Tool evolution follows Darwinian principles: tools are phenotypes replicated through socially transmitted building instructions, modified by selection for human needs. The ostensive triangle—a pointer, an observer, and an object—enables social transmission of motor-act sequences that replicate tools for convenience or fitness rewards. Tools synchronize perceptions, create psychological understanding, and reshape social networks. Massive tool fabrication has accelerated prosociality and the development of a third-person perspective. This cumulative cultural evolution, entangled with biological evolution, selected traits that enhance social transmission, making tool evolution and individual instructional content prerequisites for higher cognition and consciousness.
Phencyclidine (PCP) produces effects in rats that resemble both positive and negative symptoms of schizophrenia. In the social interaction test, PCP dose-dependently caused stereotyped behavior and social withdrawal. Antipsychotic drugs selectively reduced these PCP-induced behaviors, while non-antipsychotic drugs did not. These findings suggest that PCP effects in the rat social interaction test may serve as a model of schizophrenia symptoms with face and predictive validity, useful for testing new antipsychotic compounds.