Which of the following is not one of the types of selection focused on evolutionary theorists?

Summary

Human behavioral ecology is a young and explicitly Darwinian approach to the study of human behavioral variation. It redresses an absence of evolutionary considerations in the analysis of human behavior and social organization in the social and behavioral sciences. Since its inception in the late 1970s it has spawned the development of new journals and academic specialties explicitly devoted to training students to query the evolutionary bases of behavior. Its penetration into academic life has been uneven. It is most prominent in those disciplines such as anthropology and psychology where human evolution is considered relevant for a holistic understanding of human behavior or in economics where self-interest, methodological individualism, and maximization are key elements in modeling behavior. It has been resisted in disciplines such as sociology and political science where findings on human evolution are either ignored or, at best, regarded as irrelevant.

Behavioral Ecology

Human behavioral ecology (HBE) is the second of the principal contemporary approaches to applying evolutionary theory in archaeology. Archaeologists working in this tradition assume that people (and other animals) have evolved to strive for success in, and make reasonably intelligent decisions about, matters such as maximizing rate of food intake, defense of resources, and so forth, to the extent that these are connected with Darwinian fitness. They use tools derived in zoology and evolutionary ecology, which were in turn strongly influenced by approaches in economics, to examine the extent to which predictions based on these assumptions are borne out in the archaeological record. Decision making is usually assumed to be based on rational choice among alternative models, in conjunction with individual learning and innovation, and in the context of limited and costly information and various constraints in possible courses of action. HBE is related to sociobiology, though that field takes a more direct interest in reproductive success through its use of kin selection and other models that measure Darwinian fitness directly, rather than analyzing nonreproductive behaviors presumed to be related to fitness.

Behavioral ecologists explain behavioral variability through time, or within a population at a given point in time, by reference to relevant aspects of environmental variability (broadly defined to include the social environment). Traditional problems include explaining change in group size, sharing/exchange, land tenure/resource defense, prey choice/diet breadth, and settlement pattern. Although these problem domains may on first glance seem narrow, they are certainly broad enough to allow researchers in this tradition to study some of the most important transitions in human history – for example, the transition from foraging to agriculture and animal domestication. Recent HBE models, moreover, increasingly grapple with more social and even symbolic phenomena. One such development is the use of signaling theory, which suggests that self-interested individuals can be expected to engage in individually costly but frequently group-beneficial signaling behaviors, with such behaviors becoming more socially conspicuous in proportion to an individual's ability to produce them. Rebecca Bliege Bird and Eric Alden Smith suggest that costly (honest) signaling explains puzzles including unconditional generosity (for example, in feasting), pursuit of risky big game for public consumption, ostentatious commitment to religion, artistic skill, monumental architecture, and so on.

Human Behavioral Ecology

Evolutionary psychology may be the best known of the three approaches that we consider here, but human behavioral ecology is another perspective that emerged around the same time (if not earlier) and is also firmly rooted in the neo-Darwinian synthesis in its attempt to provide evolutionary explanations for human behavior (Laland & Brown, 2011). Human behavioral ecologists typically employ the same toolbox of methods, concepts, and models that are employed by behavioral ecologists studying other species (Nettle et al., 2013a). They have therefore developed an extensive program of research using mathematical models to test whether the foraging behavior of hunter-gatherers conforms to the prediction of optimal foraging theory, in a similar fashion to results from research on nonhuman animals (Kelly, 2013; Winterhalder & Smith, 2000). A key focus of research by human behavioral ecologists relates to the extraordinary flexibility and diversity of human behavior. For human behavioral ecologists, this reflects the fact that humans have the capacity to adaptively adjust their behavior to variable ecological circumstances in a way that will maximize reproductive success (Smith, Mulder, & Hill, 2001). As summarized by Nettle et al. (2013a, p. 1032): “Selection favors various mechanisms for plasticity, such as individual and social learning, exactly because they allow individuals to acquire locally adaptive behavioral strategies over a range of environments.”

There is now an extensive body of research that has been carried out within the human behavioral ecology approach on a diverse range of topics including foraging, mate choice, parental investment, sexual division of labor, cooperation, and social structure (see Nettle et al., 2013a; Winterhalder & Smith, 2000 for reviews). Nettle et al. 2013a argue that the human behavioral ecology approach possesses a number of key strengths including broad scope, methodological rigor, ecological validity, and vitality.

