ANTH 2010 Chapter 7 Notes

Jane Goodall’s Story
Since childhood, Goodall had dreamed of living in Africa, and in 1957, she traveled with a friend to Kenya. Within 2 months, she had met the famous fossil hunter Louis Leakey, who eventually employed her at the museum in Nairobi. Leakey was interested in human origins and had long thought that studying chimpanzees in the wild would be a window onto the behavior and social organization of early humans. He decided she was the right person to pursue this line of inquiry. She enthusiastically agreed to live among and study chimpanzees in Gombe, in western Tanzania. No one had ever observed chimpanzees in the wild for an extended period or in the kind of detail needed to record behavior and draw conclusions. Moreover, living in the jungle was no easy undertaking. A few months after reaching her field site in 1960, Goodall was able to habituate the chimpanzees to her presence, observe them for hours on end, and record their behaviors in unprecedented detail. Her findings bowled over the anthropological world. Goodall also discovered behaviors that other scientists found quite hard to believe, mainly because the behaviors did not fit expectations about the species. Goodall performed pioneering research that underscored the importance of the study of primate to understanding ourselves. Among her many accomplishments, Goodall documented key elements of primate societies and of primate social behavior in its broadest terms.
Goodall’s Discoveries
First, Goodall documented in words and on film how chimps made stick probes to harvest termites from termite nests, and how they crumpled up leaves to make a kind of sponge, with which they soaked up rainwater from the crooks of trees and then squeezed the water into their mouths. That chimps used tools was an exciting discovery because it narrowed the perceived behavioral chasm between humans and apes.
Second, Goodall discovered that chimpanzees regularly hunted other primates and animals.
Diversity of Primate Societies
1) Behavioral Diversity
2) Organizational Complexity
3) Social Relationships
Diversity of Primate Societies: Behavioral Diversity
First, primates express themselves socially through a range of behaviors. Far more so than any other animal, primates use these social signals to express different kinds of relationships, many of them complex and reciprocal. These signals can serve as a kind of “currency” for items or activities they are interested in.
Diversity of Primate Societies: Organizational Complexity
Second, many primate societies are complexly organized. Within any primate group, individuals representing different kinships, ranks, ages, and sexes often form alliances.
Diversity of Primate Societies: Social Relationships
•Third, primates form various social relationships for the long term. Primates form relationships for immediate payoff, but they also establish and maintain long-term alliances that at first glance do not appear to be beneficial, especially with regard to reproductive success.
Primate Sexual Behavior
Males and females have very different reproductive roles and very different life histories in adulthood. Males provide the sperm to produce offspring. Females provide the ova to conceive the young, grow the young within them, give birth, and nurse the young. Overall, females expend far more energy in the creation of and caring for offspring than males do. As a general rule for many animals, including primates, those members of the sex that expends less energy in this way compete more aggressively among themselves for sexual access to members of the sex that expends more energy.
Primate Sexual Behavior: Sexual Dimorphism
When male primates compete for females, whether they are competing singly or in groups, the males’ bodies adapt. Sexual dimorphism in body size and in canine size is considerably higher in such societies than in societies where males do not compete. This difference reflects the fact that to compete for females successfully, males must be big and aggressive. In these societies, males are generally unrelated. In societies where males are related, live in the group in which they were born (the natal group), and compete with related males, sexual dimorphism tends to be lower than in groups where males disperse and compete with nonrelated males.
Primate Life Spans
Finally, although all the life periods of primates are longer than those of other animals, humans have the longest life span.
Primate Residence Patterns
Individual primate species combine different patterns, and their social groups are strongly influenced by factors such as food availability, environment, and competition. Primatologists have identified six main types of primate residence patterns:
1) One-male, Multi-female
2) One-female, Multi-male
3) Multi-male, Multi-female
4) All-male
5) One-male, One-female
6) Solitary
Primate Residence Patterns: One-male, Multi-female
One-male, multifemale. This haremlike organization consists of one reproductive-age male, several mature females, and the immature offspring. The society is polygynous, meaning that the one male has more than one partner. Some howler monkeys, some langurs, and some Old World monkeys practice this social system.
