Contemporary theories of cultural evolution

By Stefan Linquist
To appear in Ashgate Series in Evolutionary Thought: The Evolution of Culture,
Ed. Stefan Linquist. Ashgate Press.

    
    Sections
     1.  Introduction
     2. Theoretical Background.
     3. The Phylogenetic Approach to Cultural Evolution.
     4. Memetics.
     5. Dual lnhertiance Theory and Niche Construction.
     6. Psychological mechanisms.
     7. Culture in Non-human Animals. 
     8. Bibliography.

1. Introduction      Recent decades have seen a renaissance in the study of culture from an evolutionary perspective. Since the early 1970s at least four theoretical frameworks have emerged that apply evolutionary concepts and models to cultural phenomena. This family of theories bears little resemblance to earlier, teleological accounts of cultural evolution that originated with Herbert Spencer and flourished during the late 19th and early 20th centuries. Gone is the notion that societies can be ranked on a scale from “primitive” to “advanced” or the idea that cultural evolution requires technological or moral progress. Instead, contemporary accounts of cultural evolution are an extension of the same Darwinian tradition that informs the biological sciences. At the heart of this tradition are two principles that transformed prior conceptions about the nature of biological diversity. The first principle states that all earthly life forms share a common ancestor and are thereby related by descent. This insight gave birth to a new way of thinking about organisms and their parts. After Darwin, species were no longer seen as immutable types but instead as interbreeding lineages whose features are continually reshaped by changing environments. The second principle states that adaptiveness (i.e. the functional suitability of a species to its environment) arises automatically out of the inter-generational reoccurrence of variation, heritability and differential fitness. This is Darwin’s principle of natural selection. Just as these two principles have revolutionized the study of biological diversity they are now having a similar impact on the study of culture. Recent Darwinian approaches to culture endorse (to varying degrees) the following two versions of these principles: 1)      The principle of cultural descent: All human cultures share a common ancestor and are related by descent. Just as certain genetic and morphological structures are preserved among related organisms over successive generations, certain cultural traditions (e.g. beliefs, values, skills and tools) are preserved with fairly high fidelity as they are socially transmitted from individual to individual. 2)      The principle of cultural selection: Cultures adapt to local ecological and social conditions by a process of variation, heritability and differential fitness that is akin to natural selection.  Although these principles constitute the core assumptions of contemporary Darwinian approaches to culture, each member in this family places a unique spin on their meaning and significance. The phylogenetic approach (Chapter 2) prioritizes the principle of cultural descent, applying to cultural groups the same methods used in reconstructing ancestral relationships among species. Meme theory (Chapter 3) places greater emphasis on the principle of cultural selection, viewing individual concepts or “memes” as gene-like replicators that compete for control over human thought and behaviour. Dual inheritance theory (Chapter 4) views culture as a second inheritance system that interacts with genetic evolution. Finally, niche construction theory (Chapter 4) explores the ways that humans use culture to modify and adapt to their environments.  Proponents of these four approaches are engaged in ongoing debates over a set of key issues. For example, what are the units of cultural evolution? To what extent is cultural evolution constrained by genetic evolution? Is culture transmitted in fairly cohesive ‘chunks’ or are individual beliefs, norms, skills, etc. transmitted independently of one another? To what extent is culture transmitted horizontally (from individual to unrelated individual) and what does this imply about the biological cost and benefits of culture? Such questions are internal to the Darwinian tradition insofar as they accept the two central principles of cultural descent and cultural selection (although they sometimes disagree over the details). Many of the articles contained in this volume are concerned with just these sorts of internal questions. Another set of external challenges question one or both of these principles. For example, a standard objection to the principle of cultural descent argues that cultural transmission is such a low fidelity process that, unlike genes or traits, there is no stable cultural entity that can be identified as a unit of evolutionary change. Another objection, directed more at the principle of cultural selection, states that concepts, beliefs and other cultural phenomena do not undergo variation and differential selection. Debates over these external challenges play out in different ways depending on which of the four perspectives one is considering (see below). In addition to these internal and external challenges, Darwinian approaches to culture encounter a third set of boundary issues concerning their relationship to neighboring disciplines. One such issue is whether evolutionary accounts of cultural change conflict with non-Darwinian explanations offered by historians and anthropologists. It is often assumed that the Darwinian approach to culture undermines the standard model of explanation embraced within the social sciences (Barkow, Cosmides and Tooby, 1992). This assumption has led some social scientists to adopt a defensive stance towards theories of cultural evolution, focusing more on their limitations than on ways that those theories might be improved. However, it is often not clear whether Darwinian explanations do in fact conflict with historical or anthropological accounts of cultural change. This is issue is addressed in the theoretical background section of this introduction and in Chapter 1 (see also Laland and Brown, 2002; Mesoudi, Whiten and Laland, 2006). Other boundary issues arise at the interface between cultural evolution and empirical psychology. Typically, cultural evolutionists operate with a fairly thin description of the human mind. For example, a key theoretical concept in memetics is the idea of a “meme filter”. This psychological mechanism supposedly favors certain cultural variants over others and, in so doing, imposes a kind of selection pressure on memes. But it is not clear how this theoretical construct might be cashed out in psychological terms. This issue is discussed in more detail in what follows in the context of meme theory (see chapter 3 and discussion below). Another boundary dispute between cultural evolution and empirical psychology concerns the extent to which culture is innately specified. Some critics of the Darwinian approach argue that it cannot explain the tendency for cultural representations to remain stable over successive generations. In particular, this objection has been raised by evolutionary psychologists who argue that if culture was transmitted primarily by social learning, as proponents of the Darwinian approach assume, then cultural traditions would rapidly degrade (Atran, Chapter 3; Sperber and Hirshfeld, Chpater 5). Thus, evolutionary psychologists offer an alternative perspective that views culture as the product of an innate psychological architecture. Such boundary disputes between cultural evolution and empirical psychology are discussed in Chapter 5 and in what follows. Finally, many of the theories discussed in this volume push the boundaries of our traditional concept of culture. It is often assumed that humans are a uniquely cultural species and, indeed, that it is culture which makes us ‘special’. This view is challenged by the view that culture is simply socially transmitted information which, it turns out, is found in many species besides our own. Hence, another sort of boundary dispute concerns whether human culture is unique, and the extent to which it obeys the same evolutionary principles as culture in non-human animals. These issues are addressed in Chapter 6 and below. Each section of this introduction offers a fairly self contained summary of the six chapters in this volume. As with any collection of its breadth, a considerable amount of hand wringing went into the selection process. Many significant publications had to be passed over because they are too technical for an introductory audience. Others were excluded simply because they already appear in existing collections. However the articles that do appear in this volume offer, I think, a fairly balanced and comprehensive representation of recent trends in the study of cultural evolution. (Back to Sections Menu)