Evolutionary psychology and human behavioral ecology share a number of fundamental assumptions. Perhaps most importantly, adherents to both approaches recognize the fundamental importance of using evolutionary theory (in its neo-Darwinian guise) to advance our understanding of human behavior. There are a number of differences between these two approaches, however, although these have perhaps been somewhat exaggerated. The most straightforward difference reflects different institutional backgrounds: evolutionary psychologists are largely trained as psychologists, and human behavioral ecologists typically have academic training in anthropology. This difference often manifests itself in the use of different research methods with different populations: human behavioral ecologists are more likely to focus on hunter-gatherer populations or small-scale human societies using ethnographic research; evolutionary psychologists typically study modern Western populations using standard psychological research methods (although as the analysis of Nettle et al., 2013a suggests, these differences are in no way absolute). In addition to these institutional and methodological differences, there are also a number of more substantive points of difference.

One prominent difference concerns the proposed structure of the human mind. As we have seen, evolutionary psychologists are largely committed to the idea that the mind is composed of a large number of domain-specific psychological mechanisms that have evolved to solve specific adaptive problems. Human behavioral ecologists, by contrast, typically view the human mind/brain in more domain-general terms—rather than a bundle of specialized mechanisms and processes, the human mind has evolved to respond adaptively to a wide range of different ecological contexts. In part this difference reflects a different emphasis on what needs to be explained: evolutionary psychologists argue that psychological mechanisms are the main unit of analysis, whereas human behavioral ecologists focus more on behavior. This leads evolutionary psychologists to a focus on universal characteristics that collectively reflect our human nature, whereas human behavioral ecologists see behavioral flexibility and diversity as the key characteristic of our species.

A second issue concerns the favored approach to studying psychological and behavioral adaptations. Because human behavioral ecologists stress the flexible nature of human behavior and our capacity to adjust behavior to reflect local ecological contexts, they argue that it is appropriate to measure current reproductive fitness as a means to test hypotheses about the evolution of human behavioral characteristics (Mulder, 2007). Evolutionary psychologists, in contrast, emphasize the fact that contemporary environments are significantly different from the environments that we evolved in, and hence current reproductive success may be a relatively poor guide to identifying adaptations.

Despite some substantive differences between the evolutionary psychology and human behavioral ecology camps, there is a significant overlap between the two approaches. Moreover, as Brown et al. (2011) note, there have been a number of attempts to integrate—or at least reconcile—the two perspectives and in many respects they can be viewed as complementary approaches. Before we consider how this might be achieved, we need to consider the third major approach to applying evolutionary theory to human behavior: cultural evolutionary theory.

Changes in Focus

Three current major evolutionary approaches to human behavior are detailed below. All of these approaches can be understood in contrast with – in some cases as reactions to or developments of – sociobiology.

The first approach, human behavioral ecology, represents a shift in focus compared to sociobiology, away from seeking universals and on to understanding diversity. The second, evolutionary psychology, was a self-conscious break with sociobiology for at least some of its practitioners, and contrasts with that earlier approach insofar as it focuses not on behavior itself, but on the psychological mechanisms that underlie and generate behavior. Finally, the third approach detailed below, gene–culture coevolution, represents a move away from sociobiology's gene-centric and adaptationist viewpoint by attempting to integrate cultural with genetic influences on human behavioral evolution, and also by recognizing the potential for cultural forces to lead to maladaptive outcomes over evolutionary time.

2.1 Complexity and the Natuurwissenschaften: evolutionary dynamics

The examples we have just considered address two fundamental questions in anthropology: the role of symbols in social life, and the relationship between agency and social structure. Here we take up another venerable question on which contemporary anthropology is sharply divided: are Darwinian processes at work in the social or cultural realms? As before, we begin by defining the issues from the perspective of complexity theory; sketch the outlines of a relevant mathematical model, and briefly consider some empirical examples.

Darwinian models in anthropology generally assume that behaviors, like genes, are constantly being scrutinized by selection. Thus “analyses typically take the form of the following question: in what environmental circumstances are the costs and benefits of behavior X such that selection would favor its evolution?” [Smith and Winterhalder, 1992, 23]. To investigate selection at the level of individuals, we compare their fecundity. The “fittest” individuals are those that produce the most offspring. Because there is always variation in fecundity, at this level it would appear that selection is always at work. But one of the key insights in the mathematical analysis of complex systems is the concept of emergent properties. In this context, one can ask, what would be the population-level consequences of selection at the level of the individual? Figure 7 illustrates three alternatives. In the first case (Fig 7a), selection is not present so the make-up of the population as time goes forward depends on drift (about which more will be said below). If selection occurs (Fig. 7b) the effect at the population level is to reduce the diversity of the population. But the evolutionary consequences of selection depend on how long it persists. Fluctuating dominance, in which some individuals in each generation attain higher reproductive fitness, but do not pass this on to their descendants, produces Red Queen dynamics (Figure 7c). The Red Queen forestalls evolution by preventing any individual or group from gaining a lasting advantage. As she explained to Alice, sometimes “it takes all the running you can do to keep in the same place.”

