McKay & Dennett (M&D) present a clever, substantive, and thought-provoking analysis of the evolution of mistaken beliefs. Unfortunately, we feel it falls short because it is based on a particular model of evolution that has limited applications for understanding the development of beliefs. Given that M&D are not estimating proportions of phenotypic variance attributable to genes versus environments and are rather trying to account for the origin of a system, the population genetic framework upon which they rely is not helpful. Because the population-genetic (“pop-gen”) framework does not speak to the development of organisms, it misconstrues the relationship between genes and behaviour (i.e., posits a passive conception of development), views beliefs as adaptations rather than as products of an organism's adaptability, and is blind to important epigenetic resources – most importantly in the case of the human belief system, language. We now expand upon these problems, and outline an alternative evolutionary developmental (“evo-devo”) perspective which would better ground evolutionary claims about beliefs.

We argue that belief in evolutionarily engineered, truth-aiming belief systems is a product of an inadequate pop-gen model of evolution that essentially ignores developmental processes (Callebaut et al. Reference Callebaut, Müller, Newman, Sansom and Brandon2007; Racine et al., forthcoming; Roberts Reference Robert2002; Wereha & Racine Reference Wereha and Racine2009). Stated simply, even if one considers that we have evolutionarily derived belief systems, these systems still have to emerge in ontogeny and are not fundamentally separate from developmental processes. Such an uncontroversial statement belies the different conceptualizations of development derived from the pop-gen and evo-devo models of evolution. The overextension of the pop-gen model into the organismic level of analysis leads to a passive characterization of development. That is, development is viewed as directed by a robust genetic system that uses the most minimal “environmental” input as a trigger. Therefore, M&D forgo a developmental analysis of belief when they describe the features of an “evolutionary belief system” by reverse-engineering the beliefs of adult humans. From an evo-devo perspective, collapsing complicated developmental processes to a genetic component terribly misconstrues the nature of development. Such a commitment to a mechanistic, genocentric view of evolution and a passive conception of development is inconsistent with a developmental perspective that emphasizes the ubiquity of multiple levels of influence beyond simply the genetic level (e.g., Gottlieb & Lickliter Reference Gottlieb and Lickliter2007). We now elaborate on how a narrow genocentric, non-developmental view has little use for understanding the formation of beliefs in humans, and demonstrate how radically different a developmental approach conceptualizes the issue. This difference is made explicit in describing the importance of “adaptive” and “adapted” in these two models.

In the context of their paper and in light of how these terms are used within the pop-gen model of evolution, it is understandable that M&D conflate the terms “adapted” and “adaptive” (see the target article's Note 3). We argue, however, that these two terms can actually characterize the difference between pop-gen and the developmental models of evolution. What are taken to be evolved belief systems or adaptations in the pop-gen model (genocentric view) are actually the products of organismic adaptability in an evo-devo perspective (organismic view).

In the pop-gen model, evolved belief systems are adaptations. Beliefs are “tools” derived from belief systems that were “engineered” by evolution (sect. 1). These systems, then, are conceived as features that organisms “acquire.” In this mechanistic, particulate, and additive genocentric conceptualization, belief systems are features that are in a way fundamentally separate from the organism and “used” by them. These systems (originating at the genetic level) were selected for because in our evolutionary past they conferred a differential reproductive advantage to their bearers (whether they led to the development of accurate representations of the world or not). From an evo-devo perspective, however, beliefs are viewed as products of organismic adaptability, not evolved adaptations. Adaptability is a property of organisms, not a property of any one part (adaptation). Further, beliefs are manifested at the organismic level, not at the genetic level. From this perspective, the ability to form beliefs may be conceived of as a fundamental property of complex organisms. It is not something that is “selected” for as something additional to the organism itself. It is an emergent product of animal biological systems and inherent in certain biological forms. It is based on a form of life that requires successful interaction with one's environment. Thus, at least the basis for “beliefs” is an intrinsic property of certain organisms, not a separate acquired adaptation.

The notion of evolved belief systems as adaptations, we argue, rests on a limited genocentric model of evolution and overused metaphor. “Belief systems” that exist as adaptations stem from using a population level of analysis to understand properties at the individual level. Because adaptability is an organismic property, its crucial importance in the development of belief is invisible to a genocentric view. An evo-devo conception of belief leads to understanding beliefs through developmental analysis rather than through genocentric, non-developmental “adaptational analysis.” At the very most, what can be “selected for” are perhaps particular refinements (mechanisms) within a “belief system,” not the belief system itself.

Elucidating the myriad factors that can affect development is integral in understanding how an organismic trait such as “beliefs” emerge. One obvious epigenetic resource is the complex rearing environment afforded to the developing human child, including human languages. Indeed, the forms of belief that M&D review emerge as functions and uses of complex forms of such languages. A developmental analysis of forms of belief along with linguistic competence in children is a necessary step to understanding the emergence of more complicated forms of belief through the lifespan. Further, if “language” itself is a crucial resource in such a system, M&D's postulation is strained by the fact that evolutionary pressures are seen to act over a very lengthy time period within a standard pop-gen framework.

Therefore, although we agree with M&D that accounting for the evolution of mistaken beliefs is an important task, we believe, hopefully not mistakenly, that it requires a much broader developmental conceptualization of evolution. In their response to commentaries, we encourage M&D to attempt to integrate their theory with recent work in evolutionary development psychology.