2. Theoretical Background.       Darwinian theories of cultural evolution are relative newcomers to the intellectual landscape and their reception, especially within the social sciences, hasn’t been overly enthusiastic. One reason why Darwinian theories of culture have encountered resistance is because of their association with previous, unsophisticated theories of human nature. The teleological theories of Spencer and his followers were not only misguided, they easily lent themselves to racist and imperialistic doctrines. More recently, the Sociobiology movement of the early 1970s further contributed to Darwinism’s bad name. Sociobiologists attempted to explain a broad spectrum of human behaviour as evolving by natural selection to promote inclusive (genetic) fitness. Everything from human mating preferences to the determinants of social status have been interpreted by sociobiologists as serving individual genetic interests. This emphasis on cross-cultural universality and the related idea that genes keep culture on a “short leash” did not sit well with cultural anthropologists, many of whom were familiar with the diverse forms that human culture can take and with the central role of social learning in human development.  (See Laland and Brown, 2002 for an excellent discussion of the Sociobiology movement and its influences on evolutionary approaches to culture).  Proponents of modern Darwinian approaches to culture have therefore made an effort to distance themselves from the core assumptions Sociobiology. This concern is reflected in several of the articles appearing in Chapter 1 of this volume. For example, F.T Cloak (1975) emphasizes that a theory of cultural evolution must take into account the influence of learning constraints and social institutions on the direction of cultural change. Cloak also appears to have been the first to recognize that since cultural information is capable of rapid inter-organismic transmission (spreading, he notes, like a virus), culture will sometimes evolve in ways that are irrelevant or even destructive to the individuals who propagate them (the “virus-like” nature of culture was later seized upon and publicized by Richard Dawkins, and now forms one of the central tenets of meme theory). Although some of these principles have been developed considerably since the publication of Cloak’s article, many of his pioneering ideas remain worthy of attention. The articles by Luigi Cavalli-Sforsa and William Durham advance a similar line of argument: Darwinian theories of cultural evolution address the origin and causes of cultural diversity – they in no way ignore it—and doing so requires making a distinction between cultural and genetic evolution. Written only a decade or so after Cloak’s influential article, these papers document the considerable amount of development that Darwinian theories of culture underwent during this productive period.  The fourth article in this chapter offers a more skeptical assessment of recent theories of cultural evolution. Historian Joseph Fracchia and well known evolutionary biologist Richard Lewontin argue that theories of cultural evolution lack the resources for explaining cultural change. These authors assume that evolutionary explanations of culture are either selectionist in nature (that is, they explain cultural change in terms of the principle of cultural selection) or else they are indistinguishable from standard historical explanations. The problem with selectionist explanations of culture, they argue, is that they adopt a “variational scheme” – cultural change is attributed to variation and differential fitness among individual cultural variants. Fracchia and Lewontin note that many cultural changes do not follow this pattern of blind variation and selection.  For example, historians sometimes appeal to things like a sense of national pride or cultural ethos when explaining why events unfold in particular ways and not others. Fracchia and Lewonton’s central argument is that these sorts of explanations, which appeal to shared cultural representations and communal goals, cannot be reduced to the variation and differential spread of ideas.  A detailed treatment of Fraccia and Lewontin’s argument is beyond the scope of this introduction. In fact, most of the papers contained in this volume either expand on features this argument or attempt to demonstrate why it is flawed. (Of particular interest are the articles contained in Chapter 2 where the phylogenetic analysis of culture is defended. These papers demonstrate that not all evolutionary explanations of culture are selectionist in character.)  Rather than attempting to survey all of the issues raised by the articles appearing in this theoretical background chapter, the remainder of this section focuses on three common issues: (1) how should “cultural evolution” be defined? (2) what are the units of cultural evolution? and (3) how is cultural selection akin to natural selection?  A brief review of these general questions will set the stage for more specific topics addressed in following chapters.                 1.1 Defining “cultural evolution”.       Many researchers consider it important at the outset of an investigation to precisely define their subject matter. This is a challenging task in the study of cultural evolution because both “culture” and “evolution” are vague and ambiguous terms. The concept of culture operative within the social sciences is what philosophers would call a ‘family resemblance’ concept: it refers to a broad range of practices, traditions, artifacts and beliefs that exhibit some overlapping similarities, but which do not share an essential set of defining characteristics. Some cultural phenomena, like novel works of art, probably do not lend themselves to an evolutionary analysis. While other cultural practices, like tool making or language, are especially good candidates for an evolutionary investigation. The term “evolution” is problematic for a different reason. In common parlance, “evolution” often connotes progressive change towards some end or goal. Biologists have made an effort to strip the term of such teleological implications. However, the standard textbook definition of evolution as a change in gene frequencies over successive generations is obviously too narrow for theories of cultural evolution, and arguably too narrow for biology. An alternative definition of “evolution” as descent with modification, though vague, is perhaps better suited to current purposes. This phrase captures what is essential to most of the objects that evolutionary theorists study: these are entities (in a loose sense of the term) that preserve many of their features as they are transmitted from individual to individual, but which undergo slight modifications in structure that are retained and become salient over large time scales. Importantly, evolution is not to be confused with the Darwinian mechanism of natural or cultural selection. Selection – which involves variation, heritability and differential fitness —is just one of several mechanisms that can drive the evolutionary process.    