What about the neutral case? Until the 1960s, biologists assumed that almost all mutations are under selection. But in 1963 geneticist Motoo Kimura asked what genetic variation would look like if selection were not present. Even in the absence of selection, Kimura reasoned, evolutionary change will occur as a result of chance, and this can be analyzed with tools from probability theory. As Kimura wrote in 1983, “It is easy to invent a selectionist explanation for almost any specific observation; proving it is another story. Such facile explanatory excesses can be avoided by being more quantitative” [Kimura, 1983].

The processes that lead to neutral equilibrium can be explained with the statistician's favorite example, a bag of colored marbles. To model the effects of drift, the experimenter reaches into the bag and grabs two marbles. One is randomly tossed aside and the other is magically duplicated; the latter (identical) pair of marbles is put back into the bag. Starting with a bag of ten marbles, each with a different color, all the marbles in the bag will be the same color after a few replacements. This process will take much longer with bags of 100 or 1000 marbles. Thus drift reduces the number of colors in the bag. Mimicking the effects of mutation can counteract this process: from time to time a marble with a new color is added to the bag as a replacement for a discarded marble. Neutral equilibrium is reached when the introduction of new colored marbles by mutation (or migration) matches the rate at which existing colors are removed by drift.

A charming example that demonstrates the application of the neutral theory to culture was recently published by Hahn and Bentley, who investigated the changing frequency of baby names in the United States. One can easily imagine selectionist explanations for the prevalence of names; for example, in each generation parents might preferentially choose the names of culturally dominant or prestigious individuals for their children. The alternative, neutral hypothesis, predicts a distribution of names governed solely by chance. While any number of selectionist models could be proposed for the frequency distribution of baby names, there is only one neutral distribution for any given dataset. This neutral distribution depends solely on the total population size and the rate at which new names appear.

In 2002, the Social Security Administration published the thousand most common baby names in each decade of the twentieth century, based on a sample of 5% of all social security cards issued to Americans. Most parents chose a pre-existing name for their infant, but occasionally a new name was introduced. Hahn and Bentley found that the distribution of names from one decade to the next fits a power-law distribution with an r2 value above 0.97. A very few names were extremely popular, while others persisted at decreasing frequencies. However, the prevalence of certain names also changed as the century progressed.

To explain this stable distribution of name frequencies despite changes in the popularity of particular names, the researchers created a simulation based on Kimura's neutral theory, and compared these results with the observed data. In a neutral model, random drift causes changes in the frequencies of names as they are repeatedly sampled; some are lost, other arise de novo, while still others drift up or down in frequency. To simulate this process, N new babies appear at each time-step and are named by copying the name of a randomly chosen baby from the previous time-step. A small fraction, m, of the N babies receive a name that was not present earlier. The neutral theory predicts that, at equilibrium, the number of variants (baby names) with frequency x at a single moment is given by θx-1(1-x)θ-1 where θ = 4Neμ [Slatkin, 1996]. A regression between the logs of the average values of the model and the data yielded r2 = 0.993 for boys' names and r2= 0.994 for girls' names. Power law distributions can result from many causes. In this case, the neutral theory predicts not only the power law distribution, but also its slope, with near-perfect accuracy. Chance, not selection, determines the frequencies at which baby names occur in the US population.

In genetics, the neutral theory was hotly debated for decades. As Kimura observed in his 1968 paper, the prevalent view in the 1960s held that almost all mutations are under selection, and this opinion was slow to change. But as Stephen J. Gould wrote in 1989, “These equations give us for the first time a baseline criterion for assessing any kind of genetic change. If neutralism holds, then actual outcomes will fit the equations. If selection predominates, then results will depart from predictions” [Gould, 1989]. This led to a fundamental reformulation of how selection was viewed in molecular biology: geneticists now infer selection only when it can be shown that the assumption of neutrality has been violated. As E.G. Leigh observed in a recent retrospective about the neutral theory, “no population geneticist, not even Kimura, sought to deny the importance of adaptive evolution. Instead, all major workers “were interested, at least to some degree, in how neutral processes affected adaptive evolution” [Leigh, 2007, p. 2076]. In ecology, as Leigh further noted [ibid, p. 2087], everyone, even the advocates of the neutral theory, recognize that neutral theory is wrong when taken to extremes: adaptive processes clearly do matter. In genetics, the question of precisely which regions of the genome are under selection is being revisited using neutral theory [Hey, 1999].

