INTRODUCTION

What is evolutionary psychology? The answer to this question is complicated by the fact that the term “evolutionary psychology” is commonly used in two distinct senses. In one sense, evolutionary psychology is simply the study of human behavior and psychology from an evolutionary perspective. In this sense, evolutionary psychology is a field of inquiry, a loose confederation of research programs that differ significantly in theoretical and methodological commitments. These diverse research programs attempt to explain a wide variety of phenomena, ranging from foraging and birth spacing in traditional hunter-gatherer societies to encephalization (the progressive increase in brain size relative to body size in the human lineage) and the evolution of altruism and language. What unites these research programs is not a shared commitment to specific theories regarding the evolution of human behavior and psychology, but only a commitment to articulating questions about human behavior and psychology, and articulating answers to those questions, with conceptual and theoretical tools drawn from evolutionary theory.