Ideally, it would be possible to specify from the outset which sorts of cultural phenomena admit of an evolutionary analysis and which ones do not. However, as Cavalla-Sforza notes (1986), attempting to define the scope of evolutionary theories of culture would be premature at this early stage of their development. A more productive strategy is to begin with a vague definition of culture that captures a range of cultural phenomena that lend themselves to an evolutionary analysis. This definition can then be refined as the discipline matures. To this end, Cavalli-Sforza defines culture as the range of phenomena that involve learning and transmission. He clarifies this working definition to some extent by providing prototypical examples of culture found in both human and non-human organisms.                     F.T Cloak (1978) points out that “culture” is used ambiguously to refer both to the set of internal mental instructions that guide behaviour (“i-culture,” as he calls it) and also to the set of material artifacts, social relations and institutions that reside outside the individual mind (or “m-culture”). These two forms of culture interact in several ways. I-culture both propagates itself from individual to individual and tends to give rise to m-culture. In turn, m-culture influences the development of both i-culture and on other m-cultural artifacts. However, Cloak argues that, from an evolutionary perspective, i-culture is more fundamental than m-culture. Although i-culture is capable of replicating itself without m-culture, he claims, m-culture requires i-culture to persist indefinitely. For example, a clay pot will degrade and disappear over time, but the instructions for making pots can survive indefinitely. Cloak concludes that m-culture will tend to evolve in ways that promote the spread and maintenance of i-culture, but not vise versa. Thus, in order to identify the evolved function of a tool or piece of pottery it is necessary, on this view, to determine how these artifacts contribute to the maintenance and spread of the instructions that code for their production. On this view, artifacts have the evolved function of promoting the instructions that generate them in the same way that, according to some evolutionary biologists, phenotypic traits have the function of propagating the genes that contribute to their development (Williams, 1966; Dawkins, 1978). In drawing this distinction between i-culture and m-culture, Cloak appears to be searching for something within the domain of culture that corresponds to the genotype/phenotype distinction in biology. He also accepts uncritically the view that packets of information and not their physical manifestations are the ‘fundamental units’ of evolution. According to this line of reasoning, an entity must be capable of surviving indefinitely in order to qualify as a unit of evolution (Williams, 1966). Information encoded either in genes or mental instructions are supposedly ‘immortal’ while the physical products of information, like phenotypic traits or material artifacts, are considered ephemeral.  This argument touches on a controversial subject within evolutionary biology that is too involved to discuss here (see Sterelny and Griffiths, 1999). Restricting ourselves to cultural phenomena, however, the claim that all forms of i-culture can persist indefinitely without m-cultural manifestations is mistaken. It is hard to imagine how one would convey certain tool making strategies or pottery techniques without constructing one of these artifacts. Nor, for that matter, is it likely that someone could glean the requisite craftsmanship from just a close inspection of the finished products. Rather, it appears that both i-culture and m-culture play essential, reinforcing roles in the maintenance and propagation of certain traditions. Contrary to Cloak’s claim, neither type of culture necessarily evolves to promote the propagation and maintenance of the other. 1.2 The units of cultural evolution.            The previous subsection hit on a question that is often raised in the context of evolutionary theories of culture: what are the objects or ‘units’ that evolve by cultural evolution? As Cavalli-Sforza notes, it is extremely difficult to identify a cultural unit of transmissible information that corresponds to the biologist’s favorite unit of evolution: the gene. What cultural evolutionists are apparently looking for is something that is both preserved with high fidelity across generations and which is capable of undergoing something akin to genetic mutations. Most often, cultural evolutionists will speak of ideas or “memes” (as Richard Dawkins has dubbed them) as the units of cultural evolution. However, we have already seen that mental states are not the only sorts of cultural entities that undergo descent with modification – cultural artifacts evolve as well. Moreover, it is often difficult in practice to tease apart the respective roles that material artifacts and ideas or memes play in their continued maintenance and propagation. Some cultural evolutionists adopt the more neutral term “cultural variant” to describe the vast range of entities capable of undergoing cultural evolution (Boyd and Richerson, 1985). It remains to be seen whether this concept can be further refined to provide a cultural analogue to the evolutionary gene, or, indeed, whether identifying such an entity is important for developing a theory of cultural evolution (see Chapter 3 and discussion of memetics below). For purposes of clarity, throughout this introduction the term “tradition” will be used when speaking in general terms about material objects, mental representations or social practices that are structured primarily by culturally transmitted information. The word “trait” will be reserved for objects representations or social practices that are influenced primarily by biologically (e.g. genetically) transmitted information. Note however that these are not exclusive categories. The development of many behavioural dispositions, for example, involves both genetically and culturally transmitted information.   1.3 Cultural transmission and cultural selection.      There are some obvious differences between the ways that biological and cultural information gets passed on. Since traits are inherited genetically they are restricted to a vertical mode of transmission (from parent to offspring). This constraint limits the rate at which traits can evolve. Cultural traditions, by contrast, are potentially also transmitted horizontally (from individual to unrelated individual in the same generation) or obliquely (from an individual in the n generation to unrelated individual in the n+1 generation). These additional transmission pathways influence the rates at which culture evolves. As Cavalli-Sforza explains (Chapter 1), cultural traditions evolve most rapidly when they are transmitted horizontally from one-to-many individuals. However, horizontal transmission can also retard the rate of cultural evolution, such as when a tradition is transmitted non-vertically from many-to-one. Traditions that are enforced by peer pressure (e.g. etiquette norms) are likely to follow this pattern. The fact that traditions can spread horizontally and obliquely also allows for the evolution of maladaptive behaviours. A behaviour is maladaptive when it decreases the reproductive fitness of its bearer in comparison to some alternative course of action. Enforcement of the one-child policy in some cultures is an example of a horizontally transmitted tradition with maladaptive consequences.             