But in anthropology, Darwinian models of cultural evolution continue to focus on selective processes occurring at the level of the individual, rather than the population-level consequences [Richerson and Boyd, 2006]. Most research in human behavioral ecology is explicitly pan-selectionist, asking “what are the fitness effects of different strategies in particular environments?” [Clarke and Low, 2001] rather than “are the behaviors we observe actually under selection?” In “The Spandrels of San Marco and the Panglossian paradigm”, their well-known critique of pan-selectionism in biology, Gould and Lewontin commented on the need for an explicit test for ‘adaptationist’ explanations:

We would not object so strenuously to the adaptationist programme if its invocation, in any particular case, could lead in principle to its rejection for want of evidence. We might still view it as restrictive and object to its status as an argument of first choice. But if it could be dismissed after failing some explicit test, then alternatives would get their chance. [Gould and Lewontin, 1979]

The neutral theory provides such a test, for cultural evolution as well as genetics and ecology. It shifts the analytical focus from selection at the level of the individual, to the population-level consequences of both selection and neutral processes over the course of multiple generations. In place of the pan-selectionist assumptions of evolutionary game theory and behavioral ecology, it provides a mathematically explicit null model. For example, a recent study investigated the magnitude of selection effects stemming from reproductive competition among men in 41 Indonesian villages [Lansing et al., 2008]. Many studies have argued that reproductive skew biased toward dominant or high-ranking men is very common in human communities: “In more than one hundred well studied societies, clear formal reproductive rewards for men are associated with status: high-ranking men have the right to more wives” [Clarke and Low, 2001]. Demographic statistics collected over short time scales support these claims [Winterhalder and Smith, 2000]. Although variation in male fitness is known to occur, an important unanswered question is whether such differences are heritable and persist long enough to have evolutionary consequences at the population level.

In this study, genetic data showed that dominance effects generally do not persist over multiple generations. The lack of evidence of reproductive skew in these communities means that heritable traits or behaviors that are passed paternally, be they genetic or cultural, are unlikely to be under strong selection. The discovery that neutral processes can explain most haplotype frequency distributions in these communities parallels earlier results from the development of neutral theory in genetics and ecology. As Kimura observed in his original article, the prevalent opinion in the 1960s held that almost all mutations are under selection [Kimura, 1968]. This opinion was slow to change. More recently, ecologists similarly have suggested that a neutral model, in which species in the same trophic level are functionally equivalent or neutral with respect to each other, might adequately explain species-abundance distributions in ecological communities [Hubbell, 2001]. In anthropology, the recent availability of appropriately sampled community-level polymorphism data now enables us to distinguish both genetic and cultural selection from neutral demographic processes with surprising precision. In these Indonesian communities, male dominance seldom translates into increased fertility among descendents over evolutionary timescales.

In both genetics and ecology, the neutral theory played an important role in introducing a systems-level dynamical perspective to evolutionary theory. One advantage for anthropology as a relative latecomer to this perspective is that anthropologists are in a position to benefit from several decades of theoretical work, including a substantial body of elegant mathematics. A particularly salient lesson may be the identical outcome of the debates that occupied both genetics and ecology for years, both of which pitted pan-selection against pan-neutrality. In both fields, this debate was largely resolved by adopting a view of neutrality as a null model, rather than as a strict alternative to Darwinism [Alonso et al., 2006; Hu et al., 2006].

In the Context of Evolutionary Anthropology

Three broad approaches to the study of the evolution of human behavior can be distinguished by their assumptions (Laland and Brown, 2011). This section provides brief descriptions of each and shows how gene-culture coevolution fits in with these schemes. The descriptions will be stylized in their brevity, and it can be argued that new generations of researchers are drawing across these fields to address evolutionary questions appropriate for the context in which they work.

Perhaps, the most high-profile approach to study the evolution of human behavior has been evolutionary psychology, which puts an emphasis on the genetic evolution of psychological adaptations. Commonly, the assumption is made that behavior and expressed preferences, for instance, in mate choice, reflect psychology that was shaped by natural selection in ancestral environments. By contrast, human behavioral ecology enquiry is focused on the effects of contemporary ecological variation on adaptive behavior (see Human Behavioral Ecology). Here, two common assumptions are that human behavior is currently adaptive (maximizes inclusive fitness), and that according to the phenotypic gambit, the mechanism underpinning the behavior largely can be ignored. Thus, optimality is considered not to be constrained by mechanism but rather reflects an often-complex trade-off resulting from the interaction of marginal fitness benefits in a local ecology.

By distinction from these schools, gene-culture coevolution is principally consistent with the third approach, which is the field of cultural evolution (Cavalli-Sforza and Feldman, 1981; Boyd and Richerson, 1985; Mesoudi, 2011). This field focuses on the micro (within population) and macro (between population) patterns of spread of socially transmitted information, in the form of ideas, beliefs, behaviors, and material culture. The cultural evolution approach does not require the evolutionary psychologists' prior assumption of past adaptation or the behavioral ecologists' assumption of optimality. Instead, heritable traits are assumed to be subject to descent with modification, through some form of social transmission and innovation. The framework accounts for demic selection, considered equivalent to natural selection, by differential survival and reproduction, and cultural selection, which accounts for differential adoption and reversion from the use of a culturally acquired trait (Feldman, 2008). Other standard evolutionary features – such as drift, migration, and trait linkage – also can be considered as appropriate.