Primate Residence Patterns: One-female, Multi-male
One-female, multimale. This group consists of one reproductive-age female, several mature males, and the immature offspring. The society is polyandrous, meaning that the one female mates with nonpolygynous males. The males often cooperate with the females in parenting activities. Only some New World monkeys practice this social system, and only rarely.
Primate Residence Patterns: Multi-male, Multi-female
Multimale, multifemale. This group consists of many adults, male and female, and the offspring. Both sexes mate promiscuously. Competition for mates tends to be relatively low, especially among males. Many Old World monkeys, a few New World monkeys, and chimpanzees fit in this category.
Primate Residence Patterns: All-male
All-male. In some species, such as baboons, males form at least temporary groups, typically before joining or forming groups that include males and females. All-male groups commonly exist together with multimale, multifemale groups.
Primate Residence Patterns: One-male, One-female
One male, one female. This group consists of an adult male, an adult female, and their immature offspring. Mating is typically monogamous, so each partners’ reproductive success is tied to that of the other, and the male invests a relatively large amount of time and energy in the young. Gibbons, siamangs, a couple of ceboids, and several species of prosimians practice this form of society.
Primate Residence Patterns: Solitary
Solitary primates go it alone—rarely are individuals seen with others. Interaction between adult males and adult females occurs only for sexual activity. Only orangutans and a few prosimians are solitary.
Primate Reproductive Strategies: Males
Males’ primary strategy is to physically compete for access to reproductively mature females, resulting in a strong degree of natural selection in males for both large bodies and large canines. This form of natural selection is called sexual selection. Another male strategy is infanticide, the killing of a nursing infant, primarily by a foreign male who has driven the single male out of a one-male-, multifemale group. The new male kills the nursing infant so that its mother stops lactating, resumes ovulation, and becomes sexually receptive to him. As a result, the new male enhances his reproductive fitness, largely at the expense of the previous male.
Primate Reproductive Strategies: Females
Females compete with each other for resources that enable them to care for young. In various New World and Old World monkeys, the competition for resources happens within the context of stable dominance hierarchies. Hierarchical ranks usually pass from mother to daughter, and younger sisters usually rank higher than older sisters. The higher the rank, the greater the ability to acquire important resources. Higher ranked females also tend to have more offspring. In some primates, higher-ranked females have a greater number of offspring because they begin reproducing months before lower-ranked females. In addition, some female primates are relatively more selective in choosing mates than are others, making the selection on the basis of characteristics such as dispositions, physical appearance, and position in social hierarchy. Some adult females’ social behaviors encourage support for and investment in their offspring by other members of the group. And some adult females protect their infants from aggression.
Cooperation in Primates: Chimpanzees
Primates are also highly cooperative social animals. Chimpanzees hunt in groups of cooperating males, often preying on juvenile monkeys. Chimpanzees also share food following a hunt.
Cooperation in Primates: Warning Calls
Other primates issue warning calls to their social group when predators approach.
Cooperation in Primates: Grooming
Many primates groom each other. In nonhuman primates, grooming involves one individual picking through the skin and hair of another individual, removing insects or other foreign objects, sometimes eating these materials. Among this practice’s functions are bonding two members of a social group, calming the primate being groomed, or appeasing that primate if he or she has a higher position in a dominance hierarchy.
Cooperation in Primates: Altruism and Kin Selection
Some cooperative behaviors are altruistic, in that they appear to reduce the reproductive fitness of the individuals performing them but enhance the recipients’ reproductive fitness. Altruism seems not to be directed haphazardly, but rather is directed primarily at relatives. According to the British evolutionary theorist William Hamilton’s hypothesis of kin selection, the evolutionary benefits of an altruistic behavior to the kin group outweigh the costs to the individual acting altruistically.
Who Hypothesized About Primate Kin Selection and Altruism?
Theorist William Hamilton.
