Tuesday, March 13, 2018

Genetics and Politics: A Review for the Social Scientist / Understanding differences in the genome can help identify why people who experience the same social environment physically perceive it and react to it differently

Genetics and Politics: A Review for the Social Scientist. Adam Lockyer and Peter K. Hatemi. In Oxford Handbook of Evolution, Biology, and Society, edited by Rosemary L. Hopcroft. DOI: 10.1093/oxfordhb/9780190299323.013.44

Abstract: Social scientists most often seek to empirically validate something already observed. Genetics identifies the unobserved. It provides a starting point to identify developmental pathways to preferences and behaviors. Understanding differences in the genome can help identify why people who experience the same social environment physically perceive it differently and react to it differently. The introduction of evolutionary theory, combined with methods and approaches from genetics, genomics, epigenetics, and molecular biology, has substantially changed the way in which social scientists explore and understand the development and maintenance of political values and behaviors. This chapter reviews findings from recent empirical and theoretical studies that have explored how genetic factors account for some part of why people differ politically.

Keywords: evolution, genetics, politics, attitudes, nature–nurture

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Nature, Nurture, and Politics

Since antiquity, philosophical debates have persisted as to whether it is nature or nurture that guides humanity. Today, we know, it is neither alone. Empirical findings across the natural and social sciences have provided compelling evidence that simplistic monocausal biological or environmental explanations for complex social traits are implausible. Instead, in order to have any true understanding of the origins and development of complex behaviors, we must focus on developmental processes that treat nature and nurture as interdependent (Lewkowicz, 2011).
Universal human traits and variance in such traits, including political values, are the product of the complex interaction between inherited physiology, socialization, and personal experiences. The process is not linear but, rather, recursive. Individuals’ inherited biology and experiences influence how they interconnect with their social world, which in turn activates, represses, and conditions psychological and biological responses (McDermott & Hatemi, 2013; Ridley, 2003). These then, of course, condition, alter, and change one’s experiences, including the environments people select into and the way people see, perceive, and interpret their social world, and thus how they react to it and how others react to them—creating an indefinite circle of development.
Not all are on board with this position. Indeed, remarkably, after thousands of years and overwhelming evidence to the contrary, the nature versus nurture dichotomy continues to doggedly persist in modern academic and public discourse (Eagly & Wood, 2013). Although it is difficult to find a scientist who believes any complex social trait or behavior is all nature, there are still social scientists who argue that it is all nurture (Charney, 2008a; Shultziner, 2013). Nevertheless, when it comes to the majority of the social sciences, the tide has turned. During the past 40 years, research has eroded (p. 282) the belief in such a dichotomy, and during the past 10 years in particular, this erosion appears to be leading to a complete collapse of the division (Hatemi & McDermott, 2012a).
Today, most social scientists are no longer asking whether genes influence political behavior. Instead, the discussion has moved on to asking why, what, when, and to what extent particular environments trigger or repress specific genetic processes (Benjamin et al., 2012; Hatemi, Byrne, & McDermott, 2012; Hatemi & McDermott, 2012a). A surging wave of energy has been directed at elucidating the influence of genetic factors on political attitudes and behaviors, including vote choice (Dawes & Fowler, 2009; Fowler, Baker, & Dawes, 2008; Fowler & Dawes, 2008; Hatemi, Medland, Morley, Heath, & Martin, 2007; Littvay, Weith, & Dawes, 2011), political ideologies (Alford, Funk, & Hibbing, 2005; Hatemi, Eaves, & McDermott, 2012), political attitudes (Alford et al., 2005; Cranmer & Dawes, 2012; Hatemi, Funk, et al., 2009; Hatemi & McDermott, 2016; Hatemi et al., 2010, 2014; Smith & Hatemi, 2013), party identification and identity (Dawes & Fowler, 2009; Fazekas & Littvay, 2012; Hatemi, Alford, Hibbing, Martin, & Eaves, 2009; Settle, Dawes, & Fowler, 2009; Weber, Johnson, & Arceneaux, 2011), political trust (Merolla, Burnett, Pyle, Ahmadi, & Zak, 2013; Ojeda, 2016; Oskarsson, Dawes, Johannesson, & Magnusson, 2012; Sturgis et al., 2010), political participation (Dawes et al., 2014; Fazekas & Hatemi, 2016; Fowler et al., 2008; Fowler, Dawes, & Settle, 2011; Klemmensen, Hatemi, Hobolt, Petersen, et al., 2012), sophistication and efficacy (Arceneaux, Johnson, & Maes, 2012; Klemmensen, Hatemi, Hobolt, Petersen, et al., 2012; Klemmensen, Hatemi, Hobolt, Skytthe, et al., 2012), and aggression and conflict (McDermott, Dawes, Prom-Wormley, Eaves, & Hatemi, 2013; McDermott & Hatemi, 2017; McDermott, Tingley, Cowden, Frazzetto, & Johnson, 2009; Stam, Von Hagen-Jamar, & Worthington, 2012). A number of reviews on evolutionary theory, genetic theory, and what genes are and how they operate, in addition to primers on advanced statistical and molecular genetics, are present in the social science literature (Barkow, Cosmides, & Tooby, 1992; Fowler & Schreiber, 2008; Hatemi, Byrne, et al., 2012; Hatemi & McDermott, 2011a, 2011b; Hibbing & Smith, 2007; Lopez, McDermott, & Petersen, 2011; Lumsden & Wilson, 1981; McDermott & Hatemi, 2013; Medland & Hatemi, 2009; Rushton, Littlefield, & Lumsden, 1986; Smith, Larimer, Littvay, & Hibbing, 2007; Verhulst & Hatemi, 2013). Also, funded workshops on genetic analyses are available annually through multiple mediums specifically tailored for social scientists.
The creation of the link between genetic inherence and social traits promises to be one of the most exciting and productive avenues of social science inquiry in the 21st century. It has not gone unnoticed that over the course of the 20th century, the natural sciences greatly outperformed the social sciences. King (2011) noted,
Fifteen years ago, Science published predictions from each of 60 scientists about the future of their fields. The physical and natural scientists wrote about a succession of breathtaking discoveries to be made, inventions to be constructed, problems to be solved, and policies and engineering changes that might become possible. In sharp (p. 283) contrast, the (smaller number of) social scientists did not mention a single problem they thought might be addressed, much less solved, or any inventions or discoveries on the horizon. Instead, they wrote about social science scholarship, how we once studied this and in the future we’re going to be studying that. (p. 719)
Between 1900 and 2000, aerospace went from having never successfully flown an airplane to putting a man on the moon. Medical science extended the average human life expectancy by decades. Engineering went from steam engines to bullet trains, the Internet, and artificial intelligence. Even meteorologists, formerly the subject of jokes, now reliably and consistently forecast the weather. In contrast, the social sciences have made relatively little progress. Economists have been studying the causes of the Great Depression for almost 100 years but could not predict the 2007–2008 global financial crisis. Experts in international relations have been studying the causes of World War I but were totally blindsided by the fall of the Berlin Wall and modern Islamic terrorism. Others have been studiously researching American voting behavior for 100 years, but before late spring 2016, few believed, much less predicted, that Donald Trump would win the Republican nomination and the presidency.
We are, of course, being too hard on our discipline. The natural sciences have many advantages in comparison. One that we might be able to leverage, however, is a universal theory of behavior—evolution. In the natural sciences, contradictory theories tend not to survive long, even between different branches (e.g., chemistry and geology). They tend to be lightning rods for empirical researchers who rush to resolve the debate. The speed of publication, the focus on evidence, the willingness to let go of established wisdom, and the focus on innovation and discovery comprise the nature of the natural sciences. The same has not been true of the social sciences. Keynesian and Hayekian economic theories exist side by side, like realism and liberalism continue to coexist in international relations, and rational choice and structuralism in political science. The contending schools of thought in the social sciences more often speak past one another rather than to each other, which retards the advancement of disciplinary knowledge and often impedes interdisciplinary research.
Genetically informed social science research has the potential to cut through many existing cleavages. It may provide social scientists with a common foundation on which explanations of social behavior can be built. Empirical research in genetics demands replication, and it is in a constant and dynamic state of advancement, with new methods and approaches developed almost daily. Inclusion of genetics requires social scientists to move beyond all-encompassing and often conflicting paradigmatic worldviews and begin to have the same conversations the natural sciences were having throughout their hyperproductive 20th century. Already, genetically informed research is having an impact on many areas of political science research, including providing rational choice theories with some hint of where preferences originate, which has long puzzled the field (Benjamin et al., 2012; Camerer, Loewenstein, & Prelec, 2005; Cesarini, Dawes, Johannesson, Lichtenstein, & Wallace, 2009; Dawes et al., 2012; Hatemi & McDermott, 2011b; Hibbing, Smith, & Alford, 2013).
(p. 284) Considering the importance and promise of genetic approaches to the social sciences, this chapter offers a review for those new to the area. In so doing, an extensive list of references is provided to assist readers in delving deeper into the area.