The modeling of cultural evolutionary or gene-culture coevolutionary dynamics is typically distinct from memetics in that there is no need to consider the socially transmitted trait as a replicator; however, there does need to be some effect of social learning, such that the probability that a learner acquires a trait is affected in some way by the behavior of another individual or its products (e.g., learning directly from material culture). One focus of cultural evolutionary theory is to consider the impact of individual-level learning mechanisms and cognitive biases on population-level patterns of cultural evolution.

In some regards, gene-culture coevolution can be seen to share common aspects with both evolutionary psychology and human behavioral ecology. Of interest to evolutionary psychology, gene-culture coevolution models have been used to examine the genetic evolution of predispositions for various biases in social learning cognition, including nonlinear frequency-dependent biases, such as conformity (to copy the majority) and payoff-related biases, such as copying successful individuals. Indeed, it is thought that the gene-culture coevolution of prestige bias can result in the cultural evolution of maladaptive behavior (Boyd and Richerson, 1985), a result consistent with evolutionary psychology and not human behavioral ecology. Consistent with human behavioral ecology, however, gene-culture coevolution commonly predicts the evolution of adaptive behavior in contemporary environments, where genetic variation continues to evolve in response to culturally derived selective environments (the cultural process of modifying the selective environment can be referred to as cultural niche construction; Kendal et al., 2011).

The gene-culture coevolutionary framework is also consistent with a relatively recent cross-disciplinary perspective on evolutionary theory interested in the role of so-called soft inheritance, or nongenetic inheritance, on the evolutionary processes. Nongenetic modes of inheritance have been carved up in a number of different ways. For instance, while Jablonka and Lamb (2005) have distinguished epigenetic, behavioral, and symbolic forms of inheritance, niche construction theorists have highlighted ecological inheritance of semantic information and resources, including forms of cultural inheritance (Odling-Smee et al., 2003).

Soft inheritance is considered important in genetic evolution as it accounts for genetic selective environments that are a function of the distribution of soft-inherited variants, which is not, itself, predicted by contemporary or ancestral genetic variation (if it were, then, a purely population genetic model would be most parsimonious). Thus, although it may be perfectly reasonable to distinguish the orthogonal questions of why a trait evolved and how it develops within an individual, the gene-culture coevolutionary perspective deals with cases in which the most parsimonious model for why a genetic trait evolved requires explicit accounting for the soft inheritance of acquired characteristics during development.

An Overview of the Book

This book is divided into three parts. In the first part, an overview of the evolutionary framework that we will be using in the remainder of the book is presented. We begin with a review of the key conceptual ideas in evolutionary biology that are important for understanding the application of evolutionary theory to human behavior. This material may be familiar to many readers, but given the relative lack of formal training in evolutionary biology for social scientists, we think this review is crucial to ensure that key processes and theories such as natural selection, sexual selection, parental investment theory, and life history theory are clearly articulated. We also pay particular attention to recent developments in evolutionary thinking that some scholars argue provide an “extended synthesis” that builds on and extends the core ideas of the modern synthesis in evolutionary biology. Of particular relevance for this book is the recognition that nongenetic mechanisms of inheritance—including culture—are essential in the understanding of evolutionary processes. In the second half of Chapter 2, we offer a brief overview of our current understanding of human evolution, from our split with the lineage that led to chimpanzees to the present. Criminologists often recognize the importance of historical processes in understanding patterns of crime and punishment; in this chapter we simply extend the time horizon of interest back several million years. Exploring the “deep history” of our species is important, because it offers the appropriate context for understanding the evolution of our uniquely human nature and thus provides a grounding for the—often implicit—assumptions about humans that sit within theories of crime and punishment (Agnew, 2011a).

In Chapters 3 and 4Chapter 3Chapter 4, these assumptions are brought to the fore. Chapter 3 reviews the various different approaches that have been employed to explain human behavior from an evolutionary perspective, focusing on evolutionary psychology, human behavioral ecology, and gene–culture coevolutionary processes (Durrant & Ward, 2011). We argue in this chapter that a pluralistic approach that draws from each of these three perspectives provides the most promising avenue for advancing our understanding of the evolutionary underpinnings of human behavior (including criminal behavior and our responses to crime). In Chapter 4, we develop and present a conceptual framework for integrating evolutionary explanations with mainstream criminological approaches to understanding crime and our responses to crime. Central to this framework is the recognition that explanations can be drawn from different levels of analysis, and that one of the key tasks is to successfully integrate theories in ways that improve our understanding of the phenomenon of interest. Tinbergen’s (1963) distinction between explanations that focus on evolutionary function, evolutionary history, development, and proximate processes provides an enduringly useful way of understanding how different types of explanation can be employed to understand any given behavioral phenomenon. With some qualification, and a particular role for social-structural and cultural explanations (which, we argue, can be viewed in both distal and proximate terms), we use this framework for organizing the theoretical approaches for understanding crime that are used in the second part of the book.

