Both McDermott and Weinschenk stressed the dangers of misinterpreting their data.
McDermott wrote by email that her conclusion “does not mean that 60 percent of ideology comes from genetic factors but rather that around 60 percent of differences between people can be attributed to genetic factors.”
Weinschenk also added important caveats in an email:
When most people hear that something is heritable and when they hear a particular percentage, they often think it means that for each individual person, X percent of a given trait is influenced by their genes. For example, studies show that ideology is about 40 percent heritable. That doesn’t mean that 40 percent of Aaron Weinschenk’s ideology is shaped by genes and the other 60 is shaped by the environment. That’s not what a heritability estimate tells you. Rather, it tells you the extent to which differences between people are due to genetic factors.
In addition, Weinschenk noted that
just because something is influenced by genes, it doesn’t mean that the trait can’t be changed or that genes determine the outcome or trait. Genes can be expressed (or not) depending on the environment. For example, parents exert an important impact on ideology when people are living at home (and genes play a limited role at this time); when people “leave the nest” genetic predispositions then start to influence ideology (and family influences dissipate). People obviously have the same genes at all points in time, but genetic influences on ideology are expressed differently depending on the circumstances.
Given the contentious nature of these studies, McDermott, in a thoughtful email to me, described the thinking of those who are pursuing these lines of inquiry. For that reason I am going to quote her at length:
Genes influence those characteristics that would have made a difference in survival over long swaths of human history. Maybe not even a huge difference but even tiny differences add up to huge effects when multiplied by millions of people over millennia. That means that those characteristics that were most likely to make a difference in survival get preserved in genetic terms. Ideologically, what we have found over many years and many populations, tends to fall into a few basic categories: sex and reproduction; in-group defense and out-group discrimination; and resource allocation.
These underlying problems tend to affect all people over time in all situations. The specific issue might look different in a given time and place: in England in the 1840s, it might have looked like debates on pornography, prostitution and slavery or whatnot. In the U.S. now it may look like abortion, transgender bathrooms, immigration, war and welfare. But the underlying political and psychological issues they tap into are exactly the same. They get expressed differently but the underlying challenge to survival is the same.
How does this affect polarization?
McDermott observed that
The problem is that different people solve it differently and it would be one thing if everyone only solved it for themselves, but that is not how it works. People want everyone else to solve it the same way they do (pro-life, pro-choice, etc.). So, you ask why doesn’t it converge to universality over time like vision (all healthy people have two eyes etc.)? Well, likely because we need both tendencies in a population to survive (think of sex here: you need both male and female gametes to reproduce — if you eliminated all of one sex, survival would not happen. So, we need conservatives to compete and fight and defend against other people, animals, climate, etc. and we need liberals to cooperate and build houses and so on. If you only have one side, you would end up with a lot of annihilation.
In “Integrating Genetics into the Study of Electoral Behavior,” Carisa L. Bergner and Peter K. Hatemi, political scientists at Penn State, make the case that contemporary political issues can mirror prompts or situations encountered by human beings in the distant past:
Political traits, orientations, and ideologies, including those participatory acts such as voting, donating, and volunteering, encompass fundamentally the same issues of cooperation, reproduction and survival surrounding group life that confronted our ancestors.
Modern-day ideological issues, Bergner and Hatemi continue,
surrounding sexual freedoms, mores and parenting are reflected in the prehistoric need for access to mates and to ensure the survival of offspring; policy views on immigration are little different than the primal need to recognize and protect against unknown, unlike and potentially “dangerous” others; codified laws, policing and punishment are akin to dealing with mores violators in hunter-gatherer societies; taxes and social welfare programs essentially revolve around questions of the best way to share resources for group living; foreign policy and military are matters of protecting one’s in-group and defending against potential out-groups.
Bergner and Hatemi add:
While the labels and often meanings of issues change across time and cultures, and the medium through which preferences are communicated have changed from direct, immediate and interpersonal (e.g., person to person, group sanction, etc.) to indirect, latent and impersonal (e.g., internet, voting for someone you never met, etc.), the underlying connection between the core issues that are important to humans, revolving around cooperation, defense, reproduction, resources, and survival remain.
