Some people who reach old age attribute it to healthy eating, others to their ability to avoid trouble, and still others to good genetics.
Now researchers say they’ve found a key reason for longevity: genetics. New findings show genetics account for more than 50 percent of the variation in lifespan.
A team of researchers from the Weizmann Institute of Science in Israel said previous studies trying to identify the genetic component of longevity did not account for “external mortality.” This refers to lives cut short by accidents, homicide, infectious disease, or other external causes. External mortality increases with age as people become more vulnerable.
The scientists say this masking effect hid the genetic contribution to human lifespan. In their study, the team focused on examining “heritability”—the proportion of variation in traits that is genetic rather than environmental, such as height, body mass, or other traits.
What Did the Scientists Discover?
Previous studies on human lifespan showed a wide range of heritability values, from 6 to 33 percent. However, the researchers say those figures were underestimated, as reported by The Guardian.
“I hope this inspires researchers to delve deeper into that influence on lifespan. These genes will tell us about the mechanisms that govern our internal clock. In the future, they could be used in therapies that slow down the aging process, thereby delaying the onset of all age-related diseases simultaneously,” said Professor Uri Alon, the senior author of the study.
The scientists developed a mathematical model that accounts for external mortality and the impact of biological aging, and calibrated it using correlations of lifespan from historical datasets of thousands of twin pairs from Denmark and Sweden.
To detect signals from biological aging driven by genetic factors, the team excluded the influence of external mortality. The results, published in the journal Science, confirmed that 50–55 percent of the variation in human lifespan is attributable to genetics. The researchers say this figure is comparable to heritability values observed in wild mice under laboratory conditions.
The researchers say the remaining variation in human lifespan can likely be explained by random biological effects and environmental influences.
“This is where we expect to find lifestyle factors—diet, exercise, social relationships, environmental exposures, and more,” said Ben Shenhar, the lead author of the study. He added that the impact of lifestyle and the environment becomes increasingly significant with age.
The research team also validated their findings using data from an American sibling study. In that dataset, the heritability of lifespan was also over 50 percent.
Meanwhile, an analysis of another Swedish dataset showed that as external mortality decreased since the early 20th century—likely because of public-health improvements—the predicted genetic contribution to lifespan increased. This supports the idea that external mortality is a key factor. The team also found that heritability of lifespan varies depending on the cause of death, such as cancer and dementia.
Ben Shenhar pointed to everyday experience as evidence of genetics’ role in longevity. “For instance, about 20 percent of centenarians reach 100 without any serious debilitating diseases, which may indicate a protective effect of their genes. Many of these genes have already been identified by researchers, but there is still much to discover,” he said.
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