London’s mayor, Boris Johnson, drew criticism late last year for saying that economic inequality can be attributed, in part, to IQ. “I am afraid that [the] violent economic centrifuge [of competition] is operating on human beings who are already very far from equal in raw ability,” he told an audience at the Centre for Policy Studies.

That’s a satisfying worldview for someone who is successful and considers himself unusually bright. But a quick look at the data shows the limitations of raw smarts and stick-to-itiveness as an explanation for inequality. The income distribution in the United States provides a good example. In 2012 the top 0.01 percent of households earned an average of $10.25 million, while the mean household income for the country overall was $51,000. Are top earners 200 times as smart as the rest of the field? Doubtful. Do they have the capacity to work 200 times more hours in the week? Even more doubtful. Many forces out of their control, including sheer luck, are at play.

But say you’re in that top 0.01 percent—or even the top 50 percent. Would you want to admit happenstance as a benefactor? Wouldn’t you rather believe that you earned your wealth, that you truly deserve it? Wouldn’t you like to think that any resources you inherited are rightfully yours, as the descendant of fundamentally exceptional people? Of course you would. New research indicates that in order to justify your lifestyle, you might even adjust your ideas about the power of genes. The lower classes are not merely unfortunate, according to the upper classes; they are genetically inferior.

In several experiments published in the Journal of Personality and Social Psychology, Michael Kraus of the University of Illinois at Urbana–Champaign and Dacher Keltner of the University of California at Berkeley explored what they call social class essentialism. Essentialism is the belief that surface differences between two groups of people or things can be explained by differences in fundamental identities. One sees categories as natural, discrete, and stable. Dogs have a certain dogness to them and cats a certain catness.

Researchers have found that people hold essentialist beliefs about generally biological categories such as gender, race, and sexuality, as well as about more cultural ones such as nationality, religion, and political orientation. Essentialism leads to stereotyping, prejudice, and a disinclination to mingle with outsiders. Kraus and Keltner wanted to know if we see social class as an essential category.

They started by developing a scale for measuring essentialistic beliefs about class. A diverse group of American adults rated their endorsement of such statements as “I think even if everyone wore the same clothing, people would still be able to tell your social class,” and “It is possible to determine one’s social class by examining their genes.” On average, people rated the items a 3.43, where 1 means completely disagree and 7 means completely agree.

Participants also gave a subjective rating, from 1 to 10, of their own social class rank within their community, based on education, income, and occupational status. The researchers found that higher social class was associated with greater social class essentialism. This pattern remained even after controlling for political orientation as well as objective measures of a participant’s income and education level, indicating that it’s one’s sense of being above or below others, not one’s actual resources, that drives the result.

Kraus and Keltner looked deeper into the connection between social class and social class essentialism by testing participants’ belief in a just world, asking them to evaluate such statements as “I feel that people get what they are entitled to have.” The psychologist Melvin Lerner developed just world theory in the 1960s, arguing that we’re motivated to believe that the world is a fair place. The alternative—a universe where bad things happen to good people—is too upsetting. So we engage defense mechanisms such as blaming the victim—“She shouldn’t have dressed that way”—or trusting that positive and negative events will be balanced out by karma, a form of magical thinking.

Kraus and Keltner found that the higher people perceived their social class to be, the more strongly they endorsed just-world beliefs, and that this difference explained their increased social class essentialism: Apparently if you feel that you’re doing well, you want to believe success comes to those who deserve it, and therefore those of lower status must not deserve it. (Incidentally, the argument that you “deserve” anything because of your genes is philosophically contentious; none of us did anything to earn our genes.)

Higher-class Americans may well believe life is fair because they’re motivated to defend their egos and lifestyle, but there’s an additional twist to their greater belief in a just world. Numerous researchers have found that upper-class people are more likely to explain other people’s behavior by appealing to internal traits and abilities, whereas lower-class individuals note circumstances and environmental forces. This matches reality in many ways for these respective groups. The rich do generally have the freedom to pursue their desires and strengths, while for the poor, external limitations often outnumber their opportunities. The poor realize they could have the best genes in the world and still end up working at McDonald’s. The wealthy might not merely be turning a blind eye to such realities; due to their personal experience, they might actually have a blind spot.

