Chapter 4: the primates

4. Understand what prosimians are, where they live, and how they are related to other primates.

5. Know the differences between New World and Old World monkeys.

6. Be able to identify and distinguish between the apes.

7. Be able to discuss both similarities and differences between humans and the other primates.

8. Be able to identify and distinguish between the Early Cenozoic primates and the Oligocene anthropoids.

9. Be able to identify and distinguish between the Miocene hominoid species.
10. Understand the threats that are endangering primates around the world.

Chapter Outline

I. Primatology

A. Primatology is the study of nonhuman primates—fossil and living apes, monkeys, and prosimians—including their behavior and social life.

B. Primatology helps anthropologists make inferences about the early social organization of hominids (members of the zoological family that includes fossil and living humans).

A. Definitions of key terms

1. Taxonomy: the assignment of organisms to categories (taxa; singular taxon) according to their relationship and resemblance.

2. Hominoidea (hominoids): the superfamily containing humans and apes.

3. Phylogeny: genetic relatedness based on common ancestry.

B. Zoological Taxonomy

1. Organisms are placed in taxa, which are arranged hierarchically according to degree of genetic relatedness.

2. Homologies, or similarities inherited from a common ancestor, are used to assign organisms to the same taxon.

3. Humans belong to the class Mammalia (along with other mammals) and the order Primates (along with other apes, monkeys, and prosimians).
III. Homologies and Analogies

A. Taxonomic classification of organisms should be based solely on homologies.

B. Analogies

1. Analogies are similarities between species that are the result of similar adaptation to similar selective forces, rather than common ancestry.

2. Convergent evolution is the process by which analogies are produced.

C. Hominidae is the zoological family that includes hominids—fossil and living humans as well as (according to many scientists) gorillas and chimps.

A. Because the earliest primates were tree dwellers, modern primates share homologies reflecting their common arboreal heritage.

B. There are several trends in primate evolution that are best exemplified by the anthropoids (monkeys, apes, and humans—members of the suborder Anthropoidea).

1. Five-digited, flexible hands and feet that are well suited for grasping (including opposable thumbs in humans and many other primates).

2. Anatomical changes (stereoscopic and color vision, expansion of the portion of the brain devoted to vision) reflecting a shift from smell to sight as the primates’ most important means of obtaining information.

3. Increased reliance on the hands as the primary touch organs, rather than the nose or whiskers.

4. An increase in the proportion of brain tissue concerned with memory, thought, and association.

5. Increased parental investment in single offspring, resulting in more opportunities for learning.

6. Sociality, or living in groups, which is selected for because of the need for longer and more attentive care of offspring.
V. Prosimians

A. Prosimians (lemurs, tarsiers, and lorises) and anthropoids (monkeys, apes, and humans) constitute the two suborders of primates.

B. The earliest primates, represented in the fossil record, were prosimian-like animals.

C. Because they are nocturnal (active at night), some prosimians in Africa and Asia have been able to avoid competition with anthropoids, which first appeared some 50 million years ago and are diurnal (active during the day).

D. Lemurs in Madagascar did not have to compete with anthropoids until the island was colonized by humans some 1,500 years ago.
VI. Primate Trends: Anthropoid Traits

A. Depth perception and color vision may have evolved together because they proved adaptive in arboreal environments.

B. Along with changes in vision, increased sensitivity of the fingers and increased manual dexterity (e.g., an opposable thumb) would have been important for feeding, grooming, examining and manipulating objects, and tool making.

C. Increased brain size (relative to body size), as well as expansion of the brain’s outer layer (responsible for memory, association, and integration), enhanced anthropoids’ ability to learn from experience and from other individuals.

A. Platyrrhines and Catarrhines

1. There are two anthropoid infraorders: platyrrhines (flat-nosed, New World monkeys) and catarrhines (sharp-nosed, Old World monkeys, apes, and humans).

2. Whereas all monkeys have arms and legs that move parallel to one another, apes and humans exhibit orthograde posture (straight and upright stance).

3. Monkeys have arms and legs of about the same length, and most have tails, whereas apes and humans lack tails and have arms and legs of different lengths.

B. New World Monkeys

1. New World monkeys live in the forests of Central and South America.

2. Whereas many New World monkeys have prehensile (grasping) tails, Old World monkeys have rough patches of skin on their buttocks, adapted to sitting on hard rocky ground and rough branches.

C. Old World Monkeys

1. Old World monkeys include both terrestrial and arboreal species.

2. Among Old World monkeys, arboreal species tend to be smaller than terrestrial species, and terrestrial species exhibit greater sexual dimorphism (males are larger and fiercer than females).

3. Among terrestrial monkeys (baboons and macaques), the core group consists of females, while among apes (chimpanzees and gorillas) it is made up of males.