The Why, What, and How of Genetics and Politics

Genetics offers a suite of methods to better explicate the pathways that lead to variation on traits of interest. That is, genetics provides tools to better understand why individuals differ and why people are also the same. They do not replace other methods but provide additional information. The rapidly expanding research on genetics and political science can be categorized a number of different ways. The most popular have been either by research method (e.g., classical twin studies vs. genome studies; see Hatemi, Dawes, Frost-Keller, Settle, & Verhulst, 2011) or by traits (e.g., political attitudes vs. vote choice; see Hatemi & McDermott, 2012a). In this chapter, we take a more functional approach by cataloging the recent literature on the topic and dividing it along lines of its overall “research objectives.” Simply stated, we categorize the literature by studies that ask “Why?” “What?” or “How?”
A first avenue of research has asked “why” the human genome has evolved to exercise an influence on political traits. This research avenue has primarily been theoretical and deductive and has employed evolutionary reasoning and primate observations to deduce the origins of genetic influences on political attitudes (Lockyer & Hatemi, 2014; Lopez et al., 2011; Petersen, 2010; Proctor & Brosnan, 2011). Generally, this research agenda assumes that modern humans have evolved to display political traits; because these traits have been “selected in,” then they must have served a purpose through human evolutionary history. This assumes that modern political interactions are reflections of tribal living. Hence, deductively reasoning as to “why” humans have evolved to have genetically influenced political traits may point empirical researchers toward why human systems are similar across diverse ecologies.
The second research grouping has attempted to determine “what” political traits (e.g., voting) are genetically influenced. This research is akin to identifying omitted independent variables on discrete political behaviors and more than the other research agenda has been responsible for showing that significant biological influences exist on political traits. Not only has it been extremely successful in identifying that genetic influences operate on a range of different political beliefs and behaviors but also, perhaps more important, this research agenda has encouraged the wider exploration of the effects of neurobiology, hormones, and other physiological characteristics on political traits (Hatemi & McDermott, 2011b, 2012a; Hibbing et al., 2013; McDermott & Hatemi, 2013; Mooney, 2012; Shenkman, 2016; Tuschman, 2013; Weeden & Kurzban, 2014).
Finally, there is a nascent stream of research that is inquiring into “how” and which genes influence specific political traits. This research is attempting to reveal the (p. 285) neurological and chemical pathways that link the genes and regions of the genome with the eventual political trait. Researchers have used advanced imaging technology and samples of people with brain damage or abnormalities to attempt to trace neurological and neurochemical pathways from DNA to the expressed political trait. This research is in its early stages and holds much promise of bringing true discovery back into the social sciences.