Such talk of traditions that are favored by one’s cultural circumstances but maladaptive at the biological level can generate confusion, especially when it comes to distinguishing cultural transmission from cultural selection. In biology, heritability (or parent-offspring transmission) is just one component of natural selection. For natural selection to occur there must also be variation and differential fitness among traits. However, in cultural evolution theory the distinction between transmission and selection is often blurred. Consider a tradition that spreads rapidly through a population because of its obvious utility, such as the controlled use of fire. Should we say that this tradition is favored by cultural selection?  Or, is the increase in popularity due to what some theorists call a “transmission bias”?  What, if anything is the difference between these two characterizations?  To make matters more complicated, a tradition like this one will undoubtedly enhance the reproductive fitness of those who adopt it. Assuming that fire making techniques are passed on from parent to offspring, their increase in frequency will therefore be driven to some extent by natural selection in addition to cultural factors.    A certain amount of progress could be achieved in this domain if cultural evolution theorists could agree on a single conceptual framework for categorizing cultural phenomena. Unfortunately, different theorists currently use “transmission”, “cultural selection”, and “learning bias” to describe different sorts of processes. Perhaps the simplest option is to abandon the analogy between cultural and natural selection and view culture strictly as a mechanism for transmitting information (Boyd and Richerson, 1985). On this view, selection occurs only at the biological level, namely, when a behaviour (influenced either by culturally or genetically inherited information, or both) impacts the reproductive output of its bearer. In some cases selection will be the primary force driving the spread of a behaviour, such as when an adaptive tradition is transmitted exclusively from parent to offspring. In other cases selection will be overwhelmed by cultural factors, such as when a maladaptive tradition evolves rapidly by horizontal transmission. From this perspective it makes no sense to describe a tradition as being culturally selected. This notion conflates the factors that influence the rate and direction of inheritance with the process of differential reproduction. However, many theorists prefer to view cultural selection as a separate, analogous process to natural selection. William Durham (1990) offers one of clearest statements of this perspective. He begins by distinguishing two general “forces” that impact cultural evolution. Non-conveyance forces introduce cultural variation into a population. Included in this list are innovation, diffusion, migration and chance effects.  Conveyance forces affect the direction and rate of cultural evolution. Of these latter forces Durham identifies three different types which supposedly vary in strength. The first type of conveyance force is what Durham calls “transmission.” He offers no general description of this process, providing instead just a single example: all things being equal, the rate at which a tradition spreads through a population increases as its frequency increases. It is not entirely clear why this process qualifies as a form of transmission as opposed to the cultural analogue of what is known in biology as frequency-dependent selection. Nor is it obvious what else would qualify a transmission force for Durham. For instance, Cavalli-Sforza notes that in societies where children have little exposure to non-family members during the sensitive period when certain skills and values are acquired, the amount of horizontal transmission is minimized and culture evolves relatively slowly. We are left wondering whether such social influences qualify as transmission forces or, alternatively, as a form of cultural selection on Durham’s view. The second kind of conveyance force is natural selection, or, the dissemination of a tradition by the differential reproduction of its bearers. Durham views both transmission and natural selection as having only minor influences on cultural evolution. The third and supposedly most powerful conveyance force according to Durham is cultural selection. Included in this category are the decision rules and values that affect individuals’ choices between alternative cultural traditions. Durham notes that these values can be either “primary,” arising from genetically encoded preferences, or “secondary,” themselves inherited by cultural transmission. He assumes that most of the decision rules and values that exert a selective force on culture will be of the secondary variety –that is, they are themselves culturally inherited  traditions—but Durham admits that this is little more than a hunch.    This is not the place for a detailed analysis of the distinction between cultural transmission and cultural selection. It is noteworthy that one of the primary externalist objections to Darwinian theories of culture states that this distinction cannot be drawn. Critics like Fracchia and Lewontin (1999) argue that the analogy between cultural and natural selection is deeply misleading: since cultural traits do not undergo blind variation and selection they do undergo selection in the strict Darwinian sense. Whether the idea of cultural selection can be made tenable remains a hotly debated question that will reemerge in our discussion of memetics (Chapter 3). In the mean time, it remains an interesting question whether it is possible to develop an evolutionary theory of culture without endorsing the principle of cultural selection. The tradition that comes the closest to such an approach is the phylogenetic approach, which will now be discussed in some detail. (Back to Sections Menu)

5: Dual inheritance theory and niche construction. Dual inheritance theory has been aptly described as “a hybrid cross between memetics and evolutionary psychology, with a little mathematical rigour thrown into the pot” (Laland and Brown, 2002, p. 242). Like memetics, this theory views culture as a system of ideational phenomena (beliefs, skills, norms, etc) that can be transmitted in relatively discrete chunks among unrelated individuals. Like evolutionary psychologists, dual inheritance theorists assume that genetically encoded psychological dispositions influence the direction of cultural change. However, dual inheritance theorists offer a much more dynamic picture of the ways that genes and culture interact compared to either of these alternative frameworks. A typical dual inheritance model explicitly identifies two or more versions of a gene (A and a) as well as two or more cultural variants (C and c) that are distributed at a certain frequency in the population (e.g. AC: Ac: aC: ac).  