Cooperation in Primates: The Big Picture
Cooperation has many advantages, but it ultimately provides most primate taxa with their distinctive behavioral characteristic: primates live in social groups. And the primary reason for these social groups is probably that while many primates are proficient predators, primates are preyed upon by a range of predators. Defense from predators would seem to be an important form of cooperative behavior. However, the evidence of primates’ protecting each other from predators is slim. Many primates are preyed upon by large birds, such as eagles. The results show that predation rates are lower among larger primate groups than among smaller primate groups.
Getting Food: Everybody Needs It, But the Burden is on Mom
Primates acquire their food through a wide variety of foraging practices, which entail looking for food the handling and processing the food for consumption. This burden is especially great on mothers. Not only do mothers need to eat food that will provide the energy for gestation and lactation, but they also need to look for food and then handle and process it for their young to consume. In a few primate species, the father is involved in caring for and providing food for the young, but generally the mother is the sole provider of her offspring’s food.
The Importance of Nutrition
For the female primates, success in caring for young, both before and after their birth, is very much tied to adequate nutrition. Females with good nutrition have young at an earlier age, have healthier young, experiences shorter intervals between births, and live longer than those with suboptimal nutrition.
Three Key Factors to a Female Primate’s Nutritional Success
1) Quality
2) Distribution
3) Availability of Food
Three Key Factors to a Female Primate’s Nutritional Success: Quality
Quality refers to food’s providing energy and protein that are readily digestible.
Three Key Factors to a Female Primate’s Nutritional Success: Distribution
Distribution refers to the locations of food across the landscape. Ideally, the primate would have to expend relatively little energy to acquire food. Many primates focus on patches of food, such as a fruit-bearing tree or a group of such trees, whose fruit provides a ready and concentrated source of nutrients. However, a small patch will support only a relatively small group. All primates are able to adjust the size of the feeding group in relation to the amount of food available in a patch.
Three Key Factors to a Female Primate’s Nutritional Success: Food Availability
Food availability can be highly fluid, depending on season and rainfall. The farther a region is from the equator, the more defined are its seasons and the less available are fruit and leaves, primates’ main food sources.
Three Central Features of Chimpanzee Tool Use: Cognition
First, chimpanzees are extraordinarily intelligent and have the complex cognitive skills necessary for at least some kinds of behavior that require learning and the ability to understand complex symbolization.
Three Central Features of Chimpanzee Tool Use: Finding Food
Second, in natural settings where chimpanzees have not been taught by humans, most of the tools chimpanzees produce are for acquiring and consuming food. Among the rare examples of primate tool use unrelated to food is that of chimpanzees in Gombe throwing stones as part of a dominance conflict between adult males.
Three Central Features of Chimpanzee Tool Use: Localization
Third, tool production and tool use are sometimes highly localized. While chimpanzees do not depend on material culture for survival, they nonetheless use material culture. Chimpanzees use several forms of tools and that not all forms occur in all chimpanzee groups. Perhaps local traditions are passed from generation to generation via social learning.
The Significance of Chimpanzee Tool Use
The complexity here is far less than that of human technology, but these simple behaviors show that chimpanzees are not the only primates that interact with the environment through tools they make.
Vocal Communication is Fundamental Behavior in Primate Societies
All primates, from prosimians to apes, produce vocalizations of some type that serve various functions. Some quiet calls can be heard only by nearby group members, while some loud calls convey information over great distances and through dense vegetation. Research has shown that these vocal systems are rich and complex and largely under the caller’s control. The study of primate vocal communication can give us insights into the selective pressures that may have shaped the evolution of language.
“Translating” Primate Calls
To “translate” primates’ calls, scientists first catalog a population’s vocal repertoire. They then determine the contexts in which the members of that population produce the different vocalizations. Primate voices vary just as human voices do, but individuals in groups produce similar calls in all categories. Determining the context of a given call does not unequivocally prove that call’s function. The use of playback experiments has revolutionized what scientists can say about a call’s meaning, albeit only from the listener’s perspective. In conducting such an experiment, the researchers record naturally occurring calls. They then use hidden speakers to broadcast call sequences to the primate group.