Why Do Our Genes Influence Political Traits?

Since the mapping of the human genome, there is a growing body of evidence supporting the thesis that certain inherited genetic markers are the product of human’s evolutionary need to overcome problems related to group living (Lockyer & Hatemi, 2014; Lopez et al., 2011; Petersen, 2012, 2015). Long before empirical approaches became available to identify and quantify genetic influences, however, scholars approached the question of the relationship between genes and political traits by using deductive reasoning and evolutionary theory (Barkow et al., 1992; Cosmides & Tooby, 1997; Faulkner, Schaller, Park, & Duncan, 2004; Hammond & Axelrod, 2006; Hibbing & Smith, 2007; Kurzban & Leary, 2001; McDermott, 2004; Tooby & Cosmides, 1988, 2010; Wrangham, 1999). They sought to explain why political attitudes and behavior appear universally across human societies and why humans’ DNA evolved to have such traits at all.
The empirical record shows that all human societies revolve around communal living. Communities provide many advantages to individuals, including greater security, safety, support, and a division of labor between rearing children and gathering food. Communal living, however, also creates problems that early humans would have needed to solve, such as ensuring that everyone has an opportunity to pass their genes on to the next generation and that communal resources are fairly distributed. There is no one universal solution to these problems. Humans have proven themselves to be immensely malleable and have organized communities ranging from strict hierarchical structures to more egalitarian pluralistic collectives. In an evolutionary sense, the specific political solutions were not universal: Hierarchical communities have been equally as successful as egalitarian ones, but everyone within the tribe must subscribe to the same solution.
This is the evolutionary reason why people have evolved to have such strong political attitudes. Political attitudes are different from attitudes in general. Political attitudes “are not just how an individual feels about something but how individuals believe others in society ought to feel and behave” (Lockyer & Hatemi, 2014, p. 552). A person may have an attitude toward ice cream or music without any expectation that other people ought to possess the same attitude. The same is not generally true regarding political issues, such as abortion, punishment for norms violators, marriage, immigration, or how resources are allocated.
Humans have been shown to have particularly strong political attitudes on the domains of sex and reproduction, child-rearing, in-group/out-group relations, defense, fairness, survival, cooperation, security, and affiliation (Apicella, Marlowe, Fowler, & Christakis, 2012; Barkow et al., 1992; Cosmides & Tooby, 1997; Fowler & Schreiber, 2008; (p. 286) Hatemi & McDermott, 2011a; Hibbing & Smith, 2007; Kurzban & Leary, 2001; Lockyer & Hatemi, 2014; Lopez & McDermott, 2012; Lopez et al., 2011; McDermott & Hatemi, 2013; Miller, 2011; Petersen, 2012; Petersen & Aaroe, 2012; Petersen, Sell, Tooby, & Cosmides, 2012; Smith et al., 2007; Thayer, 2000; Tooby & Cosmides, 1988, 2010; Tuschman, 2013). People inherit the propensity to have political attitudes, but cultural and environmental factors will shape how these political attitudes are defined in an almost infinite number of ways. For instance, historically, immigration has been an emotionally charged political issue across time and between countries. The issue of “foreigners” was as politically charged in ancient Rome as it is in modern-day Britain. However, individuals can link immigration back to either the domain of “out-group” relations or “fairness.” Either way, individuals are likely to feel particularly emotional about the political issue, but they may well fall on different sides of the debate. The context, labels, and policies will change between countries and across time, but the most politically charged debates will often be those that can be traced back to one of the domains people have evolved to be the most important to group living.
From an evolutionary perspective, observed preferences and behaviors are not simply the result of the current environment. Like the rest of the human anatomy, the brain is a product of evolution. Over the course of thousands of generations, the human brain has evolved certain universal structures and functions to overcome recurring social dilemmas. That is, the architecture of the human brain produces certain universal systems, including those of cognition, emotion, preference formation, and need for security. These evolutionary structures are different from instincts in that they are cognitive and emotional pathways for processing information. That is, instincts are evolved reactions to stimuli, such as the fight-or-flight response to being surprised. Human behavioral predispositions, on the other hand, are the product of the human brain having evolved to process information in particular ways. For example, humans have a strong predisposition to the in-group compared to the out-group. However, how these groups are defined is a social contract and is completely malleable between individuals and over time.
In this view, modern-day political choices are more complex versions of the basic problems that have surrounded group living since the inception of humanity. Modern national defense and foreign policy issues and decisions to use military force are only recent reflections of tribal decision to protect the in-group from outsiders. The political and technological context may be dramatically different; however, how people frame the decision and the thought process that goes into the decision-making are the product of thousands of years of evolution. Today’s political attitudes surrounding child-rearing, sexual liberties, and marriage are the modern-day equivalent of the ancestral need to ensure access to mates and have offspring. The strong opinions on immigration reflect modern insecurities, but those insecurities are seated in the primitive need to balance protecting against unknown and unfamiliar others with the potential gains from diversity (e.g., genetic diversity[strengthening the mating pool], resource security, social norms differences, and pathogen protections). The economic issues of today (e.g., taxes and welfare) address the same core concerns of how to share resources in a community.
(p. 287) Certainly, the issues of today are more complex. Institutions, political parties, social groups, nation states and non-state actors, cultural and historical conflicts, elites, communication, transportation, technology, and globalism, among many other factors, make social interactions much more complicated than those our ancestors confronted. Also, the relative importance and nuances of political issues differ depending on different environmental conditions, social forces (e.g., social customs, traditions, and material constraints), local histories, and ecology. Nevertheless, the fundamental psychological processes used to make political choices today are not so different as they were in the Pleistocene. The labels and rhetoric of issues change across cultures, time periods, and countries; modern economic and political structures levy their own influence on the mass public’s understanding and organization of political thoughts; and the channels through which preferences are conveyed in large modern societies are much less personal and direct than in the past; however, the underlying issues that are important, including family, reproduction, defense, and resources, remain the same. That is, when humans have to make decisions on how to manage societal life today, they are relying on the same cognitive and emotional mechanisms to address the same fundamental problems that their ancestors relied on.
Genetics has brought with it a unifying theory of human behavior—evolution. The natural, medical, and physical sciences have a variety of microtheories, but all behavioral studies rest on a theory of evolution. Whether or not evolutionary theory becomes the core theory of behavior in the social sciences remains to be seen; however, due to its capacity to lead to new discoveries, advances, and scientific progress, it may be the vehicle by which the social sciences catch up to the natural sciences.