Each gene/culture combination is assigned a fitness value that influences its frequency in the next generation (e.g. Ac > AC = aC < ac). In addition, cultural variants can spread horizontally among members of the same population (for example a certain proportion of AC changes to Ac). Once the relevant parameters are set, the model is run over many generations. Such simulations enable researchers to identify the ways that different genetic and cultural traits potentially coevolve. In one famous example, Feldman and Cavalli-Sforza (1989) developed a dual inheritance model to determine whether dairy farming could have coevolved with the gene for lactase production. In this model the gene for lactase experiences a fitness boost when paired with the cultural tradition of dairy farming, otherwise it is not selectively favored. Similarly, the tradition of dairy farming is most advantageous when paired with the gene that allows for the efficient absorption of lactose. This model reveals some unexpected results. The lactose/dairy complex does become rapidly established in the population, but only when dairy farming is highly heritable among related kin. This result is surprising in the sense that it would have been difficult to predict without a dynamic model that explicitly represents gene-culture interactions (Durham, 1991). The lactose example is somewhat unusual however in that, to date, dual inheritance models are not usually so empirically grounded. Rarely do these models identify known genes. More often the “genes” identified by dual inheritance theorists are actually traits with a complicated genetic basis that potentially interact with cultural factors in a multitude of ways. So, dual inheritance models are highly idealized. However, their simplicity is both a virtue and a vice. As Boyd and Richerson explain, “The goal of such models is to isolate the population level consequences of a limited set of processes by stripping away all the confusing detail due to other processes” (1987, p. 67). By exploring the properties of an idealized model it is possible to identify the minimal conditions required for certain traits or traditions to evolve. Idealized models also allow for the identification of general evolutionary trends that would be less visible in a collection of more complicated (though more realistic) models. However, as we shall consider momentarily, the simplicity of these models can also make their application to real-world situations questionable. Presentations of dual inheritance models tend to be fairly mathematically laborious and do not always make for engaging reading. However, Boyd and Richerson’s model of the evolution of ethnic markers (1987) is an exception to this trend. Ethnic markers are behaviours that signal an individual’s affiliation with a particular cultural group. Often these behaviours are arbitrary, like the lilt in one’s speech or a particular form of dress. Although they are found in every known culture, ethnic markers serve no obvious function and thereby pose something of an evolutionary puzzle. Boyd and Richerson’s model offers an interesting “how possibly” explanation for the evolution of ethnic markers. In their model, they imagine a population of individuals who must select a particular subsistence strategy (farming or herding) by observing how well each strategy is panning out for others. The environment is variable, so that in some generations herders do better than farmers and in other generations the opposite is true. The adaptive problem faced by each generation is which strategy is currently the best one going. However, as Boyd and Richerson note, in reality it is not always reliable to simply adopt whichever strategy seems to be working for one’s neighbors. Sometimes there are unknown interaction effects between the behaviour of interest and other practices that one adopts. For example, in some environments it is likely that becoming a successful herder requires cultivating a hair-trigger propensity for violence, a disposition that wards off potential cattle rustlers (Nisbet and Cohen, 1996). When such interaction effects are present it is not good enough to simply adopt the strategy that is most successful.  One must also adopt the strategy that is benefiting others whom one most closely resembles. Ethnic markers conceivably provide an index of the degree of cultural similarity between oneself and a potential demonstrator. So, by copying individuals who both share the same markers and are at the same time relatively successful one maximizes his or her fitness. An interesting feature of this model is that ethic markers tend to become more pronounced over time. This suggests that ethnic markers, though in one sense arbitrary, have an important adaptive function in allowing a population to adaptively track fitness peaks in a changing environment.    Through the use of such minimalist models, dual inheritance theorists have identified several important generalizations about the nature of gene-culture coevolution. For instance, Cavalli-Sforza and Feldman (1981) demonstrate how different types of horizontal transmission (many-to-one or one-to-many) can have a dramatic impact on the rate at which cultural traditions evolve. Another important result identified by Boyd and Richerson (1982, 1985) is that certain forms of intra-group horizontal transmission allow for group-level selection. Although lacking in empirical support, these models provide vivid depictions of the ways genes and culture can (and cannot) coevolve. An important criticism of dual inheritance models is that they sometimes make questionable assumptions about human psychology (Atran, 2001; Sterelny, 2006). Take Boyd and Richerson’s assumption that humans sample widely from the pool of available demonstrators, mimicking those who are both similar and successful. How realistic is this picture? One might argue that people rarely get the opportunity to sample from a range of cultural parents as opposed to having particular traditions foisted upon them. For that matter, the choice about which subsistence strategy to adopt is rarely such a simple two-factor decision. One of the potential dangers of using such idealized models is that the evolutionary impact of more complex (and arguably more realistic) decision rules are left unexplored.   A related criticism of dual inheritance models draws on the diffusion problem raised by Atran (2001) in his objection to meme theory. Recall that this criticism states that since the fidelity of a given tradition degrades as a result of social learning there is no stable cultural entity capable of undergoing cumulative evolution. Dual inheritance models typically help themselves to the assumption that cultural variants are, in fact, transmitted with high fidelity. This is another, potentially even more troubling respect in which these models are psychologically unrealistic. The diffusion problem, if it is real, threatens dual inheritance models just as much as it does memetics.   In response to this worry, Henrich and Boyd (2002) develop a model that aims to show how cumulative evolution can occur at the population level despite low fidelity transmission among individual demonstrators and learners. In their model they imagine that individuals are endowed with a “conformist bias” that encourages them to adopt the behaviour that is most prevalent in the community. Even when social learning is highly error prone, they demonstrate, this conformist bias operating in conjunction with strong individual-level selection allows the tradition to persist in a population. A similar result can be obtained by relaxing the degree of selection pressure and introducing a second “prestige bias” that leads individuals to copy the most successful individuals in the group. Again, even at low levels of fidelity, conformist and prestige biases compensate for the diffusion problem and allow for cumulative cultural evolution at the population level.  