In part two of the book, we focus on theoretical approaches to explaining crime. We begin in Chapter 5 by focusing our attention specifically on the evolution of cooperation. We think that this topic is absolutely crucial for the subject matter of interest to criminologists, and, as Agnew (2011a) notes, almost all criminological theories have specific assumptions—not necessarily grounded in the relevant literature—regarding our “natural” tendencies to act in a selfish or cooperative manner. As we outline in the chapter, an extensive body of research clearly indicates that although selfishness and conflict will always be features of our behavior, we are in many respects “natural-born” cooperators. Each of the four following chapters in this part of the book focuses on one or more specific levels of analysis as we have outlined them in Chapter 4. Thus, in Chapter 6 we address distal explanations for crime by examining the evolutionary history and function of specific criminal behaviors. Our focus here is largely on violent crime (including sexual violence), but our general analysis has implications for other kinds of offending including drug use, property offending, and white-collar crime. In Chapter 7, we shift to considering the developmental origins of criminal behavior. A central task for any developmental theory of offending is to account for the dramatic increase in the prevalence of offending during adolescence and early adulthood, while also explaining why some offenders are much more likely to desist than others. We demonstrate that current developmental theories of crime, alongside our emerging understanding of normative developmental processes, can be enriched by recognizing both the evolutionary “function” of human-specific developmental trajectories and the way in which adaptive individual differences emerge in different social and environmental contexts. Chapter 8 addresses the proximate causes of crime. These are a somewhat mixed bag of processes including characteristics of individuals (e.g., cognitions), situations, and interpersonal social interactions. We also recognize here the importance of human agency and discuss how this can be reconciled with the evolutionary framework that we adopt in the first part of the book. The final chapter of Part II tackles cultural and social-structural explanations for crime. Although it may seem that evolutionary approaches have relatively little to offer in terms of understanding the cultural and structural processes that influence crime and that can account for differences in offending across time and place, we argue that the gene–culture coevolutionary approach outlined in Chapter 3 can help us to understand the emergence of specific cultural and social-structural contexts and why they influence crime (and our responses to crime) in specific ways.

In talking to friends and colleagues about the value of evolutionary approaches in criminology, many (but by no means all!) are willing to concede that we can improve our understanding of criminological phenomena by drawing from evolutionary theory; however, they remain skeptical about the practical usefulness of this knowledge. After all, if certain behaviors reflect specific evolutionary histories, how can we meaningfully intervene to change those behaviors? In the final part of the book, we respond to this concern by fleshing out the practical value of an evolutionary approach to improving the way that we respond to crime. We begin, in Chapter 10, by considering the evolutionary origins of the human motivation to punish offenders (norm violators) and what this means for the development of a criminal justice system that both resonates with our intuitive notions of justice, and responds to offending in a humane fashion. We argue that an evolutionary approach can help us to recognize that punishment is an essential feature of human societies, yet best serves its evolved function to the extent (in most cases) that it adopts an inclusive approach to the treatment of offenders. In this chapter, we also consider what an evolutionary approach has to contribute to our understanding of crime prevention. More specifically, we demonstrate how a clearer understanding about the causal origins of offending can help us to develop both social and situational crime prevention initiatives that are most likely to succeed in reducing crime. In Chapter 11, we discuss an evolutionary approach to understanding offender rehabilitation and reintegration (Ward & Durrant, 2011a, 2011b). Building on our understanding of human cooperation outlined in Chapter 5, and the need to recognize intrinsic human needs, we argue that a central task of offender rehabilitation and reintegration is to create the internal and external conditions that are most likely to foster altruistic behavior.

The first couple of decades of the twenty-first century are proving to be an exciting time for criminologists. Recent developments in our understanding of the biological underpinnings of crime offer to add to our already rich knowledge of the proximate psychological and situational factors that have been identified as playing key roles in offending. A now-extensive body of knowledge regarding the developmental trajectories of offending, and how these relate to normative developmental processes, has significantly improved our understanding of the factors that play a role in adolescent offending and contribute to desistance in adulthood. Ongoing theoretical and empirical work on macrolevel structures and processes continues to inform our understanding of patterns in offending, both within and across state and national borders. The time is ripe, we argue, to recognize the added value that evolutionary approaches can offer to our extant body of knowledge concerning crime and responses to crime. The topics that perennially engage criminologists are also of central concern to evolutionary behavioral scientists. To best advance our understanding of crime and to tackle the crime-related problems that subsequently emerge, therefore, we cannot afford to leave to one side the insights that evolutionary theory has to offer.

