placed Homo in a family he called Primates, and also included Simians and Lemurs.
• Later scientists refined this taxonomy. That Linnaeus slotted humans into his system is both important as well as controversial. Darwin faced this controversy when critics charged that his theory of natural selection communicated that humans evolved from monkeys. Humans are not monkeys, nor did we evolve from them. But monkeys and humans are both primates.
• The word “primate,” derived from the Latin word for “of the first rank,” implies that these creatures are a higher order than other life forms.
• Primates are social mammals with grasping hands, bony and enclosed eye sockets, and relatively large brains. They share a common ancestry that split from other mammals some 65 million years ago, and live in mostly tropical and subtropical areas of the Americas, Africa, and Asia.
• The most important things that define what it means to be a primate are manual dexterity and visual acuity. Being adept and skillful with the hands, and in many cases, feet. Having five individually moveable fingers involving an opposable thumb, as well as large toes, allows for fine movements. Primates are able to live in a wide variety of environments and make use of many different resources, which manual dexterity supports.
• Primates have excellent vision, and are not as reliant on smell as other animals. Their eyes face forward and are close together, and each eye captures its own information, creating stereoscopic vision, or three-dimensional vision with depth perception.
• Other shared characteristics include general intelligence, which is related to a larger brain size, locomotive flexibility and a collarbone which provide greater mobility, and longer gestation times and childhoods which often involves training to live in complex social groups.
• Primates vary among themselves, sometimes greatly, and there are distinctions between the different groups of primates.
• Taxonomists identify two suborders in the order Primates, which are the Strepsirrhini, consisting of prosimians, and the Haplorrhini, which includes all species of tarsiers, monkeys, apes, and humans.
• There are two groups of Strepsirrhini, or prosimians: lemurs and a group that includes the lorises and galagos. Strepsirrhines have smaller body sizes than other primates, a smaller brain- to-body-size ratio (still larger than most other mammals), and a keener sense of smell (olfaction) than other primates.
• Most Strepsirrhines are arboreal: living in the trees.

• Many Strepsirrhines are nocturnal: active during the nighttime.

• This means they are active at night, with large eyes and excellent night vision.
• Lemurs live exclusively on the island of Madagascar, off the southeastern coast of Africa, where they arrived approximately 54 million years ago. The absence of other primates on Madagascar until the arrival of humans allowed them to spread out, adapting to different food sources and habitat types.
• Galagos are a group of small, nocturnal species found across forests in central Africa. They have specialized arms and legs that provide great leaping ability.
• Lorises consist of the Asian lorises and the African pottos. They are mostly nocturnal and fully arboreal, eating insects and other small animals. The lorises do not leap in the trees but move slowly through them, using all four limbs to grasp branches.
• There are two infraorders (groupings below the level of the order) of Haplorrhini: Tarsiiformes and Simiiformes.
• Tarsiiformes include the tarsiers (family Tarsiidae). Simiiformes include three superfamilies:
• Ceboidea, or monkeys of the Americas; Cercopithecoidea, or Asian and African monkeys; and Hominoidea, or apes and humans.
• Two specialized terms are used to refer to the Simiiformes:
• Anthropoid: a Primate superfamily that includes monkeys, apes, and humans.
• Hominoid: the Primate superfamily Hominoidea that includes all of the apes and the humans.
• Note that only Homo sapiens, our own species, is included in hominine: the division (called a tribe) in the superfamily Hominoidea that includes humans and our recent ancestors.