Sterelny objects to this response to the diffusion problem on the grounds that Henrich and Boyd’s model is psychologically unrealistic. In particular, Sterelny questions whether it is typically possible to estimate the long run success of a demonstrator by observing his or her behaviour (a challenge directed primarily at the prestige bias). Many traditions are relatively opaque, Sterelny notes, in the sense that they do not wear their reproductive consequences on their sleeves. This is especially the case for traditions that have delayed developmental consequences, such as the influence of certain parenting strategies on offspring’s moral and emotional development (Linquist, 2007). This view about the failure of dual inheritance models to explain cumulative evolutionary change raises a paradox similar to the one encountered in the case of memetics. On the one hand, we know that cumulative cultural evolution does occur. On the other hand, models of this process require unrealistic assumptions about the nature of human psychology and/or the strength of selection. Sterelny, for one, is unwilling to accept the evolutionary psychologist’s solution to this problem. That is, he doesn’t think that there are innately specified modules that compensate for the loss of information by social transmission. Instead, Sterelny suggests that humans have evolved a cultural solution of “scaffolding” the transmission of cultural materials. Practices like the explicit teaching of hunting and tool making or the telling of stories and fables effectively reinforce certain traditions in the minds of social learners, thereby compensating for the potential loss of information by transmission error. From an evolutionary perspective, Sterelny views social scaffolding practices as special case of niche-construction, a process whereby groups of organisms modify features of their environment in ways that benefit them as a collective. Niche construction theory is the fourth and final member in the family of recent approaches to cultural evolution being explored in this volume. This approach is sometimes described as turning the standard model of adaptation on its head. According to the standard model, the environment is regarded as a sort of filter that selects among organism-produced variation. When the environment changes new variants are selected, and so the process goes. Niche construction theory suggests an alternative way of coping with environmental change. Instead of adapting to environmental pressures, some populations modify their environments in ways that make certain adaptive changes unnecessary. Prototypical examples of niche construction often draw upon non-human examples of epigenetically inherited traits, such as the large mound-dwellings that termites create to protect the colony against temperature fluctuations. Each generation of termites expands upon its mound-dwelling and then passes the modified product on to future generations. Through this process of cumulative niche construction, successive generations of termites are able to build up a highly adaptive structure that relieves them from certain selection pressures. Of course, the adoption of a mound-dwelling lifestyle is bound to come with its own set of adaptive challenges. However, in some cases the fitness landscape created by a modified environment is easier for a population to climb than one that has not been altered. Adapting to fluctuating desert temperatures would arguably involve more radical physical and behavioural changes than the ones required for mound construction and habitation. Niche construction theorists see a direct parallel between these sorts of examples and what humans do when they construct certain social institutions. In some cases a social institution will take on an evolutionary momentum of its own, imposing selection pressure on both genes and other culturally transmitted traditions. This process is particularly salient in cases where a social institution is perpetuated by the community as a whole. For example, a system of legal or moral norms perpetuated by an entire community can serve as a background against which particular gene-culture combinations are more or less successful. In such cases selection potentially acts at three levels. First, there is potentially variation and selection at the level of the entire community or social group, for example, if some legal and moral norms make the collective more competitive than its rivals. Second, there is potentially variation and selection among cultural traditions within the community in their tendency to be more or less successful under the prevailing legal or moral system. Finally, both the community-wide social system and the individually varying cultural traditions potentially impose selection pressure on particular genes. A characteristic of niche construction theories is that they allow for variation and selection at these three levels.  In their defense of this perspective, Kevin-Laland, John Odling-Smee and Marcus Feldman (2000) argue that niche construction theory is an essential complement to dual inheritance models. In one of their more illustrative examples, these authors describe the case of the Kwa speaking yam cultivators of West Africa whose rainforest clearings led to the creation of breeding pools for mosquitoes. This environmental modification led to an increase in malaria and, in turn, selection for the sickle-cell allele that enhances malaria resistance. These authors argue that, “the causal chain is so long that simply plotting the cultural trait of yam cultivation against the frequency of the sickle-cell allele would be insufficient to yield a clear relationship between the cultural trait and allele frequencies” (Laland et al, 2000, p. 137). In this case it is necessary to identify three distinct systems that are capable of varying independently of one another: the cultural tradition of yam cultivation, the external environment in which mosquito pools form, and the alleles for sickle-cell anemia. As in the termite example, a modified feature of the physical landscape both enables the Kwa to adapt to their broader environment and at the same time serves as a selective niche to which they must genetically adapt.  Up to this point it has been argued that dual inheritance theory offers several advantages over alternative theories of cultural evolution. Unlike memetics, dual inheritance models explicitly represent the coevolutionary dynamics between particular traditions and alleles. Another advantage of dual inheritance models is that they abstract away from the details of particular evolutionary scenarios and strive for a general account of how certain types of traditions evolve. We have seen that in order to explain cumulative cultural evolution these simple models rely on some questionable psychological assumptions. Niche construction theory potentially provides a more detailed framework for understanding how cultural transmission works. Instead of being a “leaky” or error-prone learning process, cultural transmission potentially involves the active “scaffolding” of traditions in naïve social learners. This suggestion differs markedly from the alternative, evolutionary psychological hypothesis that genetically specified modules explain the fidelity of cultural representations. To decide between these alternatives the natural place to look is the psychological evidence. The emergence of dual inheritance models have sparked renewed interest in the mechanisms involved in social learning and transmission. It is to this subject that we now turn. (Back to Sections Menu)

 

 

