Epigenetic rules and Darwinian algorithms: The adaptive study of learning and development

Abstract Recent efforts toward a Darwinian psychology of human behavior will profit from taking account of prior investigations of proximate phenomena and adaptive mechanisms conducted within the science of biology, and from realizing that adaptive significance and underlying mechanisms must be investigated in concert. Contrary to some recent arguments, evidence of adaptive design is usually manifested initially and most prominently in the behavior (or other "ultimate" phenotypic expressions) of organisms, human or nonhuman, rather than in underlying psychological, physiological, or developmental mechanisms, which are often obscure, and in any case, as adaptive mechanisms, must be investigated secondarily. The reason is that selection acts most directly on behavior, and on its underlying mechanisms only as they influence the behavior. This is as true for learned and cultural behaviors as for any others. Adaptive significance of behavior, and evidence of its underlying design, is thus examined only by studying the behavior itself, its complexity, the situations in which it is expressed, and its effects in different situations. Biological mechanisms of any kind cannot even be identified with confidence, or understood, until, at the least, reasonable inferences have been made about their adaptive functions, what they are, as mechanisms, designed by selection to accomplish. Moreover, what appear to be adaptive psychological, physiological, or other mechanisms, may, as with some expressions of behavior, be incidental effects of still other mechanisms that are adaptive. Adaptation is not restricted to situations in which genes program specifically for particular behavioral alternatives: natural selection of alternative alleles may also yield abilities and tendencies to engage in conditional strategies, to assess costs and benefits in directly or indirectly reproductive terms. In humans, such cost-benefit assessments may be conducted entirely through mental scenario-building, or even through absorbing and judging the mental scenarios of others, without either admission or cognizance of the reproductive significance of the assessment. The goals actually sought may be secondary, tertiary, or even more distantly removed correlates of reproductive success (e.g., status or reputation, which may correlate with power, which may correlate with wealth, which may correlate with access to the resources of reproduction); reproductive success itself may be a concept alien to the actor's conscious motivations, even denied vehemently as a goal. In learned and cultural behaviors, selection has to be not only for the ability to learn but for its patterning, such as for the machinery enabling development of the ability to learn to make appropriate (cultural) decisions. Kin recognition is reviewed as the most prominent example of a set of extensively studied adaptive mechanisms involving learning, and as a central problem with respect to adaptiveness in social behavior. Arguments that the adaptive mechanisms collected under the concept of learning evolve as special, rather than general-purpose devices, raise provocative questions about the evolution of ontogenetic and physiological preparation to deal with environmental novelty, especially in complex social interactions. Evolution of the human psyche, especially its conscious aspects, is briefly discussed as a problem in understanding the history of sociality. It is argued that the principal environment of natural selection leading to the modern human psyche was social, and that on this account the environment of human behavior has not changed as much since the Pleistocene as is often assumed.