2.1 Human behavioral ecology

The approach known as human behavioral ecology employs much the same methods, concepts, and models utilized by behavioral ecologists who study the behavior of non-human animals from an evolutionary perspective. Human behavioral ecologists, for instance, have explored to what extent the foraging behavior of hunter-gatherer groups conforms to predictions made by optimal foraging theory, a theory widely employed in the study of non-human animals. A critical assumption of human behavioral ecology is that human behavior is extremely flexible and that, largely speaking, humans behave adaptively as they adjust their behavior to different social and ecological circumstances in a way that maximizes reproductive fitness (Smith, Borgerhoff Mulder, & Hill, 2001; Winterhalder & Smith, 2000). Human behavioral ecologists typically focus their attention on hunter-gatherer populations or on small-scale human societies using ethnographic research methods and have generated a significant amount of research over the last 35 years on topics such as foraging, mating strategies, and parental investment.

2.1 Evolutionary Social Science: a causal evolutionary model for explaining societal differences

Evolutionary Social Science (not abbreviated to avoid confusion with evolutionarily stable strategies) shares features with both human behavioral ecology and evolutionary psychology. The similarities and differences are outlined in Table 1, which is loosely based on Winterhalder and Smith (2000). The table highlights many differences in these related approaches. The key points are that behavioral ecology focuses on human adaptations to life in subsistence societies whereas Evolutionary Social Science focuses on modern societies. Evolutionary psychology focuses primarily on cross-societal universals that are interpreted in terms of pan-human adaptations, although most evolutionary psychologists recognize that psychological development proceeds differently in response to varied environments, such as varied levels of psychological stress during childhood (Belsky, Steinberg, & Draper 1991; Del Giudice, 2009), an approach that is often referred to as “life history theory”.

Table 1. Evolutionary Social Science compared to closely related fields.

Modern human social behavior can be causally linked to ecological pressures using four necessary key assumptions that form the core of Evolutionary Social Science (Barber, 2007, 2008). These assumptions are: (1) that modern societies owe their character to an interaction of hunter–gatherer adaptations with the modern environment (interactionism); (2) that some changes in societies are due to changes in individuals (methodological individualism); (3) that historical changes and cross-societal differences can be due to similar adaptational mechanisms (counter cultural relativism); (4) and that different social contexts modify individual development in adaptive ways (adaptive development). These four assumptions must be made if evolutionary explanations are to be applied to the problem of explaining societal differences in violent crime (or anything else). A corollary is that if any of these assumptions is wrong, evolutionary explanation for societal differences may be impossible.

Each of the above mechanisms is relevant to variation in violent crime. Interactionism means that human adaptations relevant to direct mating effort (which increases violent crime, Minkov, 2009) are influenced by novel economic factors, such as the relative independence of some working women from economic support by their sexual partners, particularly in the context of generous state provisions for child care, such as those in modern social democracies. If more individual women opt for sexual intercourse prior to marriage this increases the pool of women available for extramarital sex which, in turn affects the viability of direct mating effort by men as an alternative to marriage (methodological individualism). Such phenomena can account both for societal differences and for changes in crime rates over time (counter cultural relativism, Barber, 2003a).

Abusive parenting has been identified as a cause of antisocial behavior and crime (see below). Evolutionary Social Science reinterprets such phenomena through the prism of adaptive development. Does parental behavior facilitate the kind of reproductive strategy that is likely to succeed in a particular social context? For instance, children maturing in an urban slum might learn to be tough, suspicious, and street smart thereby protecting themselves from being taken advantage of by others. Specific parenting practices, such as corporal punishment, may promote this phenotype (Nightingale, 1993). This approach to adaptive development is within the mainstream of evolutionary psychology (Del Giudice, 2009).

Given this theoretical backdrop, variation in violent crime over generations, and among nation states, can be thought of as one manifestation of ancient adaptations for mating competition as they play out in varied modern environments. One aspect of differential expression of mechanisms for mating competition is adaptive development, the process through which the violent tendencies of young people are affected by their familial and community surroundings. With this theoretical framework in place, it is time to review evidence that violent crime varies predictably with marriage market conditions such that high levels of direct mating effort are correlated with high rates of violent crime.