7: Culture in nonhuman animals.  Until recently, the suggestion that culture might be found in other species would have been scoffed at by most scientists. Culture has historically been regarded as one of those sacrosanct traits like tool use (Allen, 1997), language (Deacon, 1997), and moral reasoning (Joyce, 2006) that distinguishes humans from other animals. This view was challenged in the 1960s by Jane Goodall and fellow primatologists who reported field observations of population-specific behaviours that appeared to be socially acquired (Goodall, 1968, 1973). Another example, potato washing in Japanese macaques, has become one of the most glorified cases of primate culture (our own species not withstanding). Primatologists were present when Imo, a young female macaque, first hit upon this strategy of removing soil from her food and they carefully documented the spread of this behaviour to her fellow troop members. In reporting this event, Masao Kawai (1965) was careful to describe potato washing as a precultural behaviour. However this and other animal traditions are now commonly described as instances of animal culture, full stop. This choice of wording would be less controversial if “culture” had an accepted theoretical definition against which such claims could be evaluated. But as many of the articles in this volume note, there is little agreement about what the defining features of culture are. The debate over how to label animal traditions is therefore more than just a semantic one. At issue is the question of whether human and animal cultures, though obviously different in certain respects, can be explained in terms of the same Darwinian principles. Theorists who view animal traditions as continuous with human culture tend to emphasize their similarities: both are acquired by observational learning, both can involve arbitrary or non-functional behaviours, both forms of culture are capable of descent with modification and local adaptation. However, critics who argue for a difference in kind note that animal traditions are fairly piecemeal in character, usually involving a patchwork of context-specific behaviours like nut cracking and termite fishing rather than an integrated suite of practices. A second difference is that (arguably) only human cultural representations are symbolic (Deacon, 1997), which seems an important factor in explaining their spread and development. Another critical difference is that human cultures have elements which are explicitly taught while, as far as anyone knows, all animal traditions are gleaned exclusively by observation (Sapolski, 2006). This fact has been used to explain another distinguishing feature: even the simplest forms of human culture are much richer than any animal tradition. Regardless of whether one is talking about tool making in ravens, song evolution in finches, or termite fishing in chimps, the potential for complexity and cumulative evolution appears quite limited. So there must be something distinctive about the human mind that explains the informational complexity of human culture. The four articles appearing in section 7 address these and other related issues. Robert Sapolsky (2006) challenges one of the purported differences between human and animal cultures, arguing that in some species culture is not as piecemeal as most researchers assume. Sapolsky acknowledges that many reported cases of animal culture involve isolated behaviours that occur in circumscribed contexts. However, he goes on to identify a less frequently described form of “social culture” that affects a broad range of different social interactions. The best documented example of social culture involves a particular troop of baboons that experienced a sudden loss of adult males due to disease. This event caused a sea change in the troop’s social milieu. Interactions went from being highly aggressive and stressful to relaxed and welcoming. The key feature of this example is that the adoption of a relaxed cultural style permeated a range of different behaviours including grooming rates, number of aggressive encounters, and individuals’ willingness to accept new troop members. Not only does this example challenge the assumption that animal culture is piecemeal, it also suggests that animal social cognition is more flexible than many authors have assumed. On the traditional view animal social cognition is regarded as highly domain specific. For example, the way that an animal responds to a dominance threat is thought to be unrelated to its parenting style or grooming behaviour. Likewise, humans are sometimes considered unique in their capacity for cross-domain reasoning (Sterelny, 2004). However, if Sapolsky is correct about the nature of social culture in baboons, these organisms are cognitively more flexible than it has been traditionally assumed.  Like the potato washing example, Sapolsky’s observations of social culture in baboons involved careful fieldwork spanning several years. Students of animal culture do not always have the time and resources for this kind of detailed analysis. Thus, in recent years there has been an effort to develop more efficient strategies for documenting animal culture. One of the most influential techniques was pioneered by Andrew Whiten and his colleagues (1999) who claim to identify a range of cultural differences among chimpanzee populations. These researchers drew upon existing behavioural reports from seven distinct field locations. Their analysis revealed 42 categories of behaviour that varied among the different research sites. In the next stage of their analysis Whiten et al excluded any behaviour that could be explained as an adaptation to the local environment. Once these ecologically meaningful behaviours are discounted, 39 behavioural differences remained. The majority of these differences involve foraging or feeding. For example, some chimpanzee use stones to pound nuts, others do not use any form of anvil but instead employ a stick to probe ant mounds, and so on. Whiten et al argue that these behaviours cannot be attributed to genetic differences among the populations. Nor, they argue, are these behaviours likely to have been acquired by individual (non-social) learning. On these grounds Whiten et al infer that chimpanzee groups possess at least 39 distinct cultural traditions. This study has inspired several similar investigations that have identified cultural traditions in monkeys, orangutans, whales and dolphins (Laland and Janik, 2006).  In each case the same methodology is employed: any population specific behaviours that are not ecologically meaningful and which cannot be attributed to genetic differences are identified as cultural. However, Kevin Laland and Vincent Janik identify several flaws in this methodology. These studies do not carefully explore the role that genetic differences might play in contributing to behavioural differences. Nor are the researchers who conduct these studies sufficiently familiar with local ecological conditions to rule out adaptation as an alternative explanation. More fundamentally, however, Laland and Janik object that this methodology rests on a pair of faulty assumptions. First, it is assumed that a trait is cultural only if it is not ecologically meaningful. The problem is that cultural traits can themselves evolve by natural selection and thereby promote ecologically meaningful behaviour. Second, Whiten et al’s methodology fallaciously assumes that behaviours are either culturally or genetically specified. In fact, no “cultural” trait lacks a genetic basis; and many “genetic” traits are modified by culture. Dual Inheritance theory offers a particularly vivid illustration of how both cultural and genetic factors contribute to the development of certain behaviours (see Section 5). As a way of transcending these problematic assumptions, Laland and Janik offer several alternative methods for identifying culture in animals.  