Most of the ecological challenges facing humanity today have arisen as the result of interactions between individuals, their societies, and the environment. This is true at many scales—from the world carbon emissions threatening the global climate to pollution of a nearby stream from backyard chemical runoff. Of course, one of these problems is easier to solve than the other—but why? And what can we learn from one that can guide our attempted solution to the other?
Beginning to answer such a fundamental question requires a consideration of theory. Theory allows us to draw general conclusions from a broad set of similar cases and use them to describe or predict outcomes in future instances. For example, we might ask what general lessons we can learn from traditional fishery management systems in pre-colonial Fiji; national environmental policy in Bhutan; or litter regulations in the United States. Below, we present a theoretical framework developed by Waring et al. (2015) to help clarify sustainability research and policy.
Cultural evolutionary theory provides a useful framework for studying social-ecological change and for designing policy to achieve sustainability in social-ecological systems. There are a number of reasons why this is so. Current social-ecological systems theory—or ‘sustainability theory’—does not consider or include endogenous cultural dynamics (Caldas et al., 2015). Instead, it is largely based on our understanding of ecological systems and ecological change, disregarding what we know about cultural dynamics from the outset. This is a big gap, because we now know a great deal about the complex internal dynamics of human culture.
Furthermore, human culture and cooperation are inextricably intertwined (Boyd and Richerson, 2009). This is crucial because virtually all challenges in achieving environmental sustainability are cursed with social dilemmas in which the best solution for individuals is not the best solution for the group. The solution to social dilemmas is, of course, cooperation. We now know a great deal about cooperation as well (Henrich, 2004; Nowak, 2006).
Finally, and most fundamentally, sustainability theory should be able to explain the emergence and persistence of sustainable states in social-ecological systems. Current theory in sustainability science focuses on the resilience of coupled human-natural systems, considered a type of complex adaptive system. This approach to social-ecological systems is mainly informed by our knowledge of ecological dynamics and does not include the cultural and social mechanisms and processes that operate independently of external drivers such as economic and ecological forces. Such processes include fundamental social factors such as identity formation and the inheritance of beliefs, values and preferences, which influence human decisions and actions throughout life. Cultural evolution is useful here, too, because cultural evolution is generally modeled using tools from evolutionary game theory that describe the requirements for a given behavior, such as a cooperative environmental behavior, to become an evolutionarily stable strategy. Thus, the tools of cultural evolution are well suited to describing conditions for the invasion (emergence) and stability (persistence) of sustainable behaviors—and that is what is most lacking from sustainability theory.
Cultural evolution is a simple concept with a few important elements. Evolution, in general, carries three requirements—variation, inheritance, and selection. Cultural evolution is a description of how culture changes over time as a result of these requirements. Although genetic evolution operates on genetically-encoded traits, cultural traits—such as behaviors, customs, and beliefs—are encoded in human minds. Cultural traits vary, and naturally, different cultural traits result in different outcomes for those who adopt them. When those outcomes influence how often those traits spread through imitation and other mechanisms, they undergo a type of natural selection. Usually bad ideas don’t catch on. However, cultural inheritance is very different from biological inheritance. Genetic inheritance is typically proceeds via the passing of genetic information from parent to offspring. This is called “vertical” inheritance, and genetic vertical inheritance is the result of reproductive choices of the parent. By contrast, with cultural evolution, the recipient of adaptive information typically initiates cultural transmission—we imitate individuals and traits we deem successful or somehow worthy. We constantly, and strategically, copy adaptive behavior from others. For instance, we often imitate our peers through “horizontal” cultural inheritance.
Scientists in many disciplines use cultural evolution to explain patterns of change in culture over time. Importantly, cultural evolution tends to occur at a faster rate than biological evolution—meaning that human societies adapt to environmental changes more quickly through social and behavioral change than through genetic adaptation. Rapid cultural adaptation is crucial to the formation of human societies. When a human population inhabits a particular environment, individuals gain a rich knowledge of the best natural resources, types of shelter, food processing and survival strategies. This adaptive information accumulates over the generations, so that individuals benefit from many lifespans’ worth of costly learning. As a result, human lifestyles, institutions, and behaviors are often very well-adapted to managing their natural environments. Cultural evolution helps us understand this accumulated cultural adaptation and is, therefore, useful in solving social-environmental problems.
