Evolution And History

Communication and Learning 89

games, such as jostling for position on the top of a hill-

side or following and mimicking a single youngster. One

juvenile, becoming annoyed at repeated harassment by an

infant, picked it up, climbed a tree, and deposited it on a

branch from which it was unable to get down on its own;

eventually, its mother came to retrieve it.

Communication and Learning

Primates, like many animals, vocalize. They have a great

range of calls that are often used together with movements

of the face or body to convey a message. Observers have

not yet established the meaning of all the sounds, but a

good number have been distinguished, such as warning

calls, threat calls, defense calls, and gathering calls. The

behavioral reactions of other animals hearing the call

have also been studied. Among bonobos, chimpanzees,

and gorillas, most vocalizations communicate an emo-

tional state rather than information. Much of the com-

munication of these species takes place by using specific

gestures and postures. Indeed, a number of these, such as

kissing and embracing, are used universally among hu-

mans, as well as apes.

Primatologists have classified numerous chimpan-

zee vocalizations and visual communication signals. Fa-

cial expressions convey emotional states such as distress,

fear, or excitement. Distinct vocalizations or calls have

been associated with a variety of sensations. For example,

chimps will smack their lips or clack their teeth to express

with others and even to manipulate them for his or her
own benefit—by trial and error, observation, imitation,
and practice. Young primates make mistakes along the
way, learning to modify their behavior based on the reac-
tions of other members of the group. Each member of the
community has a unique physical appearance and person-
ality. Youngsters learn to match their interactive behaviors
according to each individual’s social position and temper-
ament. Anatomical features common to all monkeys and
apes—such as a free upper lip (unlike lemurs and cats, for
example)—allow for varied facial expression, contribut-
ing to communication between individuals. Much of this
learning takes place through play.
For primate infants and juveniles, play is more than a
way to pass the hours. It is a vital means of finding out
about the environment, learning social skills, and testing a
variety of behaviors. Chimpanzee infants mimic the food-
getting activities of adults, “attack” dozing adults, and
“harass” adolescents. Observers have watched young go-
rillas do somersaults, wrestle, and play various organized

Figure 4.2 A long life cycle, including a long period of
childhood dependency, is characteristic of the primates. In
biological terms, infancy ends when young mammals are
weaned, and adulthood is defined as sexual maturation. In
many species, such as mice, animals become sexually mature
as soon as they are weaned. Among primates, a juvenile period
for social learning occurs between infancy and adulthood. For
humans, the biological definitions of infancy and adulthood are
modified according to cultural norms.

© Tim Davis/Corbis

Many ape nonverbal communications are easily recognized by

humans, as we share the same gestures.

3 18

Gestation in weeks

24 34 38

Mouse Lemur Macaque Chimp Human

80

70

60

50

40

30

20

10

5

Average life expectancy

in years

Prenatal period

Infantile period

Juvenile period

Adult period

Female reproductive period