Darwin’s theory of evolution by natural selection has been phenomenally successful in providing a unifying framework, bringing together insights from a wide range of disciplines (physiology, development, and taxonomy, amongst others), and transforming our understanding of the biological world. Given this success, it is therefore tempting to attempt to expand the application of Darwin’s theory to domains outside of biology. In fact, this is the explicit motivation given by some cultural evolution theorists for the cultural evolution project as a whole. For example, Mesoudi and colleagues in a 2006 paper articulate the promise of the application of Darwinian theory to culture as the creation of a ‘cultural synthesis’ that mirrors what has been achieved in biology, with what they see as disparate and poorly understood cultural phenomena becoming unified under a broad evolutionary approach. Similarly, Muthukrishna and Henrich (2019, p. 223) suggest that dual inheritance theory could function as “a theory of human behaviour to unify the psychological and behavioural sciences”.
One way in which the debates over cultural selection have unfolded is in terms of the resemblance between cultural and natural selection. There are debates over whether cultural selection should be considered Darwinian or Lamarckian, due to phenomena such as guided variation (Kronfeldner 2007).Footnote 3 Additionally, as has been noted by many authors, key concepts in cultural selection do not have systematic definitions or solid theoretical grounding, such as cultural fitness, or the units of cultural selection (Wimsatt 1999; Crozier 2008). It is certainly the case that cultural systems bear many disanalogies with biological systems. However, I contend that focusing on the explanatory aptness or power of cultural selection provides a more fruitful avenue in assessing cultural selection frameworks compared to these debates about the strength of the analogy between culture and biology (although these debates have illuminated many important points of consideration).
Confusion or vagueness around core concepts in selection is not unique to culture: we see similar debates in the context of evolutionary biology over the appropriate fitness concept, or population concept, for example (Ariew and Ernst 2009; Stegenga 2014), or rethinking the necessity of reproduction, taken to be a core feature of populations that can undergo selection, as in Papale (2020). The lack of a single fitness or population concept has not hampered the capacity for natural selection to be a powerful explanation for organismal adaptation, amongst other phenomena, suggesting that this should not be a barrier for the application of cultural selection. For example, Ramsey and De Block (2017) note that cultural fitness concepts have real and substantial differences from biological fitness concepts. Nevertheless, they argue that we can build a concept of cultural fitness that can do the necessary work in feeding into cultural selection explanations.
I therefore focus on the explanatory payoffs of cultural selection: why are we applying it? What can we explain that we could not previously? For biological organisms, there are clear reasons to invoke natural selection. Darwin’s theory of evolution by natural selection provided a naturalistic explanation for the phenomenon of organisms appearing adapted to their environment, with a range of ingenious solutions to problems of survival (i.e., the appearance of design without the existence of a designer). One key aspect of the explanatory power of natural selection lies in its capacity to explain how features of organisms that appear designed to deal with specific challenges posed by their environment came about, without invoking intelligence or purpose within that explanation. As Nettle (2020, p. 2) notes, “the key insight of Darwinian genetic evolutionary theory was that design-like properties could be produced, over time, by selection processes. Thus, it is quite natural, seeing design-like properties in culture, to assume they must be produced by selection processes too”.
I argue that we should expect cultural selection frameworks to be able to do the same, explaining adaptive fit between cultural variants and environment without invoking intention or agency. Although selection plays other explanatory roles in biological systems, one distinctive role is that which it plays in explaining adaptation, or design. I use ‘adaptation’ as synonymous with ‘design’ here, adopting the definition given by Wertz and Moya (2019), in a paper which highlights the role that ‘design’ plays in cultural evolutionary theories, as a “structure that is well-suited to solve a problem”. As previously noted, we see ‘adaptive’ cultural traits, or those with the appearance of ‘design’, everywhere around us, if we construe ‘adaptive’ or ‘designed’ in this broad sense. This is the role that has been highlighted by several key figures in the cultural selection literature: cultural selection proponents often point to the capacity for cultural selection to explain ‘cultural adaptations’ (Richerson and Boyd 2005; Henrich and Henrich 2010; Boyd et al. 2011; Norenzayan et al. 2016; Kline et al. 2018). These adaptations, construed broadly as structures well-suited to solving a problem, could be at either the individual or the group level. Additionally, I use this broad definition to avoid assuming the truth of any particular account (cultural selection or intentional design) from the outset.Footnote 4
I will first clarify what is meant here by ‘explanation’ and ‘explanatory power’. I will then suggest that, while cultural selection accounts often are able to provide explanations of cultural phenomena, they sometimes lack explanatory power in comparison to other approaches. I defend this claim against two possible responses: that cultural selection can be explanatorily powerful even when it does not explain ‘design without a designer’ and that cultural selection can still be a useful framework even if it is not explanatorily powerful. I will elaborate on the strategy of comparing cultural selection to a goal-directed agent account in section ‘Contrasting cultural selection and goal‑directed agent explanations’.