There is a grain of truth to social class essentialism; the few studies on the subject estimate that income, educational attainment, and occupational status are perhaps at least 10 percent genetic (and maybe much more). It makes sense that talent and drive, some portion of which are related to genetic variation, contribute to success. But that’s a far cry from saying “It is possible to determine one’s social class by examining his or her genes.” Such a statement ignores the role of wealth inheritance, the social connections one shares with one’s parents, or the educational opportunities family money can buy—not to mention strokes of good or bad luck (that are not tied to karma).

One repercussion of social class essentialism is a lack of forgiveness for criminals and cheaters. In one of Kraus and Keltner’s experiments, subjects read one of two fake scientific articles: One reported that we genetically inherit our work ethic, intelligence, and ultimately our socioeconomic status; the other held that socioeconomic status has no genetic basis. Then the participants read scenarios about someone cheating on an academic exam and rated how much they endorsed various punishments, including “restorative” ones such as community service and ethics training. Those who read the essay supporting essentialism showed more resistance to restorative punishments. “When people cheat the academic system they unfairly ascend the social class hierarchy,” Kraus says. Some of us might attribute a cheater’s seeming subpar intelligence or preparation or integrity to upbringing and see room for improvement. An essentialist will see bad genes. And if you think people can’t change, then there’s no use in trying to help them.

Kraus and Keltner think social class essentialism (and the historically even more harmful race essentialism) might push our justice system toward giving certain people long prison sentences instead of chances at rehabilitation. Spreading the notion that social categories are constructed could counteract the belief that lower-class people’s behavior is genetically determined, and it could also lead to greater support for drug treatment programs, affirmative action, Head Start, an increased minimum wage, and multiple other causes benefiting the less affluent.

Social class essentialism is basically inciting social Darwinism. This distortion of Darwin’s theory of evolution, in one interpretation, is the belief that only the fit survive and thrive—and, further, that this process should be accepted or even accelerated by public policy. It’s an example of the logical fallacy known as the “appeal to nature”—what is natural is good. (If that were true, technology and medicine would be moral abominations.) Social class essentialism entails belief in economic survival of the fittest as a fact. It might also entail belief in survival of the fittest as a desired end, given the results linking it to reduced support for restorative interventions. It’s one thing to say, “Those people can’t change, so let’s not waste our time.” It’s another to say, “Those people can’t change, so let’s lock them away.” Or eradicate them: Only four years ago, then-Lt. Gov. of South Carolina Andre Bauer told a town hall meeting that poor people, like “stray animals,” should not be fed, “because they breed.”

Kraus’ even more recent work, not yet published, goes beyond what high-status individuals believe in order to maintain the status hierarchy and explores what they do. Consider Congress. Members’ median net worth, in 2011, was $966,000. “They’re quite wealthy individuals,” Kraus says. “And because they’re wealthy they’re likely to engage in not only these essentialistic [mental] processes, but these people actually have power to enact laws to maintain inequality.” A top adviser to the U.K.’s education secretary just produced a report arguing that “discussions on issues such as social mobility entirely ignore genetics.” He claimed that school performance is as much as 70 percent genetic and criticized England’s Sure Start program as a waste of money. (As Scott Barry Kaufman, an intelligence researcher at NYU and the author of Ungifted, points out, “Since genes are always interacting with environmental triggers, there is simply no way to parse how much of an individual child’s performance is due to nature or nurture.”)

It may be easy to demonize upper-class politicians as out of touch. But given how easily Kraus and Keltner triggered social class essentialism in everyday Americans, and given the frequency with which we toss around terms like white trash, redneck, welfare queen, and (across the pond) chav, we might want to question the degree to which we all see status as a marker of a deeper identity. If you were born under other circumstances, your résumé might look very different. Privilege is often invisible, especially one’s own.