• Haplorrhines have larger bodies and larger brain-to-body-size ratios, lack a wet nose, and have more brain devoted to vision than olfaction. They show greater diversity in lifeways (tree-living, ground living, and a mix of both), so their skeletons are more varied.
• Tarsiers are found in Southeast Asia. They are small-bodied and nocturnal, have elongated tarsal bones allowing for extreme leaping abilities, and spend their lives in small groups, typically two adults with their young.
• Ceboidea, or New World Monkeys, range from Southern Mexico to Southern Argentina. The majority are arboreal and relatively smaller than the anthropoids of Africa and Asia. They differ in other ways, including dental and other anatomical characteristics, and possess an important skeletal adaptation for life in the trees is the prehensile tail, which grasps and clings to branches and foliage. A fleshy pad at the tip of the tails even has its own “fingerprint.”
• Cercopithecoidea, or Old World monkeys, are found in Asia and Africa. There are two subfamilies, the cercopithecinae and the colobinae. Baboons and macaques are cercopithecinae, and are both active in the daytime in two contexts—arboreal and terrestrial: living on the ground.
• African apes (gorillas and chimpanzees), Asian apes (orangutans and gibbons) and humans are all members of Hominodiea. All except gibbons have large bodies and brains. Apes and humans don’t have tails but have various adaptations in the upper body permitting full rotation of the arm and greater hand movement, allowing them to hang and swing among branches. The initial adaptation for swinging from limb to limb (so-called brachiation) eventually led to bipedal walking, unique to the human lineage.
• Primate studies within anthropology began in the 1950s and drew from the idea that human social behavior (as well as many physical characteristics) evolved from primates. It became a field science in the 1960s. Biological anthropologists have been key players in the creation of primatology as an interdisciplinary field, identifying and describing new species, standardizing methods, and performing long-term studies.
• Anthropologically-specific approaches to primates are often approached through study of living primates as a window into the evolution of social behaviors among humans.
• Anthropologists also bring holistic, comparative, and cross-cultural perspectives to the study of primates, rather than viewing primates as programmed by their biology and evolution. Anthropologists are attuned to the flexibility and plasticity of primate behaviors, which are rooted in cognitive and social complexity.
• Anthropological studies of primates recognize that humans and primates share historically deep and complicated relationships with each other, competing for food and space, and shaping each other’s ecologies, health, and evolutionary histories, as the Ebola case demonstrates.
• An emerging approach to primate studies called ethnoprimatology: the study of the interface between human and ape communities.
• Ethnoprimatology recognizes that many cultures around the world have strong and variable connections to primates. Many are expressed in religious beliefs, local attitudes, and informal, everyday interactions and are not merely competitive but also based on building intricate relationships.
• From an ethnoprimatological perspective, studying the co-existence of primate species with humans is thus as much about studying primate behaviors as it is understanding how humans think about them and under what conditions the different species come into contact with each other.

What Are The Basic Patterns Of Primate Behavioral Diversity, And Under What Conditions Did They Develop?

