An origin of reference in calls marking individual agents in social
interactions would associate an important attribute of language with the
general context of the evolution of intelligence in primates,namely,
sociality.As mentioned,monkeys and apes show more sophisticated skill
in social contexts than in solving problems with objects,and chimpanzees
are able to use objects as referential tokens within the confines of
language-teaching experiments.However,extrapolation of referential
meaning from the social context to the object world seems not to be
accomplished in the wild in any nonhuman primate.This limitation can
be explained by the social relations of both common chimpanzees and
bonobos.Common chimpanzee males associate closely with one another,
travel together in temporary parties,and form alliances.Females are
more likely to range alone with their dependent offspring,especially
during nonestrous periods. Cooperation and communication are
stronger and more sophisticated among males than either among females
or between males and females.Pant-hoot chorusing also occurs only
between males;females give this vocalization only rarely.
Although extensive cooperation exists between males,tool-using
behavior seems to be a female characteristic.Females use tools more
often than males,and,as Boesch and Boesch (1984) pointed out in the
case of Ivory Coast chimpanzees,most complex tool making is the exclu-
sive activity of females due to the strong male need to be together.
Division of activities between the sexes prevents communicative and
tool-using behaviors from being joined.
In contrast,bonobos tend to form more stable and larger mixed
parties,in which females are as likely to be found as males (Furuichi and
Ihobe 1994),due to famales’ extended sexual receptivity.Cooperative
actions between the sexes are frequent,and males even take part in
infant care.Accordingly,communication between males and females in
bonobos is more extensive than in common chimpanzees.Even the pant-
hoot analogue,the high hoot,is performed as a male-female duet.
Although the handicap resulting from divergence between coopera-
tion and tool making in the common chimpanzee is absent in bonobos,
the latter do not use tools in their natural habitat.Kano (1992),during
a ten-year study,observed only one case of using an object as a tool:a
branch with leaves was used as an umbrella.Living conditions in the
habitat of bonobos do not require,and consequently do not demand,use
of tools to obtain food.
Since linkage between sophisticated communication and object
manipulation is absent in both species,selective forces to imbue com-
municative signals with object-referential meaning are also absent.
Object-referent communication consequently has not evolved in either
species.130 Maria Ujhelyi