In what might be the most compelling scientific case yet for casting a wide net in your dating life, researchers have discovered that children of genetically diverse parents are measurably taller, smarter, and achieve higher levels of education than those whose parents are more closely related.
This isn’t just a minor effect—the landmark study found that kids born to first cousins end up, on average, 1.2 centimeters shorter and receive 10 months less education than their peers from more genetically diverse backgrounds.
These findings come from one of the most comprehensive studies ever conducted on genetic diversity, analyzing data from 110 genetic studies encompassing 350,000 individuals across four continents—Africa, Asia, Europe, and North America.
The research provides concrete evidence for something many suspected but couldn’t prove: that increasing genetic diversity doesn’t just prevent negative outcomes, it actively promotes positive ones.
“Most people would believe a diverse gene-pool is a good thing, but the discovery that height is associated with diversity wouldn’t have been foreseen,” explained Nathan Richardson from the UK Medical Research Council, one of the researchers involved in the groundbreaking study.
The Science Behind the Discovery
For centuries, we’ve understood that closely related parents increase their children’s risk of genetic disorders.
From Habsburg royalty’s notorious “Habsburg jaw” to higher rates of rare diseases in isolated communities, the evidence against close-relation breeding has been overwhelming.
However, scientists weren’t sure if the inverse relationship held true—whether greater genetic distance between parents conferred measurable advantages.
To answer this question definitively, British researchers examined the genetic information of 354,224 individuals from 102 cohorts spanning Africa, Asia, Europe, and North America.
They specifically looked for patterns of homozygosity—instances where a child inherits identical copies of specific genes from both parents.
Homozygosity, a common result of relatives having children together, serves as a reliable marker for how closely related a person’s parents are.
The higher the homozygosity, the more closely related the parents likely were.
By calculating this value for hundreds of thousands of people, the researchers created a powerful dataset to test against various health and cognitive metrics.
The team compared these homozygosity values against 16 traits of public health importance, including height, lung capacity, blood pressure, cholesterol levels, and various measures of cognitive ability.
What they discovered was both surprising and significant.
Four Key Traits Linked to Genetic Diversity
Of the 16 traits examined, four showed clear correlations with genetic diversity:
- Height – Greater genetic diversity was associated with increased height
- Lung capacity – More diverse genetics led to improved lung function
- Cognitive ability – Higher genetic diversity correlated with better cognitive performance
- Educational attainment – Children of more genetically diverse parents completed more years of education
The effects were substantial enough to be statistically significant even when controlling for other factors.
For instance, children born to first cousins—a relatively close genetic relationship—averaged 1.2 centimeters shorter than their peers from more genetically diverse parents.
They also received approximately 10 months less education on average.
The Evolutionary Paradox You Didn’t Expect
Here’s where conventional wisdom about genetics gets turned on its head: Many people assume that the benefits of genetic diversity mainly involve avoiding rare genetic diseases.
But this study reveals something much more profound—genetic diversity appears to be actively enhancing traits that have traditionally been considered advantageous from an evolutionary perspective.
This challenges the simplistic view that genetic diversity merely prevents bad outcomes.
Instead, it suggests that mixing genetic backgrounds actively promotes positive developmental traits that extend well beyond basic health measures.
What’s particularly surprising is that the researchers found no correlation between genetic diversity and cardio-metabolic factors like cholesterol levels or blood pressure.
“Inbreeding does not affect the cardio-metabolic factors that lead to the diseases that many of us die from,” explained Jim Wilson from the University of Edinburgh, one of the study’s authors.
This unexpected finding contradicts the assumption that genetic diversity would broadly improve all health metrics.
Instead, its benefits appear concentrated in specific developmental areas—height, lung function, and cognitive capabilities—rather than affecting disease risk factors that many public health experts might have expected to see improved.
Could This Explain Why Each Generation Is Getting Taller and Smarter?
One of the most intriguing implications of this research is its potential to explain two well-documented phenomena: the steady increase in average height and the rising IQ scores (known as the Flynn Effect) observed across generations throughout the 20th century.
While improved nutrition, healthcare, and education have long been considered the primary drivers of these generational improvements, this new research suggests that increasing genetic diversity could be playing a supporting role.
