The so-called by-product explanations of morality have been presented as an alternative to adaptationist accounts (Prinz 2009). According to Prinz, since there is no mental mechanism dedicated to the acquisition of moral norms, the fact that we make moral judgments is not an adaptation but an evolutionary accident, i.e. a by-product of capacities evolved for other purposes. According to Fraser (2010) Prinz’s stance is not inconsistent with an adaptationist account of the evolution of morality. Fraser argues that morality may be, rather than an accident, a secondary adaptation, that is an exaptation, consisting in the cooptation for a new purpose of a structure initially served other functions or none (Gould & Vrba, 1982). Thus, Fraser seems to reconcile the lack of a moral machinery with a description of morality as adaptation: that is, capacities evolved for other purpose(s) (e.g., emotional bonds with kin) have been selected for a different one (e.g., promoting cooperation between non-kin). My point is that the trouble lies inside the nature of adaptation, and it is deeper than the mere semantic question that the same trait could be defined both as adaptation or exaptation depending on which function – past or present – we are referring to. The core of exaptation is not the epistemological claim that it is difficult to tell whether a trait is an adaptation or not, but rather the “ontological objection” that most traits are not adaptations (Dupré 2002). In this sense, we cannot legitimately describe morality as adaptation (Fraser 2010). It seems more appropriate to interpret morality as a by-product only in the sense of being a contingent epiphenomenon that other adaptive mechanisms or building features make possible, not inevitable.
Dupré J. (2002), Ontology is the problem, Behavioral and Brain Sciences, 25-4, pp. 516–517.
Fraser B. (2010), Adaptation, exaptation, by-products and spandrels in evolutionary explanations of morality, Biological Theory, 5-3, pp. 223–227.
Gould, S.J. & Vrba, E.S. (1982) Exaptation- A Missing Term in the Science of Form. Paleobiology, 8, 1: 4-15.
Prinz J. (2009), Against moral nativism, in Bishop M., Murphy D. (eds.), Stich and his critics, Wiley-Blackwell, pp. 167– 189.