Identifying Genetic Influences

A second research agenda emerged in conjunction with the first, albeit more slowly, and it is empirical in nature. This research approach has sought to reveal what political traits are genetically influenced. Utilizing a classical twin design (CTD), Lindon Eaves and Hans Eysenck (1974) performed the first study to find that political traits are genetically influenced. The CTD compares the co-twin correlations between monozygotic (MZ; identical) and dizygotic (DZ; fraternal) twins. MZ twins develop from a single fertilized egg and, thus, share their chromosomal sequence. DZ twins grow from two separate eggs, fertilized from two different sperm, and share approximately half their genetic inherence, similar to non-twin siblings. This combination of twin pairs provides researchers with the ability to control for comparable familial influence. The underlining assumption is that, on average, MZ and DZ co-twins grow up exposed to equivalent familial experiences, such as having the same meals, living in the same neighborhood and at the same time, attending the same schools, and having similar peer groups. This allows researchers the ability to partition out factors common to the twins (genes and familial factors) and unique to the twins (personal experiences).1
(p. 288) Heritability estimates focus on individual differences; that is, they do not explain the value of a trait but, rather, the difference of values within a population. Thus, when a heritability estimate of 0.35 is reported for sex attitudes, for example, it is not that genes explain 35% of sex attitudes; rather, it is that 0.35 of the variance, or individual differences in sex attitudes within the population, is accounted for by the aggregate of genetic influences. That is, heritability estimates provide a population estimate of how people differ. They are not an estimate of the percentage within any given individual that is accounted for by genetic factors. They are not to be interpreted to mean that for every person in the population, 0.35 of a person’s attitudes are due to genes.
Eaves and Eysenck (1974) measured social and political attitudes on a wide range of different issues, including the death penalty, unions, unemployment, and abortion. Their pioneering study supported the proposition that individual differences in political attitudes were a function of both biology and environment. Despite their work being published in Nature, it was more than a decade before such findings received much attention. Indeed, the work most often credited as the foundational piece in the genetics of politics literature was published 12 years later in Proceedings of the National Academy of Sciences. Along with his advisor, Lindon Eaves, Martin et al. (1986) substantially extended the earlier work with much larger samples, a wider range of political orientations, and more complex analyses that included the role of assortative mating. This work found that differences in political orientations were genetically influenced to a larger extend that previously thought.






Figure 14.1 Sources of individual differences on political traits.