• In creating a comparative baseline for understanding humans, anthropologists look for three kinds of behavioral patterns in primates: primate-wide trends, hominoid-wide trends, and unique human characteristics.
• Primates share a number of common behavioral patterns, all of which are connected to the requirements of living in groups and negotiating social relationships and may have some genetic basis.
• The mother-infant bond means that there is a long period of infant dependency where the infant relies totally on others for its nutrition, movement, regulation of body temperature, and protection from predators. Mothers and other relatives have a clear evolutionary interest in ensuring the offspring will reach maturity. This relationship has the infant in frequent physical and vocal contact, and exposed to the mother’s behavior and relationships which helps infants learn crucial information about other group members, foods, and appropriate behaviors. Caregiving is a learned behavior, gained through individual experience and observations of how other group members handle infants.
• The ability to get along with others is critical for primates, given that they live in social groups. Individuals in frequent contact with each other develop an affiliation: a relationship between individuals who are frequently in close association based on tolerance, even friendliness.
• In contrast, an agonistic relationship exists where individuals are in conflict with each other. Primates create affiliations and avoid agonism through grooming: touching another individual to remove dirt, insects, and debris, usually as a way for individuals to bond.
• Unequal access to resources is typical in primate groups and leads to what we call dominance hierarchy: the ranking of access to desired resources by different individuals relative to one another.
• Often the hierarchy is obvious, and an “alpha animal” has priority over other members of the group. In these situations, individuals have priority over others except those who outrank them. Dominance is a social role, not an inborn trait, which an individual occupies for a period in their life.
• While in most societies, males are often dominant over females, there are circumstances in which, due to environmental circumstances, females are dominant, males and females are co-dominant, or individuals do not compete openly with one another and so dominance is not clear. The male-female dominance is, in many primate societies, reinforced by sexual dimorphism: a difference between the sexes of a species in body size or shape.
• The life cycle of a primate lives involves several main stages, including growth and development, reproductive maturity, and old age and death. At some point, usually as they begin to enter reproductive maturity, selected members leave the group, referred to as dispersal: a pattern of one sex leaving the group they were born into about the time of reproductive maturity.
• It is rare for primates to spend much time alone, and they maintain social relationships through acts of cooperation. Dominance relationships tend to maintain social order, and serious fighting or conflicts are rare, and damage to alliances must be repaired. Reconciliation is achieved by behaviors such as sharing, embracing, or other forms of post-conflict physical contact.
• These basic common patterns evolved over millions of years and are shared by all primates. If primates have a set of common behavioral patterns, we may wonder how and why differences in behavior emerge out of those basic common patterns.
• Primate behaviors involve complex interactions between morphology, learning and experience, environmental circumstances, and chance occurrences. Anthropologists can begin to explore answers to these questions by studying how ecological conditions challenge organisms, and how those organisms deal with environmental pressures through behavioral evolution. This is the field of behavioral ecology: the study of behavior from ecological and evolutionary perspectives.
• Socioecological pressures act individually on an organism but, more often than not, particularities in that organism’s environment intersect in unique ways to present individuals with a range of challenges. Differences in behavior emerge out of the ways organisms respond to those particularities. Socioecological pressures on primates come in four primary forms:
• Nutrition, or the necessity of sufficient food and water.
• Locomotion, or the necessity to move around in an environment.
• Predation, or the necessity to avoid predators.
• Competition, or the necessity to gain access to resources in a context in which members of the same species (“intraspecific competition”), or other species (“interspecific competition”), compete for the same resources.
• Within behavioral ecology, understanding an organism’s response to socioecological pressures also involves the concept of costs and benefits: an analytical approach that considers the caloric cost of obtaining food and the calories obtained.
• This basic economic model (cash in and out) measures energy expenditure and can help determine whether a certain behavior gives back to the organism what it expended. Behavioral ecologists assume it is in the interest of organisms to maximize their net energy gains and minimize their costs to support their reproductive success, something referred to as a strategy: a set of behaviors that has become prominent in a population as a result of natural selection.
• One of behavioral ecology’s goals is predicting how animals should behave if the patterns of behavior benefit the primates. An important aspect of behavioral ecology is kin selection: the behavioral favoring of your close genetic relatives.
• Kin selection was proposed to explain altruism: seemingly “selfless” acts that have a net loss of energy to the actor but a net gain in energy to the receiver.
• In evolutionary terms maximizing the fitness of other individuals makes no sense, because it reduces the energy available to an individual. Kin selection offers a simple way of predicting when an individual organism behaves in a way that looks altruistic: when an individual receiving a benefit from another individual is related, then their shared genotype benefits (depending on the degree of relatedness).
• A significant limitation of cost-benefit analyses is their inability to deal with great complexity. It is extremely difficult to identify direct causal links between genes and behavior. Ecological conditions create a range of selection pressures for which certain behavioral responses might be appropriate, but some behaviors will be more successful than others. Those possible behaviors exist along a spectrum. The spectrum establishes the potential for a trait or behavior. The actual expression of the trait or behavior is its performance. Potential and performance are complexly intertwined.

How Do Behavior Patterns Among Monkeys And Apes Compare With Humans?