Explanation and explanatory power
Although it is beyond the scope of this paper to explore in detail and defend a particular philosophical account of explanation, it is worth clarifying what it might mean for a cultural selection explanation to truly explain, or to be explanatorily powerful. There are two related considerations: firstly, whether a particular account constitutes a successful or adequate explanation, and secondly, the degree to which an explanation has explanatory power.
There are many accounts of scientific explanation; I will discuss briefly two of the most prominent. Under a causal account (such as Woodward 2005, 2010), broadly, an explanation involves making a counterfactual claim about the relationship between cause and effect: changing the cause would bring about a change in effect.Footnote 5Giving a causal explanation for a phenomenon is to specify the causal structure that is responsible for the production of the outcome. Therefore, to characterise an adaptive trait as the result of cultural selection would be to identify a selective process as the cause that is in some way responsible for the adaptive trait. This could be the distribution of the trait in the population (why the trait is widespread, or why some groups have this trait and not others), or the origin of the trait itself (understood in the sense outlined in Godfrey-Smith 2009, where successive rounds of selection can explain why a trait exists in its current form at all). In many of the cases that are characterised as instances of cultural selection, the intervention that would change the cause and search for a change in effect will have to be hypothetical, as, for example, in cultural group selection interpretations of the development of prosocial tendencies in early human societies. The construction of mathematical models provides one way in which these hypothetical interventions can be explored. However, there is a significant strand of experimental work which implements real-life interventions to study the relative impacts of selection and other features of cultural transmission (e.g., Acerbi and Tehrani 2018).
Under a unificationist account (such as Kitcher 1981), explanation means unifying a range of different phenomena. This is something that has clear relevance to cultural selection: authors have explicitly advocated for the ability for evolutionary approaches to culture to unify disparate cultural phenomena (Mesoudi et al. 2006). It certainly seems to be the case that cultural selection has more potential to unify phenomena than (for example) historical explanations, which may be highly local and contextual. If a range of apparently disconnected and very different cultural traits, such as food taboos in Fiji, incest avoidance practices, conservation laws, and the appeal of Kim Kardashian, could be explained through reference to the same process (selection), then under a unificationist account cultural selection seems like a successful explanation. However, it is important to be careful here: Kitcher’s account requires not only range (that the theory pertains to explananda across many domains) but also stringency. The stringency criterion means that explanations must also be restricted, and therefore be able to rule out explananda. This is to prevent explanations being vacuous. I suggest this is a tendency we see in the literature (made clearer by the case studies in section ‘Objections’): cultural selection has been applied in a multitude of contexts, but often at the expense of stringency.
The debates over the similarities or differences between cultural and biological systems have an important bearing on whether cultural selection can be considered an explanation at all. If it were the case that cultural selection cannot even get off the ground, i.e., that cultural systems are too dissimilar to biological systems in key respects, then clearly we can rule them out as explanations from the start. This kind of move has been made in the debate over memetics: critics have challenged the conceptual underpinnings of the research programme, such that we have prima facie reasons to dismiss memetic explanations out of hand, without consideration of particular cases or applications (an overview of these critiques can be found in Lewens 2018).
Regardless, I contend that the more common situation is one in which cultural selection can function as an explanation. In some cases, although cultural selection can explain, it can do so only weakly. This may be the more epistemically dangerous place to be: it is not that a cultural selection account leaps out as clearly unable to furnish explanation, but rather, that it appears to provide an explanation, without offering much in the way of explanatory power.
I draw on Schupbach and Sprenger’s (2011) account of explanatory power to flesh this out. The core of their account of explanatory power lies in the ability for a hypothesis to decrease the degree to which we find the explanandum surprising, or to increase the degree to which the explanandum is expected. They provide a “probabilistic logic of explanation that tells us the explanatory power of a theory (explanans) relative to some proposition (explanandum), given that that theory constitutes an explanation of that proposition” (p. 4). In the case of cultural selection, we can assume that the theory constitutes an explanation of a given phenomenon (in a causal, unificationist, or other sense), which we may often have reason to do. Nevertheless, we can assess its explanatory power, and compare this to competing alternatives.
