Your Genes Matter More Than We Thought — A New Study Doubles the Estimated Role of Genetics in How Long You Live

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If you have been telling yourself that longevity is mostly a lifestyle game, this study from the Weizmann Institute of Science is going to complicate that story — in a way worth understanding.

For decades, the textbook number has been that about 20 percent of human lifespan is genetic. Uri Alon, a physicist-turned-systems biologist, always found that figure suspicious.

The original estimates came from studies of Scandinavian twins born between 1870 and 1900. During that era, extrinsic mortality (deaths from accidents, violence, and infections unrelated to the aging process itself) was high enough to drown out the genetic signal.

"At that time, people died of pneumonia and tuberculosis and not a lot of people made it to their 40s," Alon said. "In that situation, who cares how long your parents lived?"

In other words, genes never had a chance to show their hand.

His team examined a database of Swedish twins born later, between 1900 and 1935, and built a mathematical model to strip away extrinsic deaths. When they applied it to both the twin data and a database of centenarians' siblings, the heritability of lifespan roughly doubled — to about 50 percent.

The old studies were not wrong. They were measuring a different era, when medicine and sanitation had not yet cleared away the noise.

Nir Barzilai, director of the Institute for Aging Research at Albert Einstein College of Medicine, illustrated the point with his own family. His grandfather died of a heart attack at 68.

His father had one at the same age but survived thanks to triple bypass surgery and lived to 84. Same genes — different century.

Here is where this becomes personal for anyone building a longevity-focused lifestyle. If half the equation is genetic, does the other half still matter?

Every scientist interviewed said yes — emphatically. Thomas Perls, founding director of the New England Centenarian Study at Boston University, points to a 2018 study in Circulation showing that even without winning the genetic lottery, healthy behaviors can carry the average man to about 88 and the average woman to about 93.

Alon thinks of it as a "genetic set point." Healthy habits can add years on top of it.

But the asymmetry is important: bad habits do not merely subtract what good habits add. They can shear decades off a lifespan.

Morten Scheibye-Knudsen, an aging researcher at the University of Copenhagen, put the practical implication plainly. "You actually don't know your starting point — we have no way of measuring that."

His conclusion: "So that means you should not smoke, you should drink moderately and eat your vegetables."

At the extremes of old age — people living to 105 or 110 — genetics clearly dominate. But for the vast majority of us operating somewhere in the middle, the controllable half still represents an enormous range of outcomes.

For longevity science, the study carries a different kind of urgency. If hundreds of small genetic variations collectively account for half of lifespan, identifying them could unlock drug targets that influence the aging process itself.

This does not diminish the value of everything you are doing to live well — it contextualizes it. Your lifestyle choices are operating within a genetic range you did not choose, but that range is wide and where you land inside it is still substantially up to you.

The most useful reframe: you cannot out-exercise or out-supplement a genetic ceiling, but you can absolutely fall far short of your genetic potential through inaction. The controllable half is still worth every bit of effort.

Source: Cha, A.E. "Lifespan and Longevity: How Much Is Genetics?" The Washington Post, April 5, 2026.

Read the full article at The Washington Post

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