As transportation improved and communities became less isolated over the past century, people began marrying partners from more diverse geographic and genetic backgrounds.
“These results could also go some way to explaining the ‘Flynn Effect’—the increase in intelligence from one generation to the next first documented in the 20th century,” Philip Oldfield noted in The Guardian’s coverage of the study.
While the researchers acknowledge that socio-economic factors such as increased schooling and better nutrition remain the primary drivers of generational improvements, genetic diversity may contribute more than previously thought.
As one researcher put it: “The increases in intelligence [from the Flynn Effect] are too big to be explained by our results alone, but they might be a contributor.”
What This Means for Public Health and Future Generations
The implications of this research extend far beyond interesting scientific trivia.
Understanding how genetic diversity affects human development could inform public health policies, especially in communities with historically limited genetic exchange.
In smaller, isolated communities—whether geographic, religious, or cultural—awareness of the benefits of genetic diversity could help reduce rates of close-relation marriages and the associated developmental disadvantages.
However, the researchers emphasize that the cardio-metabolic traits unaffected by genetic diversity offer some reassurance for such communities.
“Inbreeding does not affect the cardio-metabolic factors that lead to the diseases that many of us die from,” Jim Wilson from the University of Edinburgh told New Scientist.
This suggests that while isolated populations might face certain developmental disadvantages, they aren’t necessarily at higher risk for heart disease, diabetes, or other major killers.
Nature, Nurture, or Both?
While the study provides compelling evidence linking genetic diversity to improved physical and cognitive traits, the researchers caution against oversimplification.
Many of the traits studied—particularly cognitive ability and educational attainment—are influenced by a complex interplay of genetic and environmental factors.
“We still need to figure out how much of a trait is down to factors other than genetics,” emphasized one of the researchers.
“For example, cognition depends on a lot of environmental factors too.”
This nuance is crucial for interpreting the findings.
While genetic diversity appears to confer certain advantages, these advantages exist within broader social, economic, and cultural contexts that can enhance or diminish their effects.
A child with genetically diverse parents who lacks access to quality education, for instance, may not fully realize the cognitive potential their genetic background might offer.
Diversity Across Continents
One of the study’s most remarkable features is its global scope.
By analyzing data from individuals across Africa, Asia, Europe, and North America, the researchers were able to observe how genetic diversity affects human development across different populations and environmental conditions.
This cross-continental approach strengthens the findings by demonstrating that the benefits of genetic diversity aren’t limited to specific populations or environments.
Rather, they appear to be fundamental biological principles that apply across human societies.
The global nature of the study also allows researchers to control for the confounding effects of different environments.
When similar patterns emerge across diverse populations living in vastly different conditions, it provides stronger evidence that the observed effects are genuinely linked to genetics rather than environmental factors.
Next Steps in Understanding Our Genetic Heritage
Publishing their findings in the prestigious journal Nature, the research team outlined an ambitious next phase for their work: identifying specific parts of the genome that most benefit from increased diversity.
This next step could revolutionize our understanding of human genetics by pinpointing precisely which genes and genetic regions contribute most significantly to the advantages conferred by genetic diversity.
Such knowledge could potentially lead to more targeted genetic counseling and perhaps even inform future genetic therapies.
“We’re just beginning to understand the complex ways genetic diversity shapes human development,” explained one researcher.
“The next phase will involve mapping exactly which parts of our genome respond most strongly to diverse genetic inputs.”
What This Means for You
For the average person, this research offers fascinating insights into how our ancestral backgrounds shape our development.
While individual outcomes always involve countless factors beyond genetics, understanding the potential benefits of genetic diversity adds another piece to the puzzle of human development.
It also serves as a compelling reminder of humanity’s shared heritage and the biological benefits of cross-cultural connections.
As our world grows increasingly interconnected, the mixing of previously separate genetic lineages may contribute to continued improvements in human height, lung function, and cognitive capabilities—a subtle but measurable benefit of our globalizing world.
The study represents not just a significant advance in genetic research, but a window into the biological foundations of human diversity—and a scientific testament to the notion that, at least at the genetic level, variety truly is the spice of life.