When we consider explanations for ‘design without a designer’, we are assuming a highly ‘surprising’ explanandum. If cultural selection can decrease the extent to which ‘design without a designer’ is surprising, then this means this explanation has a lot of explanatory power. It certainly seems that cultural selection is capable of this: natural selection accomplishes this well, and cultural selection appears to be the right kind of mechanism that could generate this.
However, the question becomes whether the phenomenon in question is really ‘design without a designer’ or just ‘design’ (adaptive traits that could have been the product of intentional action). This is where the comparison with a goal-directed agent account comes in: if a goal-directed agent account can explain the adaptive trait, we can no longer characterise it as ‘design without a designer’. If that is the case, we are analysing the explanatory power of cultural selection in relation to ‘design’. In these cases cultural selection will have equal explanatory power, and perhaps less explanatory power, than goal-directed agent accounts. I suggest that if the goal-directed agent account and the cultural selection account have equal explanatory power, we should prefer the goal-directed agent account on the basis of plausibility (as elaborated on in the following section).
Other roles for cultural selection
One possible response would be to highlight the other roles that selection can play, other than explaining adaptation. For example, cultural selection could play a role in ‘distribution explanations’ (Neander 1995; Godfrey-Smith 2009). Perhaps this is not incompatible with an intentional, goal-directed agent account (this issue will be confronted in section ‘Defending the comparative strategy’). Particularly in cases where we have scant data, such as when reconstructing cultural trajectories in our evolutionary past, deploying cultural selection models could usefully illuminate features of cultural change. Cultural selection models could allow us to analyse patterns in the archaeological record and differentiate them from other processes, such as drift, thus providing an explanation for the spread of (for example) a particular kind of pottery throughout a population. This applies in particular to work within evolutionary archaeology (Lipo and Madsen 2001; Shennan 2020).
Whilst this response is persuasive, my argument would still mean a restriction in explanatory scope for cultural selection.Footnote 6I do not wish to deny the usefulness of these approaches. However, as previously highlighted, a key concern of the cultural selection literature are cultural adaptations. I take the analogy with biological selection to be useful here: if natural selection were unable to explain the complex and exquisite adaptations we see in the natural world (or were able to do so with no more explanatory power than a naïve goal-directed agent account, or another account we use intuitively and successfully every day), its explanatory scope would be clearly restricted. Claims regarding, for example, selection without reproduction, have often involved the question of whether selection in particular contexts is marginal, weak, or uninteresting, which is taken to mean the incapacity to act cumulatively to produce adaptation (Dawkins 1982; Godfrey-Smith 2009, 2012; Okasha 2006). Whilst cultural selection could play valuable roles in a variety of contexts other than explaining adaptation, nevertheless, adaptation is a central explanandum. Therefore, a strategy that helps to determine the contexts in which cultural selection can explain adaptation will have utility and will impact any general claims about the explanatory scope of cultural selection.
Alternatively, one could argue that cultural selection frameworks can still have value even if they do not provide increased explanatory power. We can see debates over a somewhat parallel claim in debates regarding niche construction. Some authors have argued for the value of niche construction as a framework for understanding biological phenomena. This is not because it is impossible to explain particular biological phenomena without invoking niche construction as a separate evolutionary process: indeed, opponents point out the capacity for standard approaches to explain the targets of niche construction (Scott-Phillips et al. 2014). However, its proponents maintain that recognition of niche construction as a distinct process could lead to attending to phenomena that were not attended to previously, and the development of explanations for these. Additionally, this approach could generate further insights into phenomena that are not captured well by a standard approach (Laland and Sterelny 2006; Uller and Helanterä 2017).
This response can be decomposed into two claims about the value of the niche construction framework. Firstly, niche construction can be said to have distinct heuristic value: it sets an agenda for research, directing researchers’ attention towards particular phenomena that were previously neglected. Secondly, thinking about certain phenomena in terms of niche construction may add new dimensions to our understanding, even if explanations can be formulated in terms of the standard approach. Similarly, in the case of cultural selection, one could argue that it has heuristic value. In section ‘Objections’ I will directly address this claim. I suggest that this is possible and would provide justification for adopting a cultural selection approach, although there are reasons to be skeptical about its heuristic value. Additionally, one could argue that cultural selection works at a different level of explanation. The objection of different levels of explanation is discussed in section ‘Objections’.
Although we would expect cultural selection to often constitute an explanation of a given cultural phenomenon, there are cases where cultural selection explanations will be weak and will not present increased explanatory power compared to alternative accounts.