Download CHAPTER 4: THE PRIMATES

CHAPTER 4: THE PRIMATES
CHAPTER OVERVIEW
This chapter introduces students to the study of living, non-human primates. It discusses the basic
classification of primates and all of the classes of living primates. The chapter pays special attention to the
key trends in primate evolution, as they are best exemplified in anthropoids. It also examines the
similarities and differences between non-human primates and humans, as well as the earliest primate
species that lived during the Eocene, Oligocene, and Miocene epochs.
CHAPTER OBJECTIVES
1.
Be able to discuss how the human relationship to other primates is represented in zoological
taxonomy, as well as the role of analogies and homologies in determining this relationship.
2.
Consider the scope and subject matter of primatology and its specific relationship to the discipline
of anthropology.
3.
Identify the six primary trends in primate evolution, best exemplified in anthropoids.
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 among the apes.
7.
Be able to discuss both the similarities and differences between humans and non-human 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 facing endangered 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).
II. Our Place Among Primates
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.
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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. The Place of Humans in Zoological Taxonomy
1. Hominidae is the name of the zoological family that includes hominids, fossil and
living humans.
2. Many scientists now also place chimps and gorillas in the hominid family.
3. To specify the group that leads to humans but not to chimps and gorillas, the tribe
hominini refers to all the human species that ever have existed (including the extinct
ones) and excludes chimps and gorillas.
IV. What Makes a Primate?
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.
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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.
VII. Monkeys
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.
VIII. Apes
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 in
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
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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 silverback 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. Similarities Between Humans and Other Primates
A. Learning
1. The behavior and social life of monkeys, apes, and humans are not rigidly
programmed by the genes.
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 (e.g., “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.
X. Differences Between Humans and Other Primates
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, hominins 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.
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XI. Primate Evolution: 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. Hominins 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.
XII. 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, and a dry nose separate from the
upper lip.
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.
XIII. 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.
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C.
D.
E.
F.
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.
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.
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 (e.g., its rib cage, lower spine, and
wrist) distinguished Pierolapithecus from the lesser apes and monkeys.
“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.
Orrorin tugenensis
1. Fossils from Orrorin tugenensis, a primate (possibly a hominin) 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).
XIV. Anthropology Today: 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.
An illustration of homologies and analogies by using the various animals commonly familiar to
undergraduates is most effective for demonstrating the difference between the two concepts. Such
discussion also serves as the basis for explaining the importance of homologies in classification.
2.
The adaptive roots of sexual dimorphism (competition among males for sexual access to females,
in the case of most primates), both in external physical pressures and in social relations, should be
explained carefully. Discuss how such adaptive pressures might or might not apply to humans.
3.
Categorize and present the variety of social groupings characteristic of different primate species in
a simple, tabular form that students can recall easily. Explain the adaptive basis for the various
social forms—e.g., mated couples, single-male groups, and groups in which social organization is
based on relationships among female kin (female-bonded groups) or among males (male-bonded
groups).
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4.
A number of studies investigating the nature of sexual relations among nonhuman primates have
attempted to draw conclusions about, for example, the origins of monogamy and marriage, sexual
violence, and the origins of the sexual division of labor. Such issues make interesting topics for
discussion. They may also be used to illustrate the possibilities—and the limitations—of crossspecies comparison and generalization.
5.
Discuss the patterns of hominoid evolution during the Miocene.
SUGGESTED FILMS
Primates
1997 53 minutes
There are 234 primate species, and it seems that the more that is learned about them, the more humans
come to understand themselves. 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 Jane Goodall. Through interviews with Goodall, we learn why she
became a primatologist and how she came upon some of her more important findings. From Films for the
Humanities and Sciences.
Washoe: Apes and Sign Language
1994 53 minutes
This film was made by the researchers who worked with Washoe and shows how Washoe acquired and
used sign language. From Films for the Humanities and Sciences.
The Ape: So Human!
1998 41 minutes
This film presents the experiments by Allen and Beatrix Gardner, Sue Savage-Rumbaugh, and other
primatologists related 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.
Life in the Trees
1986 26 minutes
In this film, David Attenborough explores the evolution of primates in a wide range of geographic areas
and explains the importance of binocular vision and grasping hands in successful adaptation to life in the
trees. Part of the series Life on Earth. From Penn Communications.
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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