A 194-Year-Old Tortoise Defies Every Rule of Aging

He was alive when Charles Darwin was still developing his theory of evolution. He shared his birth year with Lewis Carroll and Gustave Eiffel. And today, at roughly 194 years old, a giant tortoise named Jonathan is not only still alive — he’s giving scientists one of their most extraordinary windows yet into the biology of aging. A study published in the journal Science Advances has pinpointed 287 unique gene variants in this remarkably old giant tortoise that reduce the usual effects of aging.

Jonathan lives on the remote south Atlantic island of St. Helena, and at 194 years old, he has outlasted the expected lifespan for an Aldabra giant tortoise by about a century. That alone would be remarkable. But what researchers found when they examined his DNA is what’s truly turning heads in the scientific community.

What’s Actually Inside His DNA

Scientists pinpointed 287 unique gene variants in Jonathan that reduce the usual effects of aging, controlling key processes in the body — including repairing DNA damage, reducing inflammation, regulating insulin, and suppressing cancer. To collect this data, researchers traveled to the island and swabbed Jonathan’s saliva, then sequenced the samples back in the United States.

The research zoomed in on Jonathan’s genes as well as the chemical tags that sit on top of DNA molecules, known as epigenetic markers, which help control which genes are activated and to what degree. The analysis found that Jonathan’s genes associated with mitochondrial function are in great shape epigenetically, suggesting they’ve played a big role in the tortoise’s extraordinary longevity.

Perhaps the most striking discovery was how little Jonathan’s genetic machinery has deteriorated. When the team compared Jonathan’s epigenome — the “on/off” switches on his genes — with those of younger giant tortoises of the same species, they found the switches controlling his DNA repair and metabolism genes were very similar to those in his younger relatives. Usually, the epigenome changes over time, contributing to the aging process, and this is a key reason why things start to go wrong in older bodies. In Jonathan, that deterioration appears to have been dramatically slowed.

What This Means for Human Health

Jonathan’s gene regulation is very similar to that of a very young animal — meaning he’s not only a bit more resistant to the symptoms of aging, he’s actually genuinely aging more slowly than scientists would expect. That distinction matters enormously. Resistance to aging symptoms is one thing; a fundamentally slower biological clock is another.

Aided by an international team including UCLA’s Steve Horvath, known for developing a methylation-based aging “clock,” researchers determined that promoters involved in mitochondrial function and RNA processing had “low methylation entropy” — a finding that mirrors a 2025 study showing “exceptionally efficient mitochondrial function” in a 117-year-old woman. The parallel between the world’s oldest tortoise and one of the world’s oldest humans is difficult to ignore.

This study marks the first time the epigenome of a giant tortoise has been investigated, and it was led by researchers at longevity research nonprofit Kallel, who say that cracking the genetic code of a multi-century life offers unprecedented insights into extreme longevity. Beyond genetics, experts note that Jonathan’s plant-heavy diet, stable tropical climate, and dedicated veterinary care have also contributed to his remarkable condition.

The Road Ahead

Additional studies using blood, which yields a more complete and “pristine” DNA sequence, will be needed to validate Jonathan’s findings. The Kallel Foundation also plans to expand its investigations into other long-lived species and other pathways associated with aging.

For now, Jonathan grazes on St. Helena, blissfully unaware that his saliva may one day inform therapies that extend human life. The tortoise who outlived empires, world wars, and countless scientific revolutions may yet have one more gift to offer — a biological blueprint for aging well. Science has spent centuries watching him. Now, finally, it’s beginning to understand him.