Cheney and Seyfarth’s Experiment
In a classic example, the American primatologists Dorothy Cheney and Robert Seyfarth played the sound of an infant vervet monkey screaming to a group of mothers whose infants had all wandered off. Only the mother of that particular infant looked toward the hidden speaker, a finding that suggests females recognize the voices of their own infants. To Cheney and Seyfarth’s surprise, however, the other females looked at the mother of the screaming infant. This finding gave the researchers insight into what primates “know” about each other.
Types of Calls
In this way, researchers have determined that some quiet calls produced by primates mediate social encounters within a group.
If the approaching dominant produced a “threat-grunt,” a version of the call that indicates aggressive intent, the listener would likely flee rapidly.
The loudest calls in a primate species’ repertoire transmit information over long distances and are typically produced during events such as an encounter with predators, an aggressive contest with another group, and one animal’s separation from its group.
Primates: Counting Vocal or Audible Cues
The voices of individual callers within a group do not completely overlap during a chorus; thus it is possible for listeners in another group to “count” the number of rivals they will face based on vocal cues alone. The loud, repetitive call displays produced by adults males reliably indicated the caller’s physical condition. Although primate vocalizations can indicate a caller’s emotional state, many also seem to convey information about the world around the caller.
The Functional Reference of Calls
Listeners treat all sounds in the forest associated with one type of predator the same. These and other experimental results suggest that primate calls can be functionally referential. That is, these calls convey semanticlike meaning, which makes them similar to human words, at least from the listener’s perspective. Like monkeys, chimpanzees can label events and objects. They and many other priamtes have displayed food-associated vocalizations.
Primate Calls: Learned or Innate?
The perception of and response to certain vocalizations is learned. In addition to differences in grooming, chimpanzees show different kinds of vocalizations unique to specific groups and regions. These differences suggest that some vocal features may be transmitted through social learning.
Primate and Human Vocalizations: Similarities
Primatologists are also learning that vocalizations have clear patterns, some of which bear a striking resemblance to the structural elements of human language. Humans change words structure to change meaning. One of the most important examples is what linguists call affixation, whereby a small unit is added at either the beginning or the end of the word stem. Exciting new work reveals that these primates use a kind of affixation by adding suffixes. These primates’ altering of a stem term through the addition of a suffix is a very important discovery because it provides a strong parallel with human word construction. This parallel suggests what the early hominids’ first form of speech may have been like.
Primates and Human Vocalizations: Differences
Humans routinely invent new vocalizations throughout their lives, but nonhuman primates appear to be basically preprogrammed, producing most of the calls typical of their species shortly after birth. However, primates must still learn to use and to respond to these vocalizations appropriately.
Hand Clasp
The primatologist Bill McGrew and his colleagues, while observing chimpanzees in Mahale National Park, Tanzania, were the first to note an unusual grooming technique, the hand clasp. The two participants face one another. Each one holds a hand up over their heads and claps the other’s hand, forming an A-frame, and each uses his or her free hand to pick parasites and other detritus off the other participant. The nearby chimpanzees of Gombe National Park, Tanzania, do not groom in this manner.
The Remarkable Great Apes
In the larger picture, the great apes—especially chimpanzees—are the nonhuman primates with the highest degree of flexibility and most extensive use of material and nonmaterial culture.
While watching his mother being taught by Sue Savage-Rumbaugh and her colleagues, a captive bonobo named Kanzi spontaneously learned to use lexigrams. Kanzi remains one of the most successful non-human users of such a symbolic communication system. He can understand English at the level of a two-year-old human, and he combines lexigrams in new ways according to a set of rules. The researchers argue that Kanzi’s competence reflects an ancient history for a form of proto-grammar.
Ape Language?
Although great apes lack the physical ability to produce human speech, the findings of several “ape language” research projects indicate that they have some of the rudimentary cognitive abilities necessary to understand human speech.