A. Old World Monkeys comprise the superfamily Cercopithecoidea, while humans and apes are in the superfamily Hominoidea (hominoids).

B. The great apes include orangutans, gorillas, and chimpanzees (and perhaps humans), while the lesser (smaller) apes include gibbons and siamangs.

C. Gibbons

1. Gibbons, the smallest of the apes, live in the forests of Southeast Asia, particularly Malaysia.

2. Gibbons’ principal mode of locomotion is brachiation (hand-over-hand movement through the trees).

3. Gibbons and siamangs, their slightly larger relatives, generally live in primary groups composed of a permanently bonded male and female pair and their preadolescent offspring.

D. Orangutans

1. Orangutans are highly endangered and confined to two Indonesian islands.

2. Orangutans are intermediate in size between chimps and gorillas, markedly sexually dimorphic, and generally solitary.

3. Orangutans move between arboreal and terrestrial habitats.

E. Gorillas

1. There are three subspecies of gorillas (western lowland, eastern lowland, and mountain) found in different regions of Africa.

2. Gorillas are large (up to 400 pounds), markedly sexually dimorphic, and primarily terrestrial.

3. Gorillas live in relatively stable social groups, each typically led by a mature silver-back male.

F. Chimpanzees

1. There are two kinds of chimpanzee: the common chimpanzee (Pan troglodytes) and the bonobo or “pygmy” chimpanzee (Pan paniscus).

2. The common chimp is found in western central, western, and eastern Africa.

3. Chimps are lighter and more arboreal than gorillas, and they exhibit sexual dimorphism similar to that among humans.

4. Chimpanzee behavior and social organization are relatively well understood because of longitudinal studies conducted by Jane Goodall and other primatologists.

G. Bonobos

1. Bonobos live in the humid forests of the Democratic Republic of Congo.

2. Despite their common name (the pygmy chimpanzee), the size range of bonobos overlaps with that of common chimpanzees.

3. Bonobo communities are female-centered, peace-loving, and egalitarian.

4. The frequency with which bonobos have sex, and use it to avoid conflict, makes them exceptional among the primates.
IX. Human-Primate Similarities

A. Learning

1. The behavior and social life of monkeys, apes, and humans is not rigidly genetically programmed.

2. The ability of monkeys, apes, and humans to learn throughout their lives, and to modify their behavior and social patterns, confers a tremendous adaptive advantage.

B. Tools

1. Although humans use tools much more than other animals do, tool use is not unique to humans.

2. Wild chimpanzees have been observed constructing and using tools (“termiting” sticks).

C. Predation and Hunting

1. The diets of other terrestrial primates (e.g., baboons, chimpanzees) are not exclusively vegetarian.

2. Hunting, both opportunistic and planned, has been observed among wild chimpanzees, who may even form large hunting parties.

A. Sharing, Cooperation, and Division of Labor

1. Although sharing and cooperation occur among nonhuman primates, humans are the most cooperative primate species.

2. In adapting to an omnivorous diet over millions of years, hominids came to rely heavily on hunting, food and information sharing, and cooperative behavior.

B. Mating and Kinship

1. In contrast to other primates, humans mate throughout the year, and human pair bonds tend to be more exclusive and more durable.

2. Human marriage and kinship systems create ties of affection and mutual support between members of different local groups—relationships that are generally absent among nonhuman primates.
XI. Primate Evolution
XII. Chronology

A. The history of vertebrate life on earth is divided into three eras: the Paleozoic, the Mesozoic, and the Cenozoic.

B. Each era is divided into periods, and each period is divided into epochs.

C. Anthropologists are concerned with the Cenozoic era, which includes two periods: the Tertiary and the Quaternary.

1. The Tertiary had five epochs: Paleocene, Eocene, Oligocene, Miocene, and Pliocene.

a. A wide range of small mammals, some possibly ancestral to primates, appeared during the Paleocene (65 to 54 million years ago [m.y.a.]).

b. Prosimian-like fossils abound in strata dating to the Eocene (54 to 36 m.y.a).

c. The first anthropoid fossils date to the Eocene and the early Oligocene (36 to 23 m.y.a.).

d. Hominoids became widespread during the Miocene (23 to 5 m.y.a.).

e. Hominids first appeared during the late Miocene, just before the Pliocene (5 to 2 m.y.a.).