In their article, “How do apes ape?” (2004) Andrew Whiten and his colleagues explore the psychological dimension of chimpanzee culture. The verb, “to ape” was introduced into the animal culture literature by Michael Tomasello (1996) as something of a technical term. Tomasello defined “aping” as a kind of imitation learning where the observer adopts a specific action from a demonstrator. Learning to fish for termites with a stick is not necessarily aping, on this view, unless the observer adopts the exact sequence of bodily movements from the demonstrator. Tomasello argued that according to the evidence that was available at the time, apes cannot ape. Instead, apes were thought to be capable of mere “emulation learning”, a form of stimulus enhancement where the observer learns something about the environment (e.g. that sticks can be used as tools) without acquiring a specific skill. However, as Whiten et al note, a considerable amount of research on ape’s capacity for social learning has transpired since the publication of Tomasello’s article. It is now recognized that apes can ape, the question is “how?”, or, more specifically, what learning strategies do apes employ when learning by observation?  Based on their review of the recent evidence, Whiten et al conclude that the distinction between imitation learning (or aping) and emulation learning is too course grained. Apes are capable of a variety of different forms of observational learning that fall between these two extremes. For instance, chimps are capable of “goal emulation” where they acquire the objective of a demonstrator (e.g. to acquire food from inside a container) without mimicking exactly the demonstrator’s movements. Whiten et al distinguish goal emulation from the less cognitively sophisticated task of “results emulation”, where the observer learns about a certain result from a demonstrator (e.g. that some containers hold food) without recognizing that the observer was striving to achieve some goal (e.g. looking for food). Apes also engage in “object movement reenactment” which involves copying the form of a caused object movement (e.g. swinging a hammer), though not necessarily by adopting the exact same movements as the demonstrator.  Generally speaking, Whiten et al note that apes tend to be more focused on the objects that a demonstrator is manipulating, and the results of those manipulations, than they are on the exact behaviours or strategies demonstrators employ.  If an observer acquires a goal from a demonstrator, but is unsuccessful in using his or her own strategy for achieving that goal, then the demonstrator might refocus attention on the way in which the demonstrator executed that end. This would be a case of frustrated goal emulation leading to full blown aping. However, as Whiten et al note, apes will resort to strict imitation only when their own attempts to achieve some goal have been unsuccessful. So, apes employ a collection of social learning strategies. Sometimes they learn that a particular object has the potential to be useful (e.g. as a general purpose hammer) without associating that object with a specific goal. At other times an ape will acquire a goal from a demonstrator, but insist on employing its own strategy for realizing that end. If, however, that strategy isn’t working an observer will sometimes consult the demonstrators exact movements and try to ape his or her actions exactly. There is some evidence that humans are less flexible in their social learning strategies. More often, a child will adopt the exact actions of a demonstrator (they will ape) without first striking out on their own. A simple way of viewing the differences is that children are more intent, at least initially, on copying what the demonstrator is doing than they are on deciphering the reason for doing it. It seems likely that this emphasis on behavioural process is a key ingredient in explaining the richness of human culture. However, the finding that chimpanzees are capable of imitative learning (aping) poses a puzzle for theories of cultural evolution. If chimps are capable of aping, then why is chimpanzee culture significantly less complex than human culture? The traditional explanation (Tomasello, 1993) appealed to chimps’ inability to ape as the reason for why useful behaviours, when they arise, are usually not preserved over successive generations. However, Whiten et al’s analysis suggests that chimp culture should be more complex than it is. Suppose that some chimp has hit upon a particular strategy for building shelters that requires following a particular sequence of steps. Others might initially attempt to construct this shelter using a strategy of their own. But after several unsuccessful attempts, one would expect those observers to consult the demonstrator a second time, paying closer attention to her techniques. Thus, one might expect to find at least some complex cultural artifacts – shelters, perhaps weaponry- given that apes have the capacity to ape (albeit a somewhat reluctant one). Tomasello (2001) identifies several additional features of the human psyche, besides the capacity for imitation, that potentially explain why human culture is so distinctive. One of these is our capacity for language. As evolutionary biologists John Maynard-Smith and Eors Szathmary (1997) have suggested, the emergence of language might have constituted a “major transition” in human evolution because it provides an efficient means for encoding vast amounts of information . Perhaps there is simply an upper limit to how cognitively complex a non-linguistic culture can become. However, this cannot be the whole explanation for why human culture is so different from what we find in other primates. Firstly, it is implausible that any tool more complex than a stick or anvil requires language to facilitate its social transmission. Even without language, chip culture could become a lot more complex than it is. Secondly, this explanation merely pushes the question back a level. If language is the necessary ingredient for complex culture, then what sorts of psychological abilities had to be in place before it could evolve?  Tomasello also mentions our capacity for joint attention as a key ingredient for human culture. From a very early age, an infant’s attention is drawn to the objects that she sees her caregivers attending to. Thus, from the beginning a child’s environment is interpreted through the eyes of her caregiver. Tomasello sees this capacity as being closely related to humans’ tendency to identify others’ as intentional agents (agents with beliefs and goals). So, perhaps it is our ability to read the intentions of others, to see that they have beliefs and goals, that explains our absorbency as cultural sponges. But this can’t be the whole story, either. Chimps are also capable of joint attention, especially at a young age. And as Whiten et al note, chimps seem quite adept at identifying and emulating the goals of their fellow troop members. Perhaps, then, the reason why humans are so culturally distinct lies not in a difference in kind but rather in a difference in degree. Like chimps, humans are capable of imitation. However we imitate more readily and are less likely to try a new strategy when we’ve seen one that works. Also like chimps, humans are capable of joint attention and of reading others’ intentions. However, in humans these capacities are exaggerated to the level of an obsession. As infants we are fixated on what our caregivers are attending to. As adults, we continue to interpret the world in terms of beliefs and desires even when none exist. Hence, the rudiments for complex culture appear to be present in other species, only in humans they are exaggerated. If this view is correct, one can imagine that it would be fairly easy to transform chimpanzees into a robustly cultural species. Only a few slight modifications would be required. Just turn up their interest in the thoughts and aims of others, have them engage in joint attention from an early age, and make them more conformist in their imitative proclivities. After a few thousand generations of cultural evolution these primates will potentially have evolved a complex culture rivaling what one finds in humans. (Back to Sections Menu)