In recent years something of a divide has arisen in theoretical evolutionary biology. On the one side are those who argue that standard, gene-centric evolutionary theory is, in one way or another, incomplete or otherwise unsatisfactory (Laland et al. Reference Laland, Odling-Smee, Feldman and Kendal2009; Pigliucci & Müller Reference Pigliucci and Müller2010; Wilson & Wilson Reference Wilson and Wilson2007). On the other side are the silent majority of evolutionary biologists, who continue to work, productively, with standard evolutionary theory, and do not see any particular reason for change. As critics of orthodox theory acknowledge, “The commonest reaction to our explanations is something along the lines of ‘But that is already understood as part of the Modern Synthesis anyway’” (Pigliucci & Müller Reference Pigliucci and Müller2010, p. 4).

The revolutionary position has, however, received slightly wider acceptance within one particular community: evolutionary perspectives on humans and human behaviour. This is not to say that standard, gene-centric evolutionary theory has been rejected by that community. On the contrary, many researchers continue to use it, and the literature includes vigorous defenses of it, and criticism of the purported alternatives (e.g. Dickins & Rahman Reference Dickins and Rahman2012; Pinker Reference Pinker2012; Scott-Phillips et al. Reference Scott-Phillips, Dickins and West2011; West et al. Reference West, El Mouden and Gardner2011). Nevertheless, there is a sizeable group of researchers in this area that have been persuaded that orthodox evolutionary biology does not on its own provide a sound theoretical basis for the evolutionary study of human behaviour, culture, and society (e.g. Laland et al. Reference Laland, Kendal and Brown2007; Richerson & Boyd Reference Richerson and Boyd2005; Wilson & Sober Reference Wilson and Sober1994). As a result, “the sharpest divide between evolutionary students of human social behavior is between … Strict Neo-Darwinians and Expanded Synthesis Evolutionists” (Richerson Reference Richerson2012).

There is now a sizeable literature built around this partial rejection of evolutionary orthodoxy. In particular, there are considerable bodies of work that argue: (i) that the evolution of many human social behaviours is best explained in terms of cultural multilevel selection (despite the fact that there is no formal justification to consider the cultural group as a unit of selection [Gardner & Grafen Reference Gardner and Grafen2009; West et al. Reference West, El Mouden and Gardner2011]); and (ii) that cultural evolution and other forms of extra-genetic inheritance change the Darwinian process to such an extent that they render orthodox evolutionary theory ill-suited for the study of humans, human behavior, and human culture, and hence that its utility in this domain is limited, perhaps only to special, idealized cases.

Smaldino's target article implicitly accepts these arguments as a premise, poses a new question for them (How can we explain group-level traits?), and, within this framework, considers some possible approaches and answers to that question. It thus almost ignores more orthodox evolutionary theory, in which culture is a proximate mechanism (but not “just” or “merely” a proximate mechanism), and approaches to cultural evolution and group-level phenomena that have been developed within this orthodox perspective. Some of this work is extremely relevant to Smaldino's questions, and indeed even provides some answers, yet it is not at all cited. By way of illustration, we here highlight two examples. There are others, but we have only limited space.

The first is the work of cultural epidemiologists, who have developed a rich literature of both theory and data to explain the existence and emergence of group-level traits. In this framework, the spread of cultural traits through a population is explained by the fit of the trait to the natural dispositions of the human mind (or the local cultural ecology), just as parasites spread to the extent that they fit the natural physiologies of host organisms (Sperber Reference Sperber1996). By virtue of this process, cultural traits gravitate towards certain forms (called “attractors”) and away from others (Sperber & Hirschfeld Reference Sperber and Hirschfeld2004). As such, this research agenda explains culture in terms of its fit with the natural, evolved dispositions of the human mind, and in doing links cultural evolution with standard evolutionary approaches to human psychology. This approach has been successfully used to study the emergence of numerous cultural traits, such as religious beliefs, kinship systems, legal norms, and others, which are variously either the sort of group-level traits that Smaldino is interested in, or the institutions that give rise to them (e.g., Atran & Norenzayan Reference Atran and Norenzayan2004; Bloch & Sperber Reference Bloch and Sperber2002; Boyer & Petersen Reference Boyer and Petersen2012). Either way, cultural epidemiology has a great deal to offer Smaldino, but his target article does not make use of it.

The second example of research that can potentially address some of the issues raised in the target article, but from a more orthodox perspective, is the psychology of individual differences (Nettle Reference Nettle, Dunbar and Barrett2007). One hypothesis, which follows from and is productively studied within standard evolutionary theory, is that individual differences (in, e.g., personality, intelligence, neuroticism, and so on) are adapted, niche-specific life-history strategies, and can be the product of an individual plasticity that has been selected in order to maximise inclusive fitness across varied environments (Buss & Greiling Reference Buss and Greiling1999; Nettle Reference Nettle2006). The growing importance of group living in human evolution will have brought with it trade-offs around competition for resources, and with it sufficient pressure for selection of niche-specific life history strategies; in other words, individual differences. Division of labour within the group, becoming a specialist within the group structure, could readily act to maximize individual fitness, but the cost would be the loss of possible independence should the group disintegrate. A snapshot observation of this structure might subsequently lead an observer to conclude the group has emergent properties. However, the ultimate causal explanation would still be the individual maximization of inclusive fitness, as elaborated by standard evolutionary theory.

In sum, because Smaldino has chosen to conduct his discussion almost entirely within the context of a literature that has rejected at least part of orthodox theory, the target article fails to recognise that there are other literatures that potentially offer simple, elegant explanations of the phenomenon it is concerned with. In fact, we think it quite possible that the integration of the two areas we explicitly mention above could provide an extremely rich, synthetic explanation of group-level traits, but this possibility is not entertained. On the contrary, the very existence of alternative, orthodox ways of thinking about the topic at hand is not even mentioned.

Smaldino asserts that “an evolutionary theory of culture is here to stay” (sect. 1, para. 1). We agree, and welcome this. However, there is no good reason why that theory can or should ignore other existing, productive, and more evolutionarily orthodox literatures, especially those that have much to say about the concerns of cultural evolution theorists. (This is true even if we put to one side the question of whether the partial rejection of evolutionary orthodoxy that exists in much of the cultural evolution literature is justified.) Indeed, these other literatures have made and tested a number of explicit predictions about group-level traits and/or closely associated phenomena. In contrast, exactly what predictions follow from Smaldino's analysis is not clear.