An important aspect of cumulative cultural adaptation is the role of the group. Although some culturally learned behaviors are adaptive for individuals, others are advantageous for the groups in which those individual reside. Groups are an important and central feature of human life everywhere. Groups may be civil, military, religious, social or economic in nature, but they are often small (less than 200 people) and share a common goal or social identity. But, groups vary, as do their behaviors, rules, and systems for organizing themselves to accomplish shared tasks. Differences in the cultural traits between groups provide another opportunity for natural selection to operate. Of course, groups with traits better suited to their environments or to group competition tend to prosper and spread while others decline. However, group-level selection does not function only through demographic change such as group formation, growth, and dissolution, but also includes the effects of differential imitation and migration between groups. If a certain group is imitated more than others, the cultural traits of that group spread. So just as warfare can cause selection for improved military strategies, economic competition between companies can cause selection for improved business strategies. Both types are considered part of the simple and ubiquitous process of cultural group selection (Richerson et al., 2014).
Group-level selection is important for another reason as well—it is the most general force for the emergence of cooperation. When individuals compete, individually adaptive behaviors proliferate. In the environmental domain, this often means individuals extract more resources than is best for their group or the longevity of the resource. But when groups compete, cooperative and coordinated groups win and group-functional behaviors proliferate. In the environmental domain, group functional behaviors will often include resource conservation, because groups who exhaust resources, or who waste energy over internal resource conflict, fare more poorly than those who simply conserve and share. We are so accustomed to living with group-functional traits that we may rarely perceive them. But, cultural group selection is a potential cause of the cooperative traits that we see in society every day, such as charitable donations, taking turns, politeness norms, queuing behavior, team sports, and military strategy, to name just a few. For an extensive review of the evidence for cultural group selection, see Richerson et al. (2014).
Of course, in real life, individuals compete within teams even while teams compete to win. How can we predict the results of evolution then? Worse yet, in real life, there are often many more than two relevant levels of organization. Individuals reside in towns, towns in states, states in nations and nations join multinational alliances. Then there are households, corporations, and sports leagues. How can we possibly predict human behavior if evolution happens on all those levels simultaneously? Multilevel selection theory gives us the conceptual tools to begin. Multilevel selection theory provides statistical methods to track evolution across multiple levels simultaneously (Okasha, 2006). Using these tools, it becomes possible to follow the action and ask “where is evolution happening the most?” or more precisely, “is there a dominant level of selection?”
If selection between groups is stronger than selection between individuals within groups, we should expect group-functional behavior to emerge, and vice-versa. By empirically estimating the dominant level of selection, scientists and practitioners can gain insight into the dynamics of the social systems in which they work. Are cooperative, group-functional behaviors likely to emerge? Perhaps, if groups are strong, varied, compete regularly, and are keenly aware of each other’s strategies. Will a certain policy be adopted by a given organization? Perhaps not, if there are only a few organizations that exhibit only a little trait variation who do not pay close attention to the matter, and the benefits and costs of the policy are hard to determine.
All of this leads to a simple conclusion: if we want to explain the existence of a particular behavior, we need to identify the level of selection most likely to have produced it. Assuming that the behavior was culturally selected, what level of organization would have most likely been responsible? Although there is no guarantee that cultural change is due to selection, it may often be. Thus, by identifying the level of selection most relevant for a given trait, as well as the processes of variation and transmission that influence it, we can gain a robust understanding of its historical development and likely future trajectory.
The strength of cultural multilevel selection as a theoretical framework is demonstrated by its ability to both describe the underpinnings of events in the past while also allowing generalized lessons to predict potential outcomes in the future. To demonstrate the framework, we turn to Fiji, Bhutan, and the United States.
