As I see it, evolutionary psychology is concerned with the problems and stresses our hominin and primate ancestors encountered in their environments, the psychological adaptations natural selection shaped to deal with these problems and stresses, and the way these adaptations function in the infinitesimal slices of evolutionary time in which we now live (Crawford & Anderson, 1989). Consider some examples. Obtaining sugar and fat were beneficial for our ancestors. Therefore, natural selection shaped psychological mechanisms in ways that rendered them tasty, and these adaptations, in turn, motivated our ancestors to take the risks and do the work needed to obtain them (Nesse & Williams, 1994). Adaptations designed to detect and punish cheaters evolved to help uphold the fitness-enhancing social contracts formed by early humans (Cosmides, 1989). Incest produced defective children. In response, natural selection designed mate-selection mechanisms that disposed humans to avoid mating with close kin (Shepher, 1983; Westermarck, 1891). The process was slow, but it shaped beings with a vast organization of interacting cognitive, emotional, and motivational mechanisms for interacting with each other and the physical and social environments in which their ancestors evolved. However, mechanisms that evolved to deal with ancestral problems may be produce unusual and possibly even maladaptive behaviors in some current environments (Crawford, 1998).