For many years, scientists believed that genetics only played a small role in determining a person’s lifespan. Most of the variation in how long people lived was attributed to environment, lifestyle, and chance. Earlier estimates suggested that inherited factors accounted for about 20-25% of differences in human lifespan, with some large-scale studies reporting numbers below 10%.
A recent study from the Weizmann Institute of Science, published in Science, challenges these earlier views. The researchers found that genetics may account for about half of the variation in human lifespan, which is at least twice previous estimates and, in some cases, much higher. The study was led by Ben Shenhar from the lab of Prof. Uri Alon in Weizmann’s Molecular Cell Biology Department.
The Problem With Earlier Estimates
The researchers identified a key limitation in older datasets: they could not account for extrinsic mortality, which refers to deaths from accidents, infectious diseases, and environmental hazards unrelated to aging.
Older twin registries, which have been the main resource for studying heritability, did not include detailed information about causes of death. As a result, it was not possible to distinguish between deaths related to genetic aging and those caused by external factors. When a significant number of deaths in a dataset are due to infections or accidents, the genetic influence on aging becomes harder to detect, and heritability estimates decrease.
This issue was particularly significant in historical datasets. Shenhar explained that extrinsic mortality was about ten times higher when the twins in these studies were alive, before antibiotics were widely available. Most of these deaths were caused by infectious diseases that are now treatable.
A New Analytical Framework
The researchers created a mathematical framework to filter out deaths from external causes to address this. They also used simulations of virtual twins to model how heritability would appear if they considered only deaths related to biological aging.
The team then tested their predictions using more recent data. They examined three large twin registries from Sweden and Denmark and, for the first time in this field, included information from twins raised in different households. Identical twins share the same DNA regardless of where they grow up, making twins raised in separate households a particularly powerful tool for separating genetic influence from environmental ones. The analysis showed that as deaths from external causes decrease in newer datasets, the measured heritability of lifespan increases. The new estimate of about 50% heritability for human lifespan is similar to findings for other complex human traits and consistent with results from animal studies.
What the Numbers Mean
The implications depend on the specific cause of death. According to the researchers, up to age 80, the heritability of dying from dementia is about 70%, which is much higher than the heritability for deaths from cancer or heart disease.
“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,” said Shenhar. “By contrast, 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.”
The findings do not diminish the importance of lifestyle, environment, or chance in determining an individual’s lifespan. Researchers note that these factors remain significant and that many variables, including randomness, influence lifespan. However, the study suggests that genetic research into aging should be a higher priority. If earlier studies underestimated the genetic contribution to lifespan because of a flaw in their design, there is now an opportunity to search more effectively for the specific genes involved. That search, the researchers argue, now has a stronger scientific foundation.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.