HOW ORGANISMS DO THE RIGHT THING - THE ATTRACTOR HYPOTHESIS

Neo-Darwinian theory is highly successful at explaining the emergence of adaptive traits over successive generations. However, there are rea sons to doubt its efficacy in explaining the observed, impressively de tailed adaptive responses of organisms to day-to-day changes in their surroundings. Also, the theory lacks a clear mechanism to account for both plasticity and canalization. In effect, there is a growing sentim ent that the neo-Darwinian paradigm is incomplete, that something more than genetic structure, mutation, genetic drift, and the action of na tural selection is required to explain organismal behavior. In this pa per we extend the view of organisms as complex self-organizing entitie s by arguing that basic physical laws, coupled with the acquisitive na ture of makes adaptation all but tautological.'That is: much adaptatio n is an unavoidable emergent property of organisms' complexity and, to some 2 significant degree, occurs quite independently of genomic chan ges wrought by natural selection. For reasons that will become obvious , we refer to this assertion as the attractor hypothesis. The argument s also clarify the concept of ''adaptation.'' Adaptation across genera tions, by natural selection, equates to the (game theoretic) maximizat ion of fitness (the success with which one individual produces more in dividuals), while self-organizing based adaptation, within generations , equates to energetic efficiency and the matching of intake and biosy nthesis to need. Finally, we discuss implications of the attractor hyp othesis for a wide variety of genetical and physiological phenomena, i ncluding genetic architecture, directed mutation, genetic imprinting, paramutation, hormesis, plasticity, optimality theory, genotype-phenot ype linkage and puncuated equilibrium, and present suggestions for tes ts of the hypothesis. (C) 1998 American Institute of Physics.