A large study of twins brings new insights to the long-standing debate “nature versus nurture”suggesting that genetics may play a much bigger role in future success than many people imagine.
The researchers found that IQ measured at age 23 is strongly related to socioeconomic status at age 27, including education level, occupation and income. According to the study, a large part of this link appears to be influenced by genetics, not just the environment in which a person grew up, writes ScienceDaily.
The results come from Germany’s TwinLife project, a large long-term research program that looks at how genes and environment shape people’s lives over time.
The Twin Study: IQ and the Life Course
The research followed about 880 people, including identical and fraternal twins. About half of the participants were identical twins, who share 100 percent of their genes, and the rest were fraternal twins, who share an average of 50 percent of their genetic material.
Because these twins grew up in the same families, the researchers were able to compare how much of their differences were due to genes and how much to the environment.
Participants took IQ tests at age 23. Four years later, the researchers assessed their socioeconomic status based on factors such as education level, occupation and income.
The results were surprising. Estimates show that IQ is about 75% genetically determined. Also, the link between IQ and socio-economic status would be largely explained by genetic factors, between 69% and 98%.
“We knew this before, but this study shows even more clearly that we are influenced by our genes and become who we are to a large extent because of them”explains psychologist Petri Kajonius, author of the study published in Scientific Reports.
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The findings contradict the common idea that success depends mainly on whether one grew up in a wealthy or highly educated family.
“The so-called “silver spoon” is not as influential as one might think. The family environment is, in turn, influenced by your genes”explains Kajonius.
This does not mean that family background does not matter. Instead, research suggests that genetically inherited traits can influence how people react to opportunities, education, and life experiences.
The study also raises difficult questions about social mobility and public policy. If genetics strongly influence life course, it remains to be debated to what extent educational programs or social interventions can change a person’s long-term trajectory.
“The study shows that we are born with different genetic predispositions and that it is difficult to make lasting changes in this sense through public policy measures alone”the authors also show.
What the results mean for parents and young people
According to Kajonius, the results may even provide some form of reassurance for parents.
Many parents fear that mistakes in their children’s education can decisively affect their future. But the study suggests that parents may have less control over long-term socioeconomic outcomes than previously thought.
However, this does not mean that education or parental support does not matter. Well-targeted interventions can still help people succeed. But their influence seems to have limits in the face of deep, innate traits.
For young people, the findings could change the way they view careers and success.
Instead of focusing solely on status or income, Kajonius suggests that people may have more to gain by choosing fields in which they are naturally inclined and in which they can easily perform.
Important limitations of the study
The researchers also point out some limitations of the research. One of them is that the study did not directly control for parents’ IQ or socio-economic status. Another problem is the difficulty of completely separating genetics from environment, as they often interact.
For example, certain genetic traits may manifest differently depending on upbringing and living conditions. This interaction could lead to an overestimation of the genetic influence on IQ, possibly by as much as 15 percentage points.
Even with these limitations, the study adds important evidence to the idea that genetics play a major role in intelligence, opportunity and life course.
