If My Parents Lived Long, So Would I?: The Truth About Lifespan

Correlation between genes and lifespan
A completely different result was obtained

“My parents lived a long life, so I will live a long time too.” It’s a story everyone has told at least once. But how scientifically accurate is this belief?

Over the past few decades, the scientific community has determined that genes determine only about 20-25% of lifespan. The established theory was that the remaining 75% was down to lifestyle habits and environment.

However, a study published in the international academic journal ‘Science’ earlier this month turned this conventional wisdom on its head. A research team at Israel’s Weizmann Institute published analysis results showing that genes explain 50-55% of variation in lifespan.

The research team analyzed the siblings of a Scandinavian twin cohort (including separated twins) and American centenarians. The key was classification of cause of death.

The researchers removed ‘extrinsic deaths’ such as accidents and infections and separately calculated ‘intrinsic deaths’ due to aging and chronic diseases. The results were surprising. When extrinsic causes were excluded, the contribution of genes jumped to more than double the previous estimate.

This discovery goes beyond simple numerical changes and has important implications for modern people’s longevity strategies.

The landscape of death has changed from 100 years ago.

The reason for the change in estimates is historical changes in causes of death. Until the 1920s, most people lost their lives due to infectious diseases, malnutrition, and accidents.

At that time, no matter how good genes you were born with, you were helpless in the face of tuberculosis bacteria or traffic accidents. It was a time when environmental factors were overwhelming.

However, as of 2026, the situation has completely changed in developed countries. Vaccine distribution has expanded, and nutritional conditions have improved incomparably compared to the past. Air pollution has also decreased significantly.

Nowadays, most people end their lives due to age-related diseases such as dementia, heart disease, and cancer. According to the research team’s analysis, genes account for most of the variation in dementia, have a moderate impact in heart disease, and have a relatively low impact in cancer.

As external threats disappear, genetic differences become more clearly revealed. The research team explains that past studies underestimated the true influence of genes because they used population data from the 18th and 19th centuries.

As the environment improved, genes became more prominent.

There is something you should not misunderstand here. It’s not that genes suddenly became more powerful. Epidemiology experts at Karolinska Institutet emphasized, “The environment has changed, not the DNA.”

It is easy to understand using height growth as an example. 100 years ago, even people who were genetically tall could not grow properly due to lack of nutrition.

Environmental variables were dominant. But now, with most people getting enough nutrition, height differences are almost entirely explained by genes.

The same goes for lifespan. As vaccines, clean water, and nutritious food become more common, environmental fluctuations have decreased. Lifespan researchers call this an increase in ‘heritability’.

What is important is that this number is not a fixed biological property, but a relative indicator that varies depending on population groups and times.

20-25% was the past figure when there were many external threats, and 50-55% is the current figure when most of those threats have been eliminated. It is simply the result of measuring the same characteristics in a different environment.

The power of lifestyle habits remains the same

So what does this research result that genes account for half mean to us?

“If it is proven to be highly heritable, it will motivate us to look for life-extending genes and open up the possibility of therapeutically addressing the biology of aging,” said Dr. Ben Schenhar of the Weizmann Institute of Science.

However, epidemiology experts call for cautious interpretation. This is because the headline “50% heritable” may be misunderstood as if individual efforts are meaningless.

The researchers also stated that “the other half still depends on environment, lifestyle, medical care, and random biological processes.”

He also explained, “People with strong genes can live long lives even in harsh environments, and people with unfavorable genes can fully compensate with good nutrition, exercise, and medical care.”

Ultimately, the message this study sends is clear. Genes are important, but they are not destiny.

As the environment has improved, genetic differences have become more visible, but the value of healthy eating habits, regular exercise, and regular checkups has not diminished one bit.

Rather, now that external threats have disappeared, the impact of individual choices on lifespan is more direct and certain than ever. The path to longevity is still in our hands.