2. The Quaternary period had two epochs: Pleistocene and Holocene.
XIII. Early Primates

A. Arboreal theory

1. According to the arboreal theory, primates became primates by adapting to life in trees.

2. Changes in the visual apparatus were adaptive in the trees, where depth perception facilitated leaping.

3. Grasping hands and feet facilitated arboreal locomotion, as well as feeding.

B. Early Cenozoic Primates

1. The earliest primates probably lived during the first epoch of the Cenozoic, the Paleocene (65-54 m.y.a.).

2. The Eocene (54-38 m.y.a.) was the epoch of the prosimians, with at least 60 different genera in two main families.

3. Anthropoids branched off from the prosimians during the Eocene by becoming more diurnal (active during the day) and by strengthening the trend favoring vision over smell.

a. In contrast to prosimians, anthropoids have eyes that are rotated more forward, a fully enclosed bony eye socket, a dry nose separate from the upper lip, and molar cusps.

b. Many prosimian species became extinct by the end of the Eocene, as a result of competition with the first anthropoids.

C. Oligocene Anthropoids

1. During the Oligocene epoch (38-23 m.y.a.), anthropoids became the most numerous primates.

2. The parapithecid family may be ancestral to New World monkeys.

3. The propliopithecid family may be ancestral to Old World monkeys, apes, and humans.
XIV. Miocene Hominoids

A. The earliest hominoid fossils date to the Miocene epoch (23-5 m.y.a.).

B. Proconsul

1. The Proconsul group, found in Africa, represents the most abundant and successful anthropoids of the early Miocene.

2. Proconsul species had teeth with similarities to those of modern apes, but their skeleton below the neck was more monkey-like.

3. Proconsul probably contained the last common ancestor shared by Old World monkeys and the apes.

C. Later Miocene Apes

1. More than 20 species of proto-apes dating to the middle Miocene (16-10 m.y.a.) have been discovered.

2. Gigantopithecus

a. Gigantopithecus was probably the largest primate that ever lived.

b. There were at least two species of Gigantopithecus—one that coexisted with members of our own genus, Homo erectus, some 400,000 years ago in China and Vietnam, and another that lived much earlier (5 m.y.a.) in northern India.

D. Pierolapithecus catalaunicus

1. Pierolapithecus catalaunicus, which lived around 13 million years ago (during the middle Miocene), may be the last common ancestor of humans, chimpanzees, gorillas, and orangutans.

2. Like modern chimps and gorillas, Pierolapithecus was well adapted for tree climbing and knuckle-walking.

3. At the same time, certain anatomical features distinguished Pierolapithecus from the lesser apes and monkeys.

E. “Toumai”

1. Toumai is the local name (Sahelanthropus tchadensis is the scientific name) for a 6 to 7 million-year-old primate skull found in northern Chad.

2. This fossil, which blends human and apelike characteristics, may be the remains of the oldest human ancestor yet found.

F. Orrorin tugenensis

1. Fossils from Orrorin tugenensis, a primate (possibly a hominid) that lived after Toumai, were found in Kenya’s Baringo district.

2. The anatomical features of Orrorin suggest that it was able to climb trees easily as well as walk on two legs (bipedalism).
XV. Box: Endangered Primates

A. Humans are the only primates that are not endangered (or soon to be endangered).

B. Deforestation, hunting, and the capture of primates for use in labs or as pets are all contributing to the demise of wild primate populations.

Lecture Topics

1. Explain the difference between homologies and analogies, using animals familiar to undergraduates as examples. This discussion can segue into an explanation of the importance of homologies in taxonomic classification.

Primates

1997 53 minutes

Narrated by Armand Assante, this film explores the life of primates in their natural habitats. It discusses the social order, family life, diet, and mating habits of different primate species. A Discovery Channel Production.

Jane Goodall: A Life in the Wild

1990 31 minutes

This film presents the life and work of Dr. Jane Goodall. Interviews with Dr. Goodall reveal why she became a primatologist and how she arrived at some of her more important findings. From Films for the Humanities and Sciences.

Washoe: Apes and Sign Language

1994 53 minutes

This film, made by the researchers who worked with Washoe, shows how this chimpanzee acquired and used sign language. From Films for the Humanities and Sciences.

The Ape: So Human!

1998 41 minutes

This film presents experiments by Allen and Beatrix Gardner, Sue Savage-Rumbaugh, and other primatologists relating to chimpanzee behavior. Particular attention is paid to cognition, self-awareness, memory retention, language use, social behavior, and mating practices. From Films for the Humanities and Sciences.

Ancient Mysteries: Bigfoot

1994 50 minutes

Narrated by Leonard Nimoy, this film traces reports of Bigfoot sightings over thousands of years and discusses the current state of Bigfoot research. Presented by A&E Home Video.

Sasquatch Odyssey: The Hunt for Bigfoot

1999 60 minutes

This film presents the history of the search for Bigfoot, focusing primarily on four well-known Sasquatch researchers: Peter Byrne, John Green, Rene Dahinden, and Grover Krantz. Presented by Big Hairy Deal Films and Gryphon Productions Ltd., West Vancouver, BC, Canada.

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