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How much does genetics affect political beliefs? Does it even matter?

Twin studies, the bedrock of genetic studies of political attitudes, may not be as solid as once thought

Prabarna Ganguly

National Human Genome Research Institute

Global politics are in a profound state of change. People around the world are standing up to the aging tenets of conservative democracy and demanding ideological debates on social issues like immigration, healthcare, social reform, and establishment of a national identity. The rise of the ‘-isms’: tribalism, populism, and nationalism, have many concerned, angered, and even ecstatic as it challenges the status quo. Still, people today are more politically educated and engaged than ever before. But why are we all so different in our political attitudes, and where does this difference come from? 

For the greater part of the 20th century, political behaviors and preferences were largely considered to be socially determined. Social scientists emphasized nurture over nature, arguing that politics are too recent a phenomenon to be influenced by evolutionary forces. In another aisle, life scientists were busy focusing on improving human health, uninterested in venturing into the biology of social behavior.

But it did not take long for large shifts to appear in the biological sciences. In the late 1960s, researchers began to consider the interaction between genes and environment as a possible basis for all social behaviors. Social scientists also started agreeing that gene-culture co-evolution was more likely to be accurate rather than favoring either nature or nurture alone.  It is against this backdrop that researchers began addressing the role of genetics in forming our political beliefs, terming the field “genopolitics”. They relied on a unique research paradigm: twin studies

A picture of Francis Galton, founder of eugenics.

Francis Galton, inventor of twin studies and father of eugenics.

Our curiosity with twins is well-documented. In 1875, Sir Francis Galton, the father of eugenics, wrote The History of Twins, the first-known work that used twins to study the heritability of traits. To put it mildly, his analysis sparked debate since he suggested that England’s “chief men of genius” were products of good breeding (nature) as compared to good rearing (nurture). Unsurprisingly, Galton’s methods were less than sound. His sample size was small, with only 35 sets of twins, and composed entirely of upper-class individuals. There was also no control group, which would have been non-twin siblings or even fraternal twins. Despite these flaws, twin studies took off, and became a staple for testing nature-nurture debates. 

The modern-day classical twin study design relies on studying twins raised in the same family environments. This acts as a control for both genetic background as well as shared environment early in life. Identical twins develop from an egg fertilized by a single sperm, which splits in two a few days into development. This is why identical twins are expected to share all of their genes, and any differences between these twins can be attributed to non-shared environmental influences. Fraternal twins are a result of two separate eggs being fertilized during the same pregnancy, and therefore share only about 50% of all their genes. 

Researchers’ study the similarity between sets of identical and fraternal twins for a specific feature. If both sets share similarities, that percentage is attributed to the environment. But any extra likeness between the identical twins is considered to be due to genes, and not the environment. 

Numerous papers have used twin studies to assess political party affiliations, attitudes and inclinations. Many of them have suggested that genetic factors play a role in how political ideologies are formed. And when the largest of these studies on political beliefs says so, people listen. 

That study was published in 2014 by Hatemi and colleagues in the journal Behavioral Genetics.  They analyzed a combined sample of over 12,000 twin pairs from Australia, Denmark, Hungary, Sweden, and the US, and interviewed them every ten years over the course of four decades. Both identical and fraternal twins were included. The study found that approximately 40% of political ideologies, such as liberalism, conservatism, individualism-collectivism and economic egalitarianism were heritable.

This means that 40% of how twins responded to the questionnaires may be explained by genetics. Simply put, "heritability" estimates how well we can predict a trait (in this case, political beliefs) from genetics alone. But this would be true only if researchers understood all the relevant genetic effects. 

A painting by Norman Rockwell shows a husband and wife arguing over preferred political candidates while a child sits on the floor crying.

"Breakfast Table Political Argument" by Norman Rockwell

Norman Rockwell Museum

In an effort to do so, the researchers also aimed to find genes involved in the formation of such complex a behavior but did not find any genetic markers of significance. This means that even if genetics plays a role in forming political ideologies, the what and the how is still unknown.   

So, 40% of our political beliefs is informed by our genes. Case closed, right? Well, not exactly. Here is the catch: twin studies may not be as reliable measures of heritability as they seem.   

Twin studies make a number of assumptions. One is the assumption of "random mating," which assumes that people tend to choose partners who are different from each other. If people did partake in non-random mating, such as mating with people only in their town, fraternal twins would share a greater percentage of their genes than expected.    

The underlying genetic analysis used with twin studies makes the assumption that if something has a genetic cause, it must be inherited from your parents in a manner that follows Mendel’s simple laws of inheritance.  However, this is not always the case. 

One such example is the case of epigenetics. Epigenetics is a biological process that controls how our DNA is interpreted, i.e., how genes are expressed, without changing any DNA sequences. Normally, genes have epigenetic "marks," which alter their expression. These imprints exist before an organism's reproductive cells mature. Once matured, the imprints are erased from eggs and sperms, so that a new pattern of imprinting can occur with each generation. However, sometimes they can escape the resetting process and are passed down from parent to offspring. This kind of inheritance is unpredictable and does not follow Mendel’s laws. Hence the epigenetic outcomes can be difficult to predict, and the results of the analysis may be incorrect.      

There is also the assumption that genes and the environment make only separate and distinct contributions to a trait, whereas it is becoming increasingly clear that the relationship is bidirectional. Environments can have an active effect on how genes are expressed, and genes may have moderate effects only under specific environmental conditions. 

This inevitably leaves us with a “chicken-and-egg” question. Do genes predispose us to ideological stances, causing us to prefer absorbing certain information and not others, or are social environments the main influencers? Or are they both inextricably linked?   

Peter Beattie, Assistant Professor at the Chinese University of Hong Kong, articulates the complexity of the issue in a 2017 paper

“A child born in the United States with a generations-long right-wing pedigree, whom we would expect to have whatever genetic endowment produces a predisposition to right-wing ideas, would merely have a tendency to develop right-wing ideology; that tendency may go unexercised (or if exercised, unrealized) if the child were to grow up surrounded exclusively by left-wing ideas from friends, teachers, media, and political elites.”

Ultimately, until analysis of twin studies can incorporate the complexities and nuances of genetic and environmental factors, it's likely that twin studies are insufficient to impart any relevant insights on the social dimensions of a complex phenomenon like political beliefs. Being marked by large assumptions that limits its usefulness — it's unlikely that twin studies will result in drawing any trustworthy genetic conclusions.