Recent research suggests that genes may dictate how long humans live to a greater extent than previously understood. A new analysis indicates that genetics account for roughly half of the factors determining lifespan when deaths from external causes like accidents or diseases are removed from the equation. This challenges the long-held assumption that lifestyle and environmental factors are the primary determinants of longevity.
Rethinking Heritability
For years, estimates of genetic influence on lifespan have hovered around 20-25%, with some studies suggesting even lower percentages. This led to skepticism about the value of genetic research in aging, reinforcing the idea that external factors dominate lifespan. However, biophysicist Ben Shenhar and his team at the Weizmann Institute of Science discovered a critical shift in their modeling: eliminating accidental or environmental deaths dramatically increased the calculated genetic component of lifespan.
Methodology and Data
The researchers didn’t initially set out to study heritability. They were modeling how aging varies across populations when Shenhar noticed the effect of removing extrinsic mortality. The team then compiled mortality data from Sweden, Denmark, and the U.S., alongside twin and centenarian sibling studies. Since historical data often lacks precise cause-of-death information, they used mathematical modeling to estimate and isolate the impact of external factors. By identifying a mortality plateau between ages 20-40—a period of reduced accidental deaths—they calculated heritability both with and without those external influences.
The Results: A 55% Genetic Influence
The findings were striking. When the team factored out extrinsic mortality, the heritability of lifespan consistently reached approximately 55%, more than double many previous estimates. This brings human lifespan into line with the heritability of other physiological traits, which typically fall around 50%. The implications are profound: if humans were raised in perfectly controlled environments, genetics would explain more than half of their longevity.
Implications for Future Research
This new understanding also aligns with genetic studies of lifespan in animals like mice and flies. Biostatistician Paola Sebastiani, who was not involved in the research, notes that the findings resemble her own work on extreme longevity (living past 100). Going forward, focusing on genetic factors while minimizing external death-related variables could accelerate discoveries in aging research. Shenhar’s team is now shifting its focus to the remaining environmental contributions, questioning how much is due to random chance versus lifestyle choices.
These findings represent a significant shift, suggesting that genetics play a more central role in determining lifespan than previously believed.
