While we’ve debated “nature vs. nurture” for nearly a hundred years – since at least Francis Galton’s “Hereditary Genius” – the last few decades have shown that the answer is almost always C, “all of the above.” As recently as a few decades ago, conventional wisdom still held that:
- We’re all born with a finite amount of brain cells.
- They’re wired one specific way.
- And brain function deteriorates with age.
In short, prevailing wisdom dictated that we spent our lives losing brain cells – and connections – until finally, the brain simply breaks down. That all changed just before the turn of the century. In 1998, the Salk Institute’s Fred Gage and his team showed that the human brain can grow new cells – even well in adulthood.
This revelation, “neurogenesis,” paired with our better grasp of neuroplasticity, essentially quashed the nature vs. nurture debate.
Now, new research adds fresh insight to the existing literature. An international group of researchers sought to dig into the relationship between genetics and income. This paper, derived from a genome-wide association study (GWAS) of income, underscores the need for heightened scrutiny around how we think about genetic determinism.
Methodology
The researchers wanted to discover how genetic factors converge with environmental ones to shape income and socio-economic mobility. Using GWAS, the team examined millions of genetic variants across more than 668,000 individuals with European roots. As part of the project, the team included four income measures: individual, occupational, household, and parental income. This allowed the team to paint a better picture of income-related genetic influences.
By identifying genetic variants linked to income, the researchers sought to uncover the wider social mechanisms that drive income disparities and intergenerational mobility. What they found exposes the intricate interplay between genetics, education, health, and socio-economic outcomes.
Genetics, Income, and Health
The researchers singled out multiple genetic variants tied to income, though each had a small individual effect. While, individually, each variant barely moved the needle, taken together, these variants exerted an outsized influence on educational attainment, cognition, behavior, and physical health. Even so, the genetic overlap between income and health outcomes varied.
For example, higher incomes typically gave way to better physical health outcomes, such as reduced risks of hypertension and diabetes. However, some psychiatric disorders, such as schizophrenia and autism, showed opposing genetic correlations with income and educational attainment.
And in a twist worthy of a “Law & Order” episode, when the study’s authors compared siblings , they saw a notable drop – roughly 75 percent – in the predictive reliability of genetics on income. This reminded the team that environmental factors, such as parental influence and social contexts, still play a role in shaping socio-economic outcomes.
On top of that, differences in genetic associations across countries (and between genders) hinted that income-linked genetic factors aren’t exactly universal. Societal and cultural contexts still matter.
The ‘Income Factor’ and Socio-Economic Health Gradient
The researchers integrated results from the four different income measures to build what they called an “Income Factor,” a common genetic component linked to income-related traits. This factor worked closely with genetics to help determine educational attainment. But it also exposed distinct patterns tied to health outcomes.
Specifically, while higher educational attainment corresponded to better overall mental and physical health, the genetic components of income revealed a more complex relationship. For example, higher income synced up with better mental health but also riskier behaviors, such as drinking and smoking.
The study also demonstrated that 16 percent of the genetic variance in income appeared to be independent of educational attainment, highlighting income-specific genetic pathways. For example, the genetic components of income unrelated to education more strongly correlated with psychiatric disorders, such as schizophrenia and bipolar disorder.
The team also found a wide range of genetic associations that spanned different countries and genders. This, the authors insist, suggests that societal norms, labor market structures, and cultural values all play a huge part in shaping how genetic predispositions translate into income outcomes.
Debunking Genetic Determinism
The researchers are quick to caution against reading more into their findings – especially when it comes to genetic determinism. They point out that the labor market and society at large – by placing some skills and traits above others – steers the way our genes alter our incomes. As societal norms and economic conditions shift, the tie between genetics and socio-economic outcomes does, too.
Additionally, the study’s authors determined that only a quarter of the genetic effects they identified directly caused the outcomes. They found that environmental factors influenced the remaining 75 percent. This, they argue, reinforces the importance of social environments, educational opportunities, and public policy in swaying economic outcomes.
“Future research could focus on disentangling these relationships further by integrating genomic data with longitudinal assessments of environmental exposures and behavioural traits,” the authors conclude. “Such approaches could help elucidate the pathways through which genetic predispositions interact with socio-economic contexts, life experiences and individual behaviours to shape income-related outcomes. This line of research may ultimately contribute to a deeper understanding of the mechanisms underlying social mobility and economic inequality.”
Further Reading
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