• Humans are not monkeys and did not evolve from them. The same is true of apes like chimpanzees, gorillas, or orangutans. Despite certain behavioral commonalities across all primates, monkey behavior patterns and morphology differ in key respects from hominoid (ape and human) patterns.
• Understanding how these patterns vary among actual primates requires use of a comparative approach. We now examine a kind of monkey called a macaque and a kind of ape called a chimpanzee, and reflect on how the behavior patterns of each compare to our own behavior as humans.
• Macaque monkeys (members of the genus Macaca) are among the most widely dispersed of all primates. Among the nonhuman primates, macaques have adapted to the widest and most diverse environmental conditions.
• The feeding pattern of macaques is a generalist one. They spend most of their time in the trees, but most species also move along the ground.
• Most macaques live in groups with adult males and adult females. Males leave their birth groups and join other groups, while females stay throughout their lives with their female relatives. This particular arrangement is known as a matrifocal unit: a cluster of individuals generally made up of related females.
• Dominance relations among macaques are closely aligned with sex. Between matrifocal units, more dominant units tend to push others from the best sources of food. Macaques have a unique ranking system among primates, in which a mother’s rank is passed to her youngest daughter, which allows younger females who are the daughter of a high-ranking female to take resources from older, lower-ranked, females.
• Male macaques also have relationships involving dominance of one individual over another which change frequently within any particular group or cluster. Males must form associations with other individuals to help them resolve and negotiate disputes. Because males move between groups, their rank is always fragile compared with that of females, which exposes them to risk.
• Sexual behavior in macaques varies a great deal. Most females mate with more than one adult male, and sometimes mate with all of the males in a group. Many macaques are seasonal breeders, which means they are receptive only at certain times of the year.
• Jane Goodall’s research focused attention on behavior patterns among chimpanzees and their similarity to human patterns of behavior. Since that work, researchers have asked comparative questions about primates and the evolution of human behavior. The gorilla and the chimpanzee are our closest evolutionarily relative. Chimpanzees share many primate-wide behavioral traits as well as shared-derived (hominoid and homininee) morphological and behavioral traits with humans.
• Both Pan troglodytes (chimpanzees) and Pan paniscus (bonobos) are found across Central Africa. They are primarily fruit eaters, and their lives and behaviors are oriented toward the seasons and the times when particular fruits are available.
• Both species live in communities consisting of many adult males and females. Most individuals spend the majority of their time in subgroups characterized by a mix of ages and sexes.
• Among common chimpanzees, males are more often dominant over females, but both males and females typically establish dominance relationships within their sex, which affects access to preferred foods as well as sexual partners.
• Male chimpanzees generally attain high rank from the alliances they form with other males. Male competition does sometimes cause serious injuries and even occasionally death.
• Among female chimpanzees, high rank often results in improved access to food sources and in some areas this is associated with higher rates of infant survivorship.
• Bonobo behavioral patterns involving dominance differ from those of common chimpanzees. Female bonobos are generally dominant over males. Among bonobos it is females who typically display their dominance by dragging objects like tree branches to get the attention of others. Dominance interactions rarely lead to serious fighting. Instead, conflicts are resolved via genital-genital rubbing and other kinds of non-reproductive sexual behavior.
• Among male bonobos, dominance hierarchies do exist, but most commonly a male’s rank is linked to the rank of his mother.
• As regards sexual behavior, females in both species show observable signs of fertility. Females can be observed soliciting copulation, often with several males. Female choice in sexual partners plays an important role in both species, yet there is little evidence that bonobo males can effectively restrict female mating choices, since the females are usually dominant over males.
• Because it superficially resembles human patterns of fighting, chimpanzee and bonobo incidents of intergroup fighting has received a great deal of attention. Among common chimpanzee populations, researchers have reported incidents of intercommunity conflict that end with some deaths. Groups of males circulating around the community’s geographic perimeters, have been seen in most populations – a kind of border patrol. But the pattern of chimpanzee and bonobos patrolling their perimeters seems quite different from the broader patterns of aggression and violence found in many human communities, and violent incidents seem much less significant among both Pan species than in our own.
• Tool use has long been considered a hallmark of humanity. We now know that many organisms use objects aside from their limbs or mouths to get food. Both chimpanzee species exhibit a wide variety of tool modification and use.
• Comparison of different species is a challenge and must be done systematically.
• Humans and macaques share some general characteristics:
• The existence of mixed groups of males and females, social interactions around kin relations.
• Widespread dispersal based on remarkable adaptability.
• Similarities in our dominance hierarchies, including how we establish and maintain them.
• Both of our species are able to survive in diverse habitats.
• There are also critical differences between humans and macaques:
• Significantly different body morphologies
• How we move around through locomotion.
• The size of our brains.
• The scale and complexity of social organization.
• Significant differences between male and female life patterns, which most human societies don’t have.
• Comparison between both Pan species and humans is a more complicated process.
• We share a commonality in living in community.
• Division into subgroups and the types of relationships between individuals in communities have elements of similarity.
• Male-to-male bonding in the context of aggression is similar, as is the social use of sex.
• Both humans and Pan species hunt for meat and other foods, tasks allocated among certain group members.
• Sexual aggression, mate guarding, and aggression between communities might superficially seem like rape, marriage laws, and war in humans.
• There are significant questions about the nature of human and chimpanzee social patterns, with two quite different possibilities:
• the patterns are analogous: similar in appearance or function, not the same due to shared ancestry.
• the patterns are homologous: similar due to shared ancestry.
• the patterns are not even comparable because they are totally distinct behaviors.
• The two chimpanzee species exhibit behavioral diversity, both within their species as well as between them, which makes comparisons with humans difficult. For more than 6 million years, humans and chimpanzees have been on different evolutionary paths, and the chimpanzee species and subspecies are more evolutionarily similar to one another than they any are to humans. More importantly, humans have dispersed more widely, adapting to many more environments on the basis of adaptations that are not genetically rooted, but culturally-mediated.

