Weizmann study finds genes explain about half of human lifespan, double past estimates

How much of a long life is written in our genes? For years the standard answer was: not much. Twin studies put the heritability of lifespan at roughly 20 to 25 percent, and some recent large analyses found less than 10 percent. A study published in Science on 29 January 2026 by physicist Ben Shenhar and systems biologist Uri Alon of the Weizmann Institute of Science argues that those figures were badly distorted, and that genetics accounts for about half of the variation in human lifespan.

The key, the researchers say, is what they call extrinsic mortality: deaths caused by things outside the body, such as accidents, violence and infectious disease. The classic twin datasets from Sweden and Denmark followed people born largely in the 19th century, when such deaths were around ten times more common than today, and the records gave age at death but not its cause. That external 'noise' swamped the genetic signal. Using mathematical models, three large twin databases including a set of twins raised apart, and simulations of 'virtual twins', the team separated deaths due to biological ageing from those due to outside causes. Heritability rose as extrinsic mortality fell.

With that correction, lifespan looks about as heritable as other complex human traits, and in line with results from laboratory animals. The analysis also suggested that, up to age 80, the risk of dying from dementia is roughly 70 percent heritable, higher than for cancer or heart disease. Longevity is likely shaped by hundreds or thousands of genes, some harmful and some protective, which may help explain why certain families produce many centenarians.

The authors say the low earlier estimates may have discouraged investment in the genetics of ageing, and that their result gives new reason to search for gene variants that extend healthy life.