Today’s societies often operate under the assumption that education, hard work, and opportunity are the main drivers of upward mobility. Intelligence has traditionally been viewed as part of that formula as well, with decades of research showing that people who score highly on cognitive tests frequently go on to attain higher levels of education and more prestigious careers.
But a new study suggests the relationship between genetics and success may be more complex and more politically sensitive than many social scientists and decision-makers are comfortable acknowledging.
In research published in Scientific Reports, Dr. Petri J. Kajonius, a research psychologist at Lund University in Sweden, found that genetic factors explained most of the long-term relationship between IQ and later educational and occupational outcomes among young adults.
Using data from the large-scale German TwinLife project, Dr. Kajonius examined how cognitive ability measured at around age 23 related to socioeconomic outcomes four years later, including educational attainment, occupational prestige, and occupational socioeconomic status.
By comparing identical twins, who share nearly all of their DNA, with fraternal twins, who share roughly half, Dr. Kajonius was able to estimate how much of the relationship between intelligence and socioeconomic outcomes could be tied to genetics rather than environmental aspects.
According to the findings, genetic influences explained between 69% and 98% of the observed relationship between IQ and later socioeconomic status.
“Genetic factors further explained most of the IQ–SES association (69–98%), and genetic correlations between IQ and SES exceeded environmental correlations,” Kajonius wrote in the paper. “These findings seem to underscore the importance of researchers and policymakers to also consider genetic factors when examining the life outcomes of young adults.”
The findings step directly into one of the most controversial debates in modern science: how much of a person’s life trajectory is controlled by environment versus inherited biology.
Dr. Kajonius is careful not to frame genetics as destiny. Rather, the research argues that inherited traits may play a substantially larger role in educational and occupational outcomes than many public discussions typically acknowledge.
The study relied on data from TwinLife, a long-running German research initiative examining social inequality across the lifespan. The project tracks more than 4,000 families through repeated surveys and assessments.
For the analysis, Dr. Kajonius focused on adults aged 23 to 27. Participants completed standardized IQ testing and reported educational and occupational milestones.
The results showed a strong relationship between IQ scores at age 23 and socioeconomic outcomes several years later. Participants with higher cognitive scores generally achieved higher educational attainment and occupational status by age 27.
However, the most intriguing findings emerged when those correlations were separated into genetic and environmental components.
The study estimated the heritability of IQ at roughly 75%, while educational and occupational outcomes also demonstrated substantial heritable influences. Depending on the metric being analyzed, genetics accounted for the overwhelming majority of the observed connection between intelligence and socioeconomic success.
Environmental aspects still mattered, specifically in education, but their contribution to the IQ-to-SES relationship was significantly smaller than the genetic overlap identified in the analysis.
Dr. Kajonius provided several possible explanations for this overlap. One possibility is what he describes as “direct or biological pleiotropy,” in which the same genes affect both brain development and traits associated with success, such as motivation or behavioral tendencies.
Another possibility is a more indirect pathway: inherited traits that lead to higher cognitive ability, which in turn provide access to better educational and occupational opportunities.
The findings dispute simplified explanations of inequality that focus exclusively on social structures or environmental disadvantage.
Over the last decade, advances in behavioral genetics and large-scale genetic analysis have increasingly suggested that traits such as educational attainment, personality characteristics, and intelligence are all influenced, at least in part, by heredity.
At the same time, the field remains deeply controversial.
Critics have long warned that research on heredity can be misinterpreted, politicized, or used to support deterministic worldviews. Researchers frequently emphasize that heritability estimates apply to populations, not to individuals, and that this does not mean environmental interventions are irrelevant.
Even highly heritable traits can still be affected by culture, institutions, economics, and personal experience.
Because of that history, studies linking genetics, intelligence, and socioeconomic outcomes often draw accusations of promoting hereditarian thinking or echoing past eugenic arguments. Those concerns have also contributed to caution within the field itself, leaving some areas of the wider “nature versus nurture” debate comparatively underexplored.
“[An] individual’s future socioeconomic status (SES) has been reported to be robustly predicted by cognitive ability (IQ),” Dr. Kajonius notes. “However, research on the genetic and environmental underpinnings of this association in emerging adults remains limited.”
Importantly, the study does not argue that genes determine a person’s value, worth, or inevitable future. Dr. Kajonius also stresses that no single “success gene” exists.
Human outcomes remain extraordinarily complex, formed by countless interactions between biology, environment, institutions, and personal backgrounds. In fact, the study itself notes that IQ explains only a modest portion of overall socioeconomic variation.
The findings similarly complicate the assumption that children from wealthier families succeed solely because of privilege or inherited social advantage.
“The so-called ‘silver spoon’ isn’t as big as you might think,” Dr. Kajonius said in a press release. “Your home life also depends on your genes.”
Rather than portraying affluent children as inherently superior, the study points toward a far more layered reality in which inherited traits, family dynamics, academic access, and broader social conditions all interact over time.
Dr. Kajonius also acknowledged several limitations to the research. The analysis covered only a four-year period during early adulthood, leaving unanswered questions about how these relationships may evolve later in life. Parental socioeconomic status was also not directly controlled for in the primary analysis.
Twin studies themselves remain the subject of longstanding methodological debates, notably regarding shared environments and gene-environment interactions. Dr. Kajonius notes that reducing such complex biological and social processes into broad categories of “genes” and “environment” inevitably oversimplifies reality.
Still, the findings add to a growing body of evidence suggesting that differences in cognitive ability and life outcomes cannot be explained entirely by environmental factors alone.
Dr. Kajonius ultimately argues that broad institutional interventions, such as expanding educational availability, may not completely eliminate socioeconomic disparities because individuals are not psychologically identical.
“People are different – Genetic predispositions (i.e., individual differences) seem to play a role in individuals’ socioeconomic outcomes,” Kajonius concludes. “Failure to account for these well-replicated genetic influences in research may present the wrong conclusions for both the public and academia.”
“As a researcher, my job is to describe reality as accurately as possible. If we want to change society, we must, of course, understand the underlying assumptions.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com