The first genetically informed research to make a serious impression on the social sciences, however, came much later, in 2005, when John Hibbing and John Alford (Alford, Funk, & Hibbing, 2005) republished results from Eaves and Martin’s works (Eaves et al., 1997; Eaves & Eysenck, 1974; Eaves, Eysenck, & Martin, 1989; Eaves et al., 1999; Martin et al., 1986) in the American Political Science Review. Following Alford et al. (2005), twin studies emerged as the most popular methods for exploring genetic influences on political beliefs and social behaviors. Taking up the mantle from Eaves and Martin, Hatemi, Fowler, and Dawes have perhaps led the second wave of research to rediscover the usefulness of twin studies in the research on political traits (Cesarini et al., 2008, 2009; Cranmer & Dawes, 2012; Dawes et al., 2014; Dawes & Fowler, 2009; Fazekas & Hatemi, 2016; Fowler et al., 2008; Fowler & Dawes, 2008, 2013; Fowler et al., 2011; Hatemi, 2013; Hatemi, Alford, et al., 2009; Hatemi, Eaves, et al., 2012; Hatemi & McDermott, 2014; Hatemi, McDermott, Eaves, Kendler, & Neale, 2013; Hatemi, Medland, & Eaves, 2009; Hatemi et al., 2014; Hatemi & Verhulst, 2015; Klemmensen, Hatemi, Hobolt, Petersen, et al., 2012; Klemmensen, Hatemi, Hobolt, Skytthe, et al., 2012; Littvay et al., 2011; Loewen & Dawes, 2012; Loewen et al., 2013; McDermott et al., 2013; Oskarsson et al., 2012; Smith et al., 2012; Smith & Hatemi, 2013; Verhulst, Eaves, & Hatemi, 2012; Verhulst & Hatemi, 2013; Verhulst, Hatemi, & Eaves, 2012). Many critical discoveries have come from these works, summarized in several review articles (Hatemi, Dawes, et al., 2011; Hatemi & McDermott, 2012a, 2012b, 2016; Hibbing, Smith, Peterson, & Feher, 2014) (p. 289)
First, the heritability of political traits differed greatly within and across traits (Figure 14.1 provides a summary of results from published articles). On the higher end of the scale, roughly 50% or more of the variation in political knowledge, social trust, ideology, participation, and interest can be attributed to genetic influences, comparable to cognitive ability, perceptual accuracy, and prosociality (58–70%). More than 40% of the variation in attitudes on sex topics (e.g., gay rights), religious items (e.g., Bible truth), economic items (e.g., welfare), defense items, freedom and liberties, and efficacy can be attributed to genetic influences, whereas less than 30% of the variation regarding out-group and punishment attitudes can be attributed to genetic influences. On the low end are ethnocentrism ( < 20%), civic duty ( < 15%), and party identification ( ~ 5%). These findings have been replicated across multiple countries and decades. For example,  <20 a="" across="" and="" been="" civic="" countries="" decades.="" duty="" example="" findings="" for="" have="" href="http://sci-hub.tw/view/10.1093/oxfordhb/9780190299323.001.0001/oxfordhb-9780190299323-e-43#oxfordhb-9780190299323-e-43-bibItem-696" id="ref_oxfordhb-9780190299323-e-43-bibItem-696" identification="" multiple="" party="" replicated="" these="">Hatemi and colleagues (2014)included samples spanning from the 1970s through 2010 from Australia, Denmark, Sweden, and the United States and found that genetic influences on political attitudes and social, economic, and defense ideologies, in addition to authoritarianism, were similar across time and cultures, whereas social and environmental factors manifested themselves differently according to local ecologies and constraints. Second, genetic influences remained even when the most sophisticated modeling techniques were used, such as those that included all types of relatives; addressed the effects of assortative mating; included specific environmental or socialization factors, or used multivariate models, which included other psychological traits.
Assortative mating is important to consider because both heritability and social transmission approaches, for example, assume that mating is randomized. This is (p. 290) critical because studies have shown that one of the strongest correlates of long-term mates is political ideology (Alford, Hatemi, Hibbing, Martin, & Eaves, 2011; Eaves & Hatemi, 2008; Eaves, Hatemi, Heath, & Martin, 2011; Klofstad, McDermott, & Hatemi, 2012, 2013; Martin et al., 1986). That is, even controlling for ideological convergence and social homogamy, research has shown that people tend to select mates who share their positions on political orientations and issues (Luo & Klohnen, 2005; Luo & Zhang, 2009). If there is assortative mating on a trait of interest and that trait is genetically influenced, then the inherited genetic influences will be underestimated, while environmental and shared experiences will be overestimated. This is true because if parents assort on the trait of interest and the trait is genetically influenced, parents will be more genetically similar for that trait; when they produce offspring, the shuffling of genetic code produced by sexual reproduction will result in less genetic variation among DZ twins (or any full sibling types) than assumed. Thus, DZ genetic similarity will be on average greater than the 0.5 assumed in twin models, leaving MZ/DZ co-twin observed trait differences to be explained by a smaller amount of genetic differences. Such a circumstance would mean twin models underestimate genetic influences. Extrapolating this to a population, the higher the proportion of mates who share genes for a trait, the closer the DZ correlation will become to the MZ correlation and the more the genetic variance of this trait will be underestimated.
This means that the influence of genetic factors in determining the political attitudes of individuals begins even before fertilization. Hatemi and colleagues (Eaves & Hatemi, 2008; Eaves et al., 2011; Hatemi et al., 2010; Keller et al., 2009) addressed this issue by using extended kinship models based on data collected from twins’ parents and twins’ spouses. This technique resulted in genetic influences accounting for even more of the variance reported on political attitudes and ideologies. Assortative mating may well be the single most important factor in determining an individual’s political attitudes because it precludes and determines genetic transmission, parent–child socialization, environment, and personal experiences (Eaves & Hatemi, 2008).