In pre-colonial Fiji, generally speaking, people survived by subsistence fishing. People were organized by family connections into clans, which in turn were organized into chiefdoms that held exclusive territories. Because subsistence fishing is labor-intensive, individuals tended to minimize their harvesting effort while satisfying the needs of their household. At the chiefdom level, selection likely favored rules to prevent overharvesting because of the need to have plentiful fish stocks in periods of upheaval, such as attempted invasion by neighboring chiefdoms or tropical storms. Moreover, evidence suggests that war between villages tended to be settled in favor of the defending villages, creating a selection for laws within chiefdoms to sustain their populations from the fisheries within their own territory and avoid engaging in conquest.
The historical resilience of the Fijian social-ecological system becomes apparent when we consider the disruption following colonization. Once Fiji was opened to a global fishing market, new incentives emerged to maximize harvests, while the old chiefdom system of governance was supplanted by the nation-state. In pre-colonial Fiji, fishing restrictions tended to help chiefdoms, and chiefdoms were likely the dominant level of selection for fishing rules generally. Meanwhile, overharvesting behaviors were minimized. After colonization, as the social controls of the chieftains were eroded, the dominant level of selection for fishing behavior changed from chiefdom to individual harvester. Individual harvesters, incentivized to maximize their harvests by the nation-state’s response to the global market, tended to overharvest and as a result have entered an ecological crisis. The history of fishing restrictions in Fiji shows how characterizing the dominant level of selection provides a way to hypothesize more accurately about the influence of policy changes across organizational levels.
A parallel case is Bhutan’s national environmental policy. Historically, Bhutan has faced a series of direct and indirect external threats and pressures, which have tended to accelerate the emergence of solidarity and a strong social identity. In response, the Bhutanese government has fostered a distinct religious and cultural identity through the encouragement of Buddhist influence in daily life. Strong social solidarity has included a Buddhist philosophy, environmental values, and the institution of Gross National Happiness (GNH)—instead of the widely-used Gross National Product (GNP)—as the primary indicator of national wellbeing. With this framework as the primary indicator of national success, development and economic activity have placed significant emphasis on sustainable use of natural resources and protection of environmental features, even when such considerations may inhibit economic growth.
Changes in the levels of selection are observable in each of the major shifts in Bhutanese culture in recent history. Before unification, competition between ethnic groups fueled warfare and led to higher rates of resource extraction. However, the persistence of existential threats at a national level led to the development of a national identity and the emergence of a monarchy, unifying disparate communities. With this consolidation came less autonomy at the individual and community levels, but also less warfare and greater cooperation. Unification also solidified a governance system based on Buddhist beliefs and ethics, which in turn led to the creation of the GNH model. Importantly, had external threats not driven Bhutan to unify politically, it appears that the GNH and related environmental conservation policies would never have emerged.
Describing Bhutan’s development in terms of multilevel selection is useful—but what can we predict about its future? One important trend could be the recent transition from monarchy to parliamentary democracy. This institutional shift—the product of cultural transmission—could lead to the development of political parties that may shift the dominant level of selection, in terms of policy, to the partisan level instead of the national level. If parties cooperate within themselves but compete in parliament, there could be serious implications for Bhutan’s future sustainability-oriented efforts, along with other changes. On the international level, however, the strength of cultural transmission will determine if other countries—or perhaps other groups at different scales—copy Bhutan’s unique practices.
Another useful example comes from the development of litter mitigation policy in the United States. Crucial to this case study is the appearance of competing, overlapping organizations—in this instance, private corporations and public government. Here the multilevel selection framework can be applied to both types of organization, revealing how their historical interactions created the conditions we see today.
With the widespread use of disposable packaging, especially for foodstuffs marketed to buyers for consumption in vehicles, came litter. Littering poses a classic social dilemma because individuals face negligible consequences for littering, while society as a group incurs a substantial cost from the aggregate result—trash everywhere. Policy responses to such a problem often vary greatly, making them ripe for selection. Two different types of organization—private corporations and public government—responded to the littering problem in different ways.