Stephen P. Schneider, along with Smith and John Hibbing, from the University of Nebraska, elaborate on the hereditarian case, challenging — in their 2018 paper, “Genetic Attributions: Sign of Intolerance or Acceptance?”— the view that “acceptance of genetic influences is believed to be associated with intolerance, prejudice, and the legitimation of social inequities and laissez-faire policies.”
Instead, using data from two nationally representative surveys of a total of 1,200 respondents conducted by YouGov, the three found, first, that “genetic attributions are actually more likely to be made by liberals, not conservatives”; second, that “genetic attributions are associated with higher, not lower, levels of tolerance of vulnerable individuals”; and third, that “genetic attributions do not correlate with unseemly racial attitudes.”
At the end of their paper, Schneider, Smith and Hibbing defend their stance:
In sum, we find that a key assumption underlying prevailing intellectual dogma — that compassionate, tolerant, racially enlightened individuals tend to deny that genetics is relevant to human variation — is factually inaccurate. Rather, people who accord genetics a role in explaining the different traits that humans possess are significantly more likely to be politically liberal; significantly more likely to be tolerant of homosexuals, drug addicts, the obese, and those with mental disabilities; and no more likely to hold unenlightened racial attitudes. Instead, those who believe traits are under personal control are the ones who tend to hold less tolerant attitudes.
In an email, Smith continued to press for his view:
Political orientation seems to be significantly heritable. There have been quite a few behavioral genetic (twin) studies looking at this and they’ve largely triangulated on estimates of roughly 40-60 percent of the population-level variance in ideology being attributable to genetic influence. That still leaves plenty of room for environmental influences, but these influences seem to be mostly idiosyncratic, i.e. the product of individual experience. Family (common environment) seems to have less of an influence, explaining maybe 10 percent of the variation, or even less. Other studies using different methodologies (e.g. adoption studies) seem to back up the general conclusion. Bottom line: the evidence that political orientation is significantly heritable is strong and consistent.
I also asked Smith about political polarization.
There’s good evidence that things like pro-sociality, including positive emotions directed toward others, are heritable, and it’s not at all controversial to say that in-group bias is part of our evolutionary heritage. Given that, it’s a good bet that some people are more predisposed toward being hostile and suspicious of out-groups and that those attitudes, like most attitudes, are a mix of the influences of nature and nurture. Map that psychology onto a political environment characterized by fraying institutions, decaying trust in centralized authority, and increasing demographic, religious, cultural heterogeneity and it’s a reasonable bet our stone age minds will be primed for polarization.
In a January 2021 article, “Are Moral Intuitions Heritable?,” Smith and Hatemi found that a unique method of measuring morality by forcing respondents to confront difficult life and death decisions produces some evidence of heritability. In their study, participants were shown “hypothetical short stories presenting a moral dilemma,” and were asked to respond “to each using an eight-point scale ranging from ‘Forbidden’ (1) to ‘Obligatory’ (8) with a middle point of ‘Permissible’ (4).”
The stories were designed to provoke strong reactions:
1. Killing and eating an injured boy so that you and another may survive; 2. Throwing one person overboard in order to save lives of self and others and 3. Killing a person in order to identify a vaccine that will save humanity.
Intense emotional reactions, Smith and Hatemi write, tap into “prepotent emotional response patterns that evolved as adaptations to group living” in the evolutionary past.
Ariel Malka, a professor of psychology at Yeshiva University, cautioned in an email that “when thinking about ‘liberalism’ and ‘conservatism’ in the American public, it is important to keep a couple of things in mind.”
The first is that “the meaning of these terms with respect to concrete policy content does in some important ways shift with the political context.” Second, and perhaps more important, Malka continued, “When it comes to the American public, ‘conservative’ and ‘liberal’ are best thought of as identities. Many politically engaged Americans think of themselves as either conservative or liberal, based on the prevailing social, cultural, and political implications of the terms.” Liberals and conservatives, he pointed out, “are motivated to act consistently with these identities to fit in and relate harmoniously with important others in their lives and to simply gain psychological value from expressing their identity.”