A number of studies have also explored the importance of specific environments. Littvay and Fazekas included twin-specific and shared environments and also election-specific factors, whereas Hatemi focused on critical life events (Fazekas & Hatemi, 2016; Fazekas & Littvay, 2015; Hatemi, 2013; Littvay, 2012). These researchers found that social factors have an important role in shifting the relative import of both genetic and environmental influences. When social forces (i.e., social and material constraints) are absent, genetic influences emerge as more important in how people differ. When personal life events or social forces are overwhelming or constraining, genetic influences become all but absent in explaining variation. For example, genetic influences on individual behavior will be visible in highly disciplined religious communities. Critically important, however, is that when the constraining crisis recedes, or social influences allow people to differ, individuals revert back to their initial disposition and genetic influence re-emerge as important.
One of the first substantive challenges to the research stream on what political traits are genetically influenced was the idea that the heritability of political orientations (p. 291) might simply be an artifact or spurious, deriving from some covariate, particularly personality. On the surface, this idea seemed plausible; individual differences in personality are an equal function of genes and environment. However, despite much discussion and the widespread belief that personality is strongly related to political traits, the empirical record shows otherwise. Most personality traits are neither consistently nor significantly related to political values. The major exceptions are that the personality trait of “openness to new experiences” is positively associated with socially liberal attitudes, whereas “conscientiousness” is positively associated with socially conservative attitudes. Even here, the correlations between the two are modest. Nevertheless, a series of multivariate genetic studies have found that the overwhelming majority of genetic influences on political traits are unique to the traits themselves and not accounted for by personality, morality, or other psychological constructs (Dawes et al., 2014; Hatemi & Verhulst, 2015; Oskarsson et al., 2015; Smith, Alford, Hibbing, Martin, & Hatemi, 2017; Verhulst, Eaves, et al., 2012; Verhulst, Hatemi, & Martin, 2010).
There are of course many challenges to the methods and assumptions of twin studies. We refer readers to published critiques and exchanges for greater details (Alford, Funk, & Hibbing, 2008a, 2008b; Charney, 2008a, 2008b, 2012; Fowler & Dawes, 2013; Hannagan & Hatemi, 2008; Hatemi et al., 2010; Hibbing et al., 2013; Littvay, 2012). We simplify the criticisms to one dimension here. The concern largely revolves around reductionism in some form or another. Some of the loudest critics argue that one cannot assume general similarity in environments, make on-average estimates, partition any trait variance into a discrete amount of genes or environments, and so on with or without bounds or confidence intervals. These criticisms, although they seem reasonable, are criticisms of science in general and are specious. In truth, no credible scientist actually challenges such concerns on a theoretical level. However, science is naturally reductionist. Until a better approach than empirical estimates come along, we are left with estimates with confidence intervals and other bounds to graph or display probabilities and possibilities.
The modern scientist knows that it is not valuable to simply ask if nature or nurture determines the form of a particular trait, or even how much each factor contributes to a trait. Although these are often portrayed by the methodologies available in quantitative behavioral genetics and molecular biology, science has progressed to the point that it is known that any dichotomy does not stand up to either empirical or conceptual scrutiny. Quantifying the extent to which nature or nurture contributes to a trait, however, provides a critical starting point because these two classes of factors are both always present. They are interactive and operate differentially during different developmental stages and life experiences. Therefore, the methods used are simply a first step to answer how our traits develop and how they are maintained over the life course—that is, how it is that genetic, social, and all other factors, including people and populations, interact to produce behavioral traits.
Unfortunately, there is no single method to model the complexities of life—that is, the “life” package in R does not yet exist to perfectly model development, nor do we have the data to do so. However, a number of extensions to classical twin approaches (p. 292) have begun this process. Longitudinal twin studies have the advantage of being able to track sources of variation across different life stages. These studies have found that the political attitudes of MZ and DZ co-twins were no different until they left home (Eaves et al., 1997; Hatemi, Funk, et al., 2009). That is, in childhood, there were no genetic influences present on political traits. Yet, when children left home, MZ co-twins continued to show strong correlations, whereas DZ co-twins’ political attitudes diverged. This suggested that after leaving the parental home, DZ co-twins selected into or found themselves experiencing different environments and social influences at greater rates than did MZ co-twins. Thus, the home environment repressed individual differences, and genetic influences only emerged once children left home. These developmental studies have only begun, and there are few methodologies and data to fully explore the developmental trajectories of genetic and environmental influences.

