We were wrong about how much your genes shape your lifespan

Putting aside the risk of accidents or early illness, your genes may play a far greater role in lifespan than previously thought, according to a landmark study of twin data.

The recent analysis, led by researchers from the Weizmann Institute of Science, suggests that around 55 percent of the variation in human lifespans is influenced by genes—much higher than prior estimates of 20-25 percent, and in some studies as low as 6 percent.

“For many years, human lifespan was thought to be shaped almost entirely by non-genetic factors, which led to considerable skepticism about the role of genetics in aging and about the feasibility of identifying genetic determinants of longevity,” says molecular biologist Ben Shenhar of the Weizmann Institute of Science.

Researchers distinguish between intrinsic and extrinsic causes of death. Intrinsic deaths are driven by internal factors such as aging and genetics, while extrinsic deaths include accidents, infections, and other external events.

Historical studies often lacked detailed cause-of-death data, making it difficult to separate these factors. 

This study analyzed thousands of twins, including siblings raised apart—a group previously overlooked—allowing researchers to isolate the influence of genes from post-birth factors like lifestyle, diet, and education.

Mathematical models were used to filter out extrinsic causes, suggesting deaths are more likely to be intrinsic as people age. “Such high heritability is similar to that of most other complex human traits and to life-span heritability in other species,” the researchers write in Science (2026).

While these findings do not contradict earlier studies, they suggest prior datasets underestimated the genetic contribution to lifespan. The team now plans to test their conclusions against modern datasets and explore which gene variants have the most influence.

“If heritability is high, as we have shown, this creates an incentive to search for gene variants that extend lifespan, in order to understand the biology of aging and, potentially, to address it therapeutically,” Shenhar adds.