What Does Studying Monkeys And Apes Really Illustrate About Human Distinctiveness?

• Claims about how humans and primates overlap in morphological, genetic, and especially behavioral terms have proliferated and become more refined. How do we understand human distinctiveness?
• Different natural and social scientific disciplines studying primates answer this question differently. For most anthropologists, it is not just a matter of simply listing the behavioral characteristics of primates and humans and checking off those that appear similar and crossing off others that do not. It is necessary to take a holistic and comparative approach that brings biological and anthropological data and theories into synergistic communication with each other.
• See “Classic Contributions: Sherwood Washburn and the New (Integrative) Physical Anthropology”
• Human distinctiveness is deeply informed by the integration of biology and anthropology, which links our distinctiveness to the characteristics of the social behaviors and organization we have developed. Most of human evolutionary history has involved humans living in small groups of mostly genetically-related individuals, cooperating together in foraging, defense, and raising the young. About 2 million years ago, these early humans began moving out of Africa and encountered new environmental challenges. To meet those challenges, those humans relied on tools and basic forms of social cooperation and alliances.
• Anatomically-modern Homo sapiens usher in radically different social behavior. The size of human social groups grows and these groups tend to become more sedentary. They seem to develop divisions of labor within the group, creating new social roles. Between 20,000 to 40,000 years ago, permanent settlements appear. Agriculture enables population growth and environments begin to change, and cultural differences between groups increases. When compared with other primates, humans have certain unique qualities. Although certain elements resemble what we see in primates, no single primate exhibits them all. No primate species mediates these relationships and behaviors so thoroughly through culture.
• Recently, the idea that nonhuman primates have “culture” has become more popular. Some non-human species of primates do exhibit patterns of behavioral variation across groups, based on specific behaviors that are shared, learned, and maintained on a group-by-group basis, which suggests that these behavioral patterns are not reducible either to genetic or to ecological factors, but does not answer the question of whether they might be a simple form of culture.
• Use of the term “culture” to describe these behavior patterns is controversial among social and humanistic scholars as well as scientists studying other non-primate animals. We simply do not know when enough behaviors are “cultural” to declare that the species as whole exhibits culture.
• There is a tendency to reduce culture to socially-transmitted learning, something that is not unique to primates; Norway rats and Japanese quail, for example, also exhibit social learning. Primatologists counter that in those species social learning relates to only single behaviors, while in chimpanzees and bonobos, the social transmission of behaviors is more complex and extensive.
• From an anthropological perspective, reducing culture to the social transmission of behaviors and variation across groups is a vast oversimplification of how much language and symbolic abstraction lie at the heart of what culture is and how it works.
• Symbolization, personification, metaphorization, and abstraction are all mediated through culture, providing humans with a capacity not simply to interact with actual worlds but to imagine and construct them, and hold two competing thoughts simultaneously. Studying behavior alone is not sufficient to understand culture; we also need to understand and interpret how people think and how those thoughts inform and guide their actions.
• This does not deny that nonhuman primates like chimpanzees exhibit remarkable behavioral flexibility and plasticity. For anthropologists, culture and language enable humans to communicate content not accessible to other organisms and, combined with our use of symbolic representation, allows us to acquire, manipulate, and disseminate knowledge more extensively than any primate species.
• Evolutionary changes that define us as human arose over time and continue to arise. All three primates have distinct bodies and minds that are the result of separate evolutionary trajectories.

Conclusion

• Understanding what we have in common with the other living primate species provides an important comparative baseline for understanding ourselves and what we have inherited biologically as a species. Using the information generated by studying nonhuman primates, anthropology is in a better position to reconstruct aspects of human evolution, to better understand what is general to primates, what is restricted to a few kinds of primates and humans, and what is uniquely human.
• Anthropologists are also interested in the interface between primates and humans. As as the movement of Ebola viruses between and among West African human and ape populations demonstrates, understanding those interfaces has important practical and public health dimensions.
• Humans are similar to other primates in a number of ways, yet specific aspects of our evolutionary history have resulted in a distinct trajectory of biocultural adaptation.
• No other primate is a perfect model for human evolution because even our closest relatives, the chimpanzees, have experienced millions of years of separate evolution.