How are we to understand the complex forces that shape human behav ior? A variety of diverse perspectives, drawing on studies of human behavioral ontogeny, as well as humanity's evolutionary heritage, seem to provide the best likelihood of success. It is in an attempt to synthesize such potentially disparate approaches to human development into an integrated whole that we undertake this series on the genesis of beh- ior. In many respects, the incredible burgeoning of research in child development over the last two decades or so seems like a thousand lines of inquiry spreading outward in an...