One of the most common questions people ask older adults is, “How did you live such a long, healthy life?” The answers are usually all over the map. Some swear by early morning sunlight. Others credit a lifetime of avoiding junk food. A few shrug and say they never did anything special, they just tried to enjoy the small moments as they came.
Today, that same curiosity has helped fuel a booming wellness industry. From moving your entire family to Blue Zones to booking sessions in hyperbaric oxygen chambers that promise more energy and “reversed” aging, there’s no shortage of strategies claiming to extend your lifespan. But new research suggests we may have been underestimating one major factor all along: genetics.
A study published in Science analyzed historical data from thousands of twin pairs in Denmark and Sweden and found that genetics may account for as much as 55 percent of how long we’re likely to live. That figure is dramatically higher than earlier estimates, which placed the genetic contribution anywhere from 6 to 33 percent.
“The key insight is that extrinsic mortality systematically masked the genetic contribution to life span in traditional analyses,” the study authors wrote.
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The researchers note that earlier studies relied heavily on data from people born before the 19th century, when infectious diseases, accidents, and poor sanitation claimed far more lives. Before modern medicine, hygiene, and safety standards, many people simply didn’t live long enough for genetic factors tied to aging to fully show up.
Once those external causes of early death were accounted for, the picture changed. The authors found that roughly half of the variation in human lifespan could be explained by genetics, a number they say is comparable to what’s been observed in laboratory studies of wild mice. The remaining variation appears to come from environmental influences and random biological factors.
“Identifying the genetic variants underlying this heritability would help us to understand the fundamental mechanisms of human aging,” the authors said.
None of this means lifestyle suddenly stops mattering, though. Genetics may shape the ceiling, but how you eat, move, sleep, and manage stress still determines how well you live within it. So no, this isn’t a free pass to abandon healthy habits. Your genes may have more influence than we once thought, but what you do with them still counts.
This story was originally published by Men’s Journal on Jan 30, 2026, where it first appeared in the Health & Fitness section. Add Men’s Journal as a Preferred Source by clicking here.