"This reviewer had to be restrained from stopping people in the street to urge them to read it: They would learn something of the way science is done,...

The scientific, ethical, and policy issues raised by research involving the engraftment of human neural stem cells into the brains of nonhuman primates are explored by an interdisciplinary working group in this Policy Forum. The authors consider the possibility that this research might alter the cognitive capacities of recipient great apes and monkeys, with potential significance for their moral status.

Primate vocal communication is very different from human language. Differences are most pronounced in call production. Differences in production have been overemphasized, however, and distracted attention from the information that primates acquire when they hear vocalizations. In perception and cognition, continuities with language are more apparent. We suggest that natural selection has favored nonhuman primates who, upon hearing vocalizations, form mental representations of other individuals, their relationships, and their motives. This social knowledge constitutes a discrete, combinatorial system that shares several (...) features with language. It is probably a general primate characteristic whose appearance pre-dates the evolution of spoken language in our hominid ancestors. The prior evolution of social cognition created individuals who were preadapted to develop language. Several features thought to be unique to language—like discrete combinatorics and the encoding of propositional information—were not introduced by language. They arose, instead, because understanding social life and predicting others’ behavior requires a particular style of thinking. (shrink)

Among monkeys and apes, both the recognition and classification of individuals and the recognition and classification of vocalizations constitute discrete combinatorial systems. One system maps onto the other, suggesting that during human evolution kinship classifications and language shared a common cognitive precursor.