Information is a key resource for all animals because it permits choices to be made through learning. For the scientist, identifying social learning in noncaptive populations can be difficult. A focus on social information transfer, the criteria for which are more reliably measured in the field, may be preferable. A comparison of social information transfer in nonhuman primates and hominids reveals similarities and differences in two major realms: use of symbolic communication and the relative roles of immatures and adults in information transfer. Both nonhuman primates and hominids are capable of symbolic communication, although it is used in broader contexts, including material culture, in hominids. In monkeys and apes, immatures are themselves responsible to a great extent for obtaining information about critical survival skills. Adults, even parents, rarely intervene to aid or teach them. Humans actively "donate" information to immatures to a much greater degree than do nonhuman primates, Such active information transfer developed gradually during human evolution and occurred via outright teaching, sometimes via material culture such as tools and art; during leisure-time social interaction; and using many types of vocal production, not only full-blown speech. Differences in informationrelated abilities between nonhuman primates and hominids are quantitative rather than qualitative, but a significant product of human evolution is the ability and tendency to engage in active information transfer of all kinds.Reliance on shared information through networks of exchange and teaching is an important component of human culture. Indeed, some scholars define culture as a system of information or even as information itself (Barkow, 1989;Boyd and Richerson, 1985;Findlay and Lumsden, 1989). The evolution of the phenomenon of "social information transfer" is critical to a complete perspective on the evolution of human cognitive capacity (see Goodenough, 1990).In this paper I use a comparative framework to examine how information is exchanged among individuals in monkeys and apes, and among individuals and groups in hominids. Two patterns emerge from this comparison. First, in both nonhuman primates (hereafter primates) and hominids, individuals transfer information in a variety of ways, some of which indicate a capacity for symbolic communication. Symbolic communication is carried out mostly through use of the vocal-auditory channel in primates, and in broader contexts, including via material culture, in hominids. This finding opposes the tendency, still alive in anthropology, to conclude that primates communicate emotions and arousal states, and 0 1991 Alan R. Liss, Inc.
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YEARBOOK OF PHYSICAL ANTHROPOLOGY[Vol. 34, 1991 not specific information about the physical or social environment (Marler, 1985). Another tendency is to focus on the evolution of speech and language (Lyons, 1988) rather than on the gradual unfolding throughout human evolution of information transfer of all types, via behavior, vocal product...