How Do Genes Influence Political Traits?

Although twin studies provide valuable insights into the latent causal genetic pathways, they cannot identify the specific genetic and neurobiological markers and associated systems that operate on political traits. Thus, molecular genetics has become an emerging area of research that attempts to identify how genes influence traits through their neurological and neurochemical pathways. In contrast with the first empirical avenue of research that is largely focused on revealing if and to what extent latent genetic factors influence individual differences in political and social traits, this avenue of research is concerned with process tracking and identifying the specific genetic variants, how they work, and how social and environmental factors influence and are influenced by these traits, directly and indirectly. (For a detailed review on how genes operate with specific pathways for political traits, see Bergner & Hatemi, 2016; Hatemi, Byrne, et al., 2012).
This avenue of inquiry has only recently begun and thus there are only a handful of empirical studies. To date, two approaches have been used. The first method is an inductive empirical approach. This method involves scanning the entire genome for a genetic marker or chromosomal region that shows a correlation with the political trait of interest (Hirschhorn, 2009; Rietveld et al., 2013). Like most inductive studies, this method’s strength lies in there being no prior assumptions made on the underlying causes. That is, no prior knowledge is assumed on the underlying biological pathways or causes of a political trait. This avenue is in fact one of true discovery because it identifies causal pathways that were previously unknown. Every region of the genome is tested, and strict statistical significance thresholds are maintained to allow for the multiple testing of the millions of genetic markers. Being genome-wide, this method is the most empirically rigorous of the two methods, and before any general conclusion can be reached, independent replication is required. For example, in the first genome-wide linkage study of political attitudes, Hatemi, Gillespie, et al. (2011) used a sample of 13,000 Australians and identified several regions containing methyl-d-aspartate, serotonin, glutamate, dopamine, olfactory, and G protein-coupled-related receptors that potentially corresponded (p. 293) to liberal and conservative political beliefs. However, two follow-up studies applied genome-wide association analyses and found no markers related to political ideologies or attitudes that reached a significance level of 5 × 10–0.8 or better (Benjamin et al., 2012; Hatemi et al., 2014). That is, the markers were not replicated in independent samples.
The challenge of genome-wide analyses is that they require extremely large samples in order to obtain significant results. This is because the influence of any single genetic marker on a complex social or political trait, such as vote choice or ideology, is infinitesimal. Indeed, Rietveld et al. (2013) showed that for complex traits such as educational attainment, samples into the hundreds of thousands are required to identify individual genetic markers that are statistically significant. As such, although genome-wide analysis is a highly promising avenue of research, there is is currently an insufficient amount of data to accurately perform this analysis. Thus, technological and methodological advances and additional data in the future are bound to turn this avenue of research into one of the most important in the field.
A second gene mapping technique relies on a priori knowledge to identify likely candidate genes—that is, those genes that can be expected to be associated with specific political and social traits based on prior associations with similar or root traits. The “candidate marker approach” has proven to be more popular than genome-wide studies. This should not be surprising because it reduces costs, saves time, and exploits the greater availability of data. Fowler and Dawes (2008) relied on previous evidence that identified two genetic polymorphisms, monoamine oxidase A (MAOA) and 5HTT (serotonin), as being associated with prosocial and antisocial behavior. MAOA, for example, correlated with prosocial behavior, and a lack of MAOA appeared to be significant in antisocial behavior. Treating voter turnout as a prosocial behavior, they found that the “high” allele of MAOA and the “long” allele of 5HTT were related to higher voter turnout. However, these markers were only significant in specific socializing conditions, such as religious service attendance. That is, genetic markers previously associated with sociability required some additional social priming in order to operate on voter turnout. Several follow-up articles presented some evidence of replication for serotonin having a role in participation (Dawes & Fowler, 2009; Deppe, Stoltenberg, Smith, & Hibbing, 2013; Fowler & Dawes, 2008, 2013).
Although there have been some hints at novel pathways using candidate gene studies, most of these studies account for very small variance and few have stood up to replication (Duncan & Keller, 2011). At this early stage, no single genetic variant has been found to account for a significant portion of a discrete political trait with a strong degree of certainty. The lack of clear associations is partly a reflection of the fact that this area of genetic research remains in its infancy.
These findings, however, are only a first step. Research has begun to link differences in the gene sequence, genetic expression, hormones, and neurological function, which will lead to a better understanding of the full developmental and biobehavioral pathways to political preferences and actions. Endocrinological, psychopharmacological, and neurochemical studies have observed the role of hormones in regulating the release and modulation of peptides (e.g., vasopressin, serotonin, dopamine, and oxytocin), which in turn (p. 294) alter neurological function identified through event-related brain potentials. Functional magnetic resonance imagining and lesion studies show that activity in the brain is triggered by subcellular activity and specific genetic mechanisms under specific environmental conditions. This research has been conducted on a wide range of traits correlated with political traits, including emotion regulation and recognition (Canli & Lesch, 2007; Uzefovsky, Shalev, Israel, Knafo, & Ebstein, 2012), social affiliation (Walum et al., 2012), cognition (Meyer-Lindenberg et al., 2006), anxiety (Myers et al., 2014), moral judgments (Koenigs et al., 2007), power seeking (Madsen, 1985, 1987), stereotyping of out-groups and in-groups (Hart et al., 2000), trust (Kosfeld, Heinrichs, Zak, Fischbacher, & Fehr, 2005), self-awareness (Gusnard, 2005), empathy (Carr, Iacoboni, Dubeau, Mazziotta, & Lenzi, 2003), and decision-making (Sanfey, Rilling, Aronson, Nystrom, & Cohen, 2003).

What Have We Learned?