For democratic governments in the United States—particularly at the municipal and state levels—a number of policy options are available to tackle litter. Banning or limiting the production of disposable packaging, which constitutes the bulk of litter, is relatively inexpensive; managing and collecting litter from the environment is substantially more costly. Therefore, it is cheaper and easier for governments to create policy attempting to prevent litter at the source—the producer. However, for corporations that profit from selling products delivered in disposable packaging, such a policy would be problematic.
Although states and municipalities moved to implement bottle deposit policies and other measures to curb litter by limiting waste production, a number of food and beverage companies banded together to form a public advocacy supergroup, Keep America Beautiful, Inc. (KAB) to encourage individuals to take responsibility for their own cleanup. Waring and coauthors suggest that the resulting process followed an evolutionary course.
There are a number of selective influences at play in this example. Individuals cooperate through democratic governments to solve the problem, producing regulations that were mimicked by other municipal and state governments. The potential costs of reusable packaging incentivized corporations to cooperate to find a way to avoid those costs. The resulting industry supergroup, KAB, operated by creating pressure at the individual level to accept personal responsibility for the litter problem, thereby attempting to change cultural norms and lead to relaxed regulation at the corporate level. This example demonstrates that when different types of organization—such as corporations and governments—share a single environmental domain, the outcomes depend result from a coevolution of strategies between both organizational types. In this case, the best environmental solution, reusable packaging, was forfeited because corporations adapted more rapidly to their own challenge than citizens and governments did to theirs. As a result, governments at all levels now handle a greater cost of waste handling than they would otherwise have.
What these cases illustrate is the ability of cultural multilevel selection to draw generalized conclusions from different actual examples, and describe these lessons in such a way that they can be used to predict and potentially preempt related challenges in the future. Estimating the dominant level of selection for a given behavior or norm, while accounting for broader cultural context, is a proper first step for attempting to solve collective action problems related to sustainability. Context is key, however—for example, in Fiji, selection at the national level occurred weakened rules and social norms that encouraged resource conservation, while in Bhutan the opposite seems true. This is because Bhutan’s GNH is a national-level policy, while traditional Fijian fishing restrictions were at the chiefdom level. This difference explains why a similar selective regime—at the level of the nation—resulted in different conservation outcomes, and underscores the importance of determining where the strength of selection is greatest. Successful interventions must therefore respond to both context and selection.
The case studies of Waring and coauthors are meant to illustrate the role cultural multilevel selection might play in truly evaluating on-the-ground social-ecological systems and sustainability challenges. That task is the next step in developing a cultural evolution science of sustainability. However, the signature of cultural multilevel selection is very common. We can see it when we watch individual opinion and state policy feedback on each other in a cascade that results in a policy change at the federal level on issues such as same sex marriage, alcohol prohibition, or marijuana legalization (Tribou and Collins, 2015). We can see it in the spread of sports strategies between players and teams in national sports such as hockey and football. We can see it happen as costly voluntary environmental practices percolate through industries (Prakash and Potoski, 2006). And, we can observe the emergence of climate policy, such as carbon emissions regulations, as individual opinion shifts and policies spread between states and nations. In each of these cases, there are cooperative social dilemmas that make the best individual strategy conflict with the best group policy, but, despite the conflict, group-focused solutions can emerge and do. Cooperative solutions are not guaranteed, but applying cultural multilevel selection can help us understand how they emerge and guide us toward more effective interventions and more lasting solutions.
Ultimately, the value of cultural multi-level selection will be determined by its applicability and predictive power in disparate cases. As a theoretical framework, cultural multi-level selection provides a rubric for organizing causal processes that matter in the evolution of social-ecological systems. And, at its heart, there is a prediction of great importance. It is this: if the strength of selection on groups for resource conservation is stronger than the strength of selection on individuals for greater consumption, costly conservation practices and group-beneficial policies are likely emerge.
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