We have detailed our use of Tinbergen’s Four Questions (Plus One) and the role it plays in our curriculum. Beyond our basic educational goal of teaching the application of evolutionary theory to research questions, the framework facilitates a few of our secondary goals. Namely, it successfully dispels the misguided notions underlying hyperadaptationism and genetic determinism; it permits for the reconciliation of genetic and cultural concerns under the umbrella of gene–culture coevolution; and it inclines students toward a broad question-based approach to research that transcends disciplinary boundaries.
One recurrent critique of the application of evolutionary theory to the study of humans—particularly research from the subdiscipline of evolutionary psychology—is the reduction of all traits to their functional adaptation. These attacks come not only from members of the social sciences who have not yet embraced an evolutionary approach (Davies 1996; Lloyd 1999) but also from other evolutionary theorists (Gould 1991; Lewontin 1998; Panksepp and Panksepp 2000; Smith et al. 2001). Likewise, some critics have pointed out that just because you can demonstrate that a trait is adaptive does not mean it is an adaptation (Laland and Brown 2002). Indeed, one of the great strengths of evolutionary theory is its unwavering rules regarding the costs and benefits associated with each trait. But, as Tinbergen’s model reminds us, this is not the only consideration that an evolutionary thinker should have in mind.
Certainly, many traits, if not the vast majority of them, are adaptations whose ultimate causation is enormously enlightening, but it is short-sighted to ignore the other processes that may have contributed to its current state. Such a perspective also ignores how traits may arise that are non-adaptive (i.e., selectively neutral) or even maladaptive. We ask students to use the rest of Tinbergen’s Four Questions (Plus One) to think critically about adaptationist hypotheses. The personality module provides a variety of good opportunities for this:
Proximate explanation: Higher handgrip strength is predictive of more sexual partners in males (Gallup et al. 2007). But this is in large part because handgrip strength is governed by the testosterone system, as are many other traits that are considered physically attractive by females (Gallup and Frederick 2010).
Phylogenetic explanation: Dodo birds were exterminated rapidly by newly arrived explorers because the absence of predators on the island of Mauritius left them with a species-specific personality lacking in fear.
Ontogenetic explanation: Habitual aggression may seem out of place in broader society, but it can be an adaptive response to a stressful upbringing (Belsky et al. 1991).
Cultural explanation: Plenty of behavioral tendencies that are socially learned have an adaptive value (i.e., bearing a fitness advantage in the local environment), but others are merely socially reinforced.
With a framework in hand that consistently reminds them of these considerations, the students are better equipped to develop non-adaptive hypotheses. In fact, many final projects exhibit this approach, and the studies designed by students usually provide a sophisticated test of adaptive value.
Many people believe that a heritable trait implies that there is a 100% correspondence between one’s genetics and the emergent phenotype. The interaction between genes and environment during trait development is relatively intuitive and can be easily explained. How it works at a proximate level, though, is a little more challenging for students to grasp. Harder still is reconciling this flexibility with adaptive traits, or, conversely, understanding how local adaption can arise despite a lack of genetic variation between individuals. Tinbergen’s model lays out the pieces of the puzzle in such a way that makes the idea more accessible. Clearly, genes (the proximate factor) are most directly responsible for the products that lead to a trait. Their function seems to be conditional on environmental inputs, however (development). If one were to search for inputs that are most influential in this process, they might want to look at those features that can influence the success of one phenotype in relation to its alternatives (ultimate mechanism). In this way, the students can see how the basic threads of evolutionary inquiry can combine to explain a relatively complex phenomenon.
Gene–Culture Coevolution vs. Cultural Relativism
Gene–culture coevolution is a framework for understanding the interactions between genetic and cultural factors (Richerson and Boyd 2004). It acknowledges that genes and culture can influence each other’s evolution; genes provide the raw material for culture to work with, and culture affects the environment within which genes compete. It also looks at the ways genes and culture interact during development. Proponents of the framework are careful to note that culture is not just any other environmental factor but one that is inextricably intertwined with the genetics it interacts with and influences. This singularity can be lost if cultural factors are allowed to disperse among Tinbergen’s other questions; thus, it is necessary for us to introduce the new question as we incorporate gene–culture coevolution into the later parts of our course.
Apart from this curricular consideration, the relationship between culture and evolution has ideological implications. Cultural relativists maintain that tendencies specific to a single culture should be observed only in the context of that culture and not subjected to comparisons across groups, which they fear are inherently normative (Segerstrale 2001). In a similar vein, some students see evolutionary perspectives on humans as reducing culture to mere biology and depriving it of the value and meaning that a cultural practice holds for those who adhere to it. Gene–culture coevolution, when utilized appropriately, takes note of the social processes that necessarily maintain cultural traits, allowing it to pay due respect to these aspects in addition to the psychological underpinnings of culture. Our fifth question attempts to incorporate this broadness of perspective into a model of evolutionary study.
Subject-Based Interdisciplinary Research
The research implications of a unified behavioral science are quite exciting. Breaking down the barriers between disciplines allows for the sharing of theoretical approaches, methodologies, and research designs. Most of all, it allows for a broadened perspective that takes on the subject without being limited by historical disciplinary boundaries. To illustrate, the two authors both study social behavior. Many fields have studied this topic, but each has its own starting point. Social psychologists tend to focus on contexts that influence social behavior, developmental psychologists on how individual differences in social tendencies arise, sociologists on group-level processes, economists on social attitudes during resource interactions, and so on. Each of these approaches brings its own deep literature that can easily inform the others, but only when disciplinary propriety is replaced with the pragmatic combination of all available materials to paint a complete picture of a trait.
Tinbergen’s Four Questions (Plus One) gives us a practically adisciplinary model for studying a particular human-related subject. It offers a guide for categorizing the aspect of a trait that a particular study may be addressing, highlighting its utility rather than its disciplinary origin. This approach is employed by many experienced scientists, but is not necessarily a part of undergraduate, or even graduate, training. Tinbergen’s Four Questions (Plus One), however, makes this approach intuitive and accessible to students from diverse backgrounds, making their approach to science flexible and increasing their potential for innovative thinking.