Perhaps the greatest challenges to the integration of genetics into the social sciences are dispelling myths and the need to find a common language. The vast majority of degree programs in the social sciences do not require basic science courses; thus, social and natural scientists start with large knowledge gaps. Most PhD graduates in social sciences have only a basic knowledge of how genes operate and, as such, many interpret genetic research as arguing that human social behavior is purely deterministic, which is absurd. On the other hand, those entirely focused on genetics or biology often miss the subtleties of the social constructs they seek to understand. For instance, neuroimaging, physiological, and other biological studies have often mistakenly treated party identification, ideology, attitudes, and vote choice as synonyms when, in fact, they are well known to be quite different constructs. Party identification, for example, is more often about identity than values, whereas discrete attitudes tend to reflect beliefs. So, for the social scientist unfamiliar with genetics, what are the takeaways? What have we learned in the past 40 years at the intersection of genetics and politics?
First, political traits are not simply the result of modern institutions, governments, economies, or circumstance. Rather, humans have evolved to be political in order to address the needs, constraints, and benefits that can be derived from communal living. Politics is a fundamental part of what it is to be human—not in a colloquial sense but in an evolutionary sense.
Second, traits result from the interaction of both genetic and environmental influences through developmental pathways. Genetic factors only operate in conjunction with environmental ones. There is no “gene for” any complex trait. That is, there is no “political” gene. No complex social trait will ever be only nature or nurture. Genetic influences on the predilection to exhibit any political or social trait will be indirect and result from the aggregate effects of the interaction of thousands of genes interacting with immeasurable immediate and long-term environmental conditions and experiences that change during the life course.
(p. 295) Third, genetics is as much about human universals as it is about individual differences. Understanding the cognitive and emotional mechanisms will allow researchers to map the basic architecture of how humans operate, such as universal brain function, the role of specific hormones, and the downstream cognitive and emotional processes humans use to make decisions and form preferences. At the same time, although all healthy people use the same neural architecture, people differ, even if so slightly in their genetic makeup, resulting in differences within those cognitive, emotive, and perceptual pathways, which will result in trait variation. People are different. We are different at the genetic level, and we are different socially. Environmental forces will not have the same impact on all individuals. Genetic differences will not have the same result across environments. For example, only some soldiers from the same unit who fight in the same battle develop post-traumatic stress disorder; others repress the experience, and still others write books and easily recount the battle’s details. Even when raised in the exact same environments, there will be differences in individual responses to stimuli. The overwhelming majority of research on political traits treats people as the same (rational actors) and views socializing agents and experiences as the source of individual differences. This simply cannot continue under the weight of the evidence to the contrary. The hundreds of millions of combinations of polymorphic markers that differ between people in conjunction with social experiences lead to differences in perception, cognition, emotion, reasoning, preferences, and eventual behavior. In short, the one tenet that buttresses many of our core theories in social science, the blank slate, is no longer valid.
Fourth, although there are major individual differences within societies, there are scant differences across them. People are different. Peoples are the same. Less than 1% of DNA differs between individual humans (Redon et al., 2006), and more than 85% of those differences exist within populations (Jorde & Wooding, 2004). In other words, there are greater genetic differences door-to-door than continent-to-continent. Molecular genetic research affirms that we are mostly the same across ethnicities. This simple fact has arguably led to increases in tolerance and changes in policy. We can think of no better or more politically salient example than the issue of equal rights for lesbian, gay, bisexual, and transgender (LGBT) individuals in Western democracies. Since Hamer, Hu, Magnuson, Hu, and Pattatucci (1993) implicated genetic loci for homosexuality, the narrative changed from one of deviant behavior and choice to one of inherent disposition (Hatemi & McDermott, 2011c, 2012a). Subsequently, elite views, including state and US Supreme Court decisions, changed, which filtered down to the public’s change in its view of sexual preference. Today, the trend is acceptance and increasing tolerance.
Fifth, identifying genetic systems and their related perceptual, physical, cognitive, and emotional processes has led to novel hypotheses regarding the nature and manifestation of political preferences and behavior. For example, we have learned that smell and pathogen avoidance, and their genetic mechanisms, have a significant role in determining why individuals differ in their attitudes about immigration (Hatemi et al., 2013; McDermott, Tingley, & Hatemi, 2014; Navarrete & Fessler, 2006). Such findings could not have been obtained using social- or environmental-only approaches to behavior.
(p. 296) Finally, in a world of both genes and environments, environments become more—not less—important. Genetic theory provides a vast new avenue to explore environmental influences. It is not that people are born liberal or conservative or any other political orientation. Nor are they simply socialized as so. Genes rarely, if ever, have a direct role in any complex trait. Rather, individuals with certain genetic profiles will be more or less likely to find themselves engaging in or seeking certain experiences and then perceiving and reacting to experiences in a certain way. The sum of those interactions alongside all the differences in constraints, opportunities, and people with whom they engage, among others, and simple happenstance will result in certain probabilities of, for example, joining the military, turning out to vote, being influenced by a candidate’s speech, or even running for office (Fazekas & Hatemi, 2016). In this sense, sociology is even more important in explaining why people differ. Understanding what a gene is, which genes are activated or repressed, and how they inform behavior requires a greater, not lesser, understanding of the social environment. By including genetics, the environment represents much more than the observed stimuli humans experience. Rather, the concept of the “environment” expands beyond social experiences but includes the in utero environment, internal cellular environments, and all the experiences that occur across the lifespan. That is, environment includes everything inside and outside the body both before and after an individual is born. It also includes the environments of our ancestors. Differences in the individual’s circumstances, such as war or having a child, can have effects on both the internal mechanisms and the person’s overall behavior, but these experiences can trigger entirely different genetic mechanisms that may or may not work together or in opposition to one another. Environments trigger and restrict gene expression, and without these triggers, genetic influences are not realized. In short, without biology, we cannot fully explain why people differ under the same environmental conditions, and without the environment, we cannot explain why people with the same DNA differ in behavior outcomes. As such, we have much more to do to reinvest in understanding socialization, and life experiences, than ever before.

Conclusion

Now, perhaps more than at any point in the past 200 years, the social sciences are back in a time of discovery. King’s (2011) observation of how we viewed our future 60 years ago does not have to be how we view our future today. We rarely have had the means of true discovery in the social sciences. Rather, social scientists have most often sought to empirically validate something already observed. Genetics identifies the unobserved. It provides a starting point to identify novel developmental pathways to preferences and behaviors. Understanding differences in the genome can help identify why people who experience the same social environment physically perceive it differently and react to it differently. It allows for the exploration of individual trajectories. This line of research (p. 297) has only begun, and we are excited to see genetic and other biological methods and approaches further incorporated into the study of political traits.


Notes:

(1.) In addition to the classical twin design, a number of studies have reported similar finding using twins reared apart and adoption studies (Abrahamson, Baker, & Caspi, 2002; Bouchard & Loehlin, 2001; Bouchard, Lykken, McGue, Segal, & Tellegen, 1990; Bouchard & McGue, 2003; Oskarsson et al., 2015; Tesser, 1993).

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