ABSTRACT
T here is a deep though largely unexplored schism in modern evo-lutionary thought over the nature of evolutionary functionalism. Differences reflecting this schism revolve around the question of what role present conditions as opposed to past conditions play in the functional explanation of a species' set of adaptations. Those who emphasize the role of ancestral conditions tend to focus on such concepts as design; adaptation; mechanism; fitness, as a property of a design or the genes underlying a design; histories of selection; complexity of functional design; standards of evidence for adaptations (such as efficiency, economy, and precision); the prevalence of species-typicality in complex functional design; the characterization of ancestral conditions or enviroI)ments of evolutionary adaptedness; and, most of all, the cause and effect relationship between ancestral conditions and present adaptations (see, e.g., Barkow 1984, 1989; Cosmides and Tooby 1987; Daly and Wilson 1988; Dawkins 1976, 1982, 1986; Toobyand Cosmides 1989a, 1989c; Williams 1966, 1985; see especially Symons 1987, 1989, 1990). Those who emphasize the role of the present tend to focus on adaptiveness; behavior; fitness, as the property of individuals; the aSsessment of fitness differentials between individuals; ongoing selection; individuals construed as inclusive fitness-maximizers or fitness-strivers; claims that contextually appropriate behavioral variation is driven by fitness-maximization; an antagonism to characterizing species-typicality (or even stable design) presented as a principled opposition to typological thinking; the present as the environment to which individuals are adapted; the fitness consequences of present behavior; and, most of all, the correspondence between present conditions and present fitness-maximizing behaviors (see, e.g., Alexander 1979a, 1979b, 1981; Betzig 1989; most of the articles
in Betzig,,_Borgerhoff Mulder and Turke 1988; Borgia 1989; Caro and BorgerhoffMulder 1987; Dunbar 1988; Hughes 1987; Smuts 1989). Although the literature cited deals largely with humans, where the debate is particularly active, it accurately reflects a division that extends throughout the community of behavioral ecologists, and, in fact, throughout biology as a whole. To identify these ideas as a single integrated viewpoint associated with specific individuals as if they were consistent exponents of one side of a binary debate would be a mistake, because nearly everyone in the evolutionary community employs, at one time or another, most of these common concepts for varied purposes. For example, Turke (1990) attempts to produce a hybrid of the two approaches, which starts out arguing for something resembling an adaptationist program, but ends up endorsing and practicing something closer to the second view. Leaving aside the question of within individual consistency, the ways in which these concepts are systematically used in evolutionary discourse add up to profoundly different visions of the role of the concept of functiqn in evolutionary biology. It is the validity of these alternative approaches to the concept of function, not the views of specific individuals, which is at issue. We will refer to the first approach as the adaptationist program and to the second approach as the correspondence or adaptiveness program (Symons 1990).
