Scientists have long debated how much our DNA influences our final age. For decades, the standard estimate suggested that genes only accounted for 25% of lifespan variation. However, a groundbreaking study published in Science suggests that genetics actually account for over 50% of lifespan variation.
Researchers explain that older studies often failed to account for changing causes of death. A century ago, many people died from what experts call extrinsic causes, such as infections or accidents. Today, most deaths in developed nations stem from intrinsic causes, meaning the body gradually wears out over time.
The Power of Twin Studies
To find these answers, the research team analyzed large groups of Scandinavian twins. They specifically excluded deaths from external factors to get a clearer picture of aging. By stripping away accidents and infections, the estimated genetic contribution jumped from 25% to nearly 55%.
Why the Percentage Is Rising
Our genes have not actually become more powerful over the last century. Instead, our environments have become more favourable through better medicine and nutrition. Because environmental differences have narrowed, the remaining variation in lifespan is now more likely to be genetic.
The Height Comparison
Think about human height as a perfect example of this biological concept. In the past, height depended mostly on whether a child had enough food to grow. Today, because most people receive adequate nutrition, your height is primarily determined by your parents’ DNA.
The Role of Specific Diseases
The study notes that genetic influence varies significantly depending on the specific disease. For instance, genetics explain a large portion of dementia risk but play a smaller role in cancer. Heart disease falls somewhere in the middle of this genetic spectrum.
Does Lifestyle Still Matter?
Even with a higher genetic influence, lifestyle choices remain critical for your health. While genetics may set your potential lifespan, a poor environment can still prevent you from reaching it. We have reduced the impact of environmental threats, which naturally makes our DNA appear more prominent.
The Changing Face of Heritability
Recent data indicates that the genetic contribution to your lifespan might actually be between 50% and 55%. This shift occurs because heritability is not a fixed biological property of your DNA. Instead, it is a measure that depends entirely on the specific population and the circumstances being studied.
Historical populations faced constant external threats, such as dangerous infections, poor nutrition, and accidental deaths . These external factors dominated the data, making the influence of genetics appear much smaller than it actually was.
A New Era of Aging
In modern wealthy nations, many of these external threats have been reduced or entirely eliminated . Consequently, most deaths now result from intrinsic causes, such as the body naturally wearing out over time. As our environments become more favourable, the genetic component of aging naturally appears much larger in statistical models.
However, this does not mean that your genes have suddenly become more powerful than before . It simply means that because we have narrowed the environmental differences, the remaining variation is explained by DNA. Notably, this is similar to how genetics now primarily determine height in well-nourished populations.
Personalized Paths to Longevity
The headline figure of “50% heritability” can be easily misunderstood by the general public. It does not mean that genes determine exactly half of every single person’s individual life chances. In reality, the genetic contribution for any given person can range from very small to very large.
Furthermore, there are many different routes you can take to achieve a long and healthy life.
Some individuals possess robust genetic profiles that protect them even when living in difficult or harsh conditions . Other people successfully compensate for less favourable genetics through excellent nutrition, regular exercise, and modern healthcare.
Why Environment Still Matters
Despite the higher genetic estimates, experts admit that half of lifespan variation still depends on your lifestyle. Factors such as healthcare access and random biological processes, like cancer, still play a massive role. Understanding how genetic factors interact with different environments is likely the key to explaining human longevity.
Ultimately, both your genes and your environment matter, and they matter most when they work together. You will probably never receive a simple answer regarding how much of your lifespan is determined by genes alone.
Q&A Section
Q: Did our genes become more powerful over the last century?
No, our DNA remains the same, but our environment has improved significantly.
Q: Why was the old estimate of 25% so much lower?
Previous studies included deaths from accidents and infections, which are not related to biological aging.
Q: Does this mean I cannot influence how long I live?
You can still influence your lifespan because environment and lifestyle still account for nearly half of the variation.
FAQ
What is the difference between extrinsic and intrinsic causes of death?
Extrinsic causes include external threats like accidents or infections, while intrinsic causes relate to the body wearing out.
How did the researchers conduct this study?
The team studied Scandinavian twins, twins raised apart, and siblings of centenarians to isolate genetic factors from environmental ones.
What is “heritability” in scientific terms?
Heritability is the proportion of variation in a trait, like lifespan, that is attributed to genetic differences.
Which diseases are most influenced by genetics according to the study?
Dementia shows a very high genetic link, while cancer shows a relatively modest genetic influence compared to other conditions.
