Introduction

In this volume and in related publications, various authors have presented a rich and heterogeneous array of hunches and hypotheses about the possible mechanisms of self-awareness, and their ontogeny and evolution. Some of these are full-blown theories, others are presented merely as intuitions. In this last chapter we take on the task of identifying, classifying, and comparing these diverse and often contradictory models. For clarity, we organize our review and evaluation, following Tinbergen (1963) and others (Hinde, 1982; Yoerg & Kamil, 1990), according to four approaches to the study of evolved behavioral capacities: their proximate or immediate causation (physiological, information processing, or psychological mechanisms or organizing principles), ontogeny, specific evolutionary history in a particular lineage, and adaptive functions in various species. A full evolutionary explanation should embrace all four approaches.

These four approaches focus on complexly interrelated facets of behavior: The proximate mechanisms and ontogeny of behaviors in each lineage have been favored by a specific history of selective and random forces and developmental constraints operating on a set of preexisting mechanisms and developmental patterns. Specific mechanisms and their development have been favored because they met certain selection pressures present in other members of that lineage at the time these mechanisms evolved. Similar functional systems based on different mechanisms and developmental patterns have often evolved independently in distantly related species with differing histories and distinct preexisting complexes because they met similar selection pressures.