2.2 Human behavioral ecology and niche construction

Emerging from common roots in natural history, ecological theory has always been closely linked to concepts of biological evolution. Evolutionary mechanisms are usually assumed responsible for the morphological and behavioral characteristics that provide relative fitness to the organisms and populations found in ecosystems at any given time. As such, ecosystems can be viewed as emergent (and evolving) properties of the evolutionary histories of their components — a temporal construct. Reciprocally, those evolutionary histories arise from the interactions of organisms in ecosystems — a spatial construct. Ecosystems condition the field of evolutionary possibilities for change at any given moment. Collectively this bivalent, time-space dynamic makes explaining ecological change uniquely challenging. How can we explain the evolution of system components (e.g., populations and ecological communities) and aggregate systems themselves? Evolutionary ecology was developed explicitly to study the intersection of ecology and evolutionary biology in order to take on the first of these questions: how to study the evolution of populations and adaptive design of organisms in terms of their changing ecological settings (Winterhalder and Smith, 1992). This biologically coherent paradigm explicitly set out to develop understandings of the ‘microfoundations’ of evolutionary history, and as such, could be an important ingredient in efforts to explain ecodynamic processes (see Winterhalder, 1994, for an argument for the centrality of evolutionary ecology in any ‘historical ecology’).

Behavioral ecology is the branch of evolutionary ecology studying ecologically adaptive (i.e., fitness enhancing) behavioral strategies (Krebs and Davies, 2009). Behavioral ecologists employ optimality models tuned to ecological parameters to derive deductive predictions about how behaviors should vary as environmental conditions change. Those predictions are compared with empirical observations, and the degree of coherence between predictions and observations help guide refinements in models and build or challenge confidence in starting assumptions. Human behavioral ecology (HBE) was born when a handful of anthropologists, and later archaeologists, started applying the behavioral ecology framework to understand patterned human behavior (Winterhalder and Smith, 1981, 1992, 2000). Initial approaches focused on simple economic optimization of foraging alternatives among small-scale, subsistence-based communities. Optimal foraging theory models, carried over from the study of non-human animals, dominated this early research (e.g., Winterhalder, 1981; Yesner, 1981). Over the last 40 years, HBE has helped develop a broad theoretical tool kit for understanding the ways people evaluate choices in food procurement, mobility, divisions of labor, task-group membership, social affiliation, prestige and social subordination (Boone, 1992; Kaplan and Hill, 1992; Kelly, 1995; Smith, 1981; see Nettle et al., 2013).

From its early foundations in optimal foraging, HBE theory has been integrated into more complex evolutionary models of socio-ecological systems and used to understand or predict constellations of human behavior in the past that may have driven system-level changes (e.g., Broughton, 1994; Butler, 2001; Fitzhugh, 2003; Kelly, 1995; Kennett, 2005). In these and similar applications, HBE has provided broad insights. Even so, the HBE approach sheds only limited light on the evolution of the social institutions and larger socio-ecosystems in which those behavioral strategies are enacted. Some HBE scholars have sought to overcome this deficiency through simulation modeling (e.g., Agent-Based Models) to evaluate the extent to which complex organization can emerge simply from the compounded strategic decision making of large numbers of optimizing agents (Kohler and Gumerman, 2000; Winterhalder and Kennett, 2006:19). Even so, HBE may not be framed properly to answer many questions about the evolution of systems per se, only how human optimizers should organize their effort within the systems in which they find themselves. External change (e.g., climate change or catastrophic loss of populations) pose little problem for this explanatory framework, but internally generated (evolutionary) change is anathema.

A promising bridging approach is the recently developed theory of niche construction. Laland and O'Brien (2011:191) define niche construction as “the process whereby organisms, through their activities and choices, modify their own and each other's niches.” Upon reflection, it might seem obvious that spider webs, bird nests, and brick buildings serve adaptive purposes for their architects while also altering environments and creating new opportunities, dependencies, and constraints for themselves and other organisms. When considered as a co-evolutionary process in which people and other organisms iteratively alter the characteristics of their selective environment and experience changing selective pressures as a result, niche construction provides a formal way of studying human ecodynamic co-evolution. Within this context, Laland and O'Brien (2011) use the concepts of ‘cultural niche construction’ to refer specifically to the way that people modify environments, in part, on the basis of cultural beliefs and practices. Bruce Smith (2007) shows how the food production “revolution” can be understood as an outcome of human modification of environments that ultimately led to fundamental changes in human economies and organizations, though he explicitly tries to distance niche construction theory from the principles of human behavioral ecology.

We suggest that these two approaches, HBE and niche construction, are complementary and that they could be integrated into a more comprehensive theory of human ecodynamics. Even so, the reductionism inherent in the “ultimate” evolutionary logic guiding HBE and to a lesser extent niche construction is unacceptable to many scholars on theoretical grounds, especially in its neglect of symbolic or cultural considerations. From a practical perspective, behavioral and evolutionary reductionism may miss important structural causes conditioning macro-evolutionary ecological change. For behavioral ecologists, the position that such processes should be explained reductively is recognized as a methodological assumption (Winterhalder and Smith, 1992). Other theoretical traditions focus on examining structural factors that may guide the evolution of systems irrespective of or, more likely, in concert with the actions and motivations of strategic and evolutionarily designed agents within them. Prominent among these for ecological anthropology are historical ecology and resilience theory.