The World's Oldest Tortoise May Hold the Secret to Longevity

Meet Jonathan, the world's oldest tortoise — a giant tortoise hatched around 1832 in the Seychelles who has been lumbering around St. Helena, a remote South Atlantic island, since 1882. At roughly 194 years old, he has outlived everyone who ever met him. Now, according to a study published October 7 in Science Advances, his DNA may hold the secret to a long, healthy life.

An international team led by neurologist Wes Clark of the Nashville-based Kallel Foundation spent years piecing together Jonathan's genome and epigenome — the chemical marks that switch genes on and off. For the world's oldest tortoise, the team made the widest age-gap methylation comparison ever attempted: Jonathan's epigenome measured against four other Aldabra tortoises, from juveniles to older adults, spanning nearly two centuries of life.

What they found was striking. Promoters — the on/off switches of genes — involved in mitochondrial function and RNA processing showed "low methylation entropy": remarkably orderly chemical marks, nearly as pristine as those of a five-year-old juvenile tortoise. In plain language, while most animals' genetic switches get noisy and disordered with age, Jonathan's key energy-production genes stayed crisply legible, keeping his cells' mitochondria humming. The researchers concluded this "high-fidelity gene expression" partially protected him from age-related decline, as reported by MedicalXpress.

The genes behind the marathon

The team also catalogued 287 genes with variants unique to the world's oldest tortoise, of which 41 were judged functionally significant — including genes linked to tumor suppression, DNA repair, telomere maintenance, and autophagy, the cell's recycling system. He also carries extra copies of a gene encoding a protein that targets aging and cancerous cells, according to the study. First author Benjamin Vaisvil offered an analogy for the finding: the genome is a cookbook and the epigenome its margin notes; with age, the notes get hard to read, but Jonathan's notes in the key regions stayed legible.

The results echo a 2025 study by Manel Esteller's team in Barcelona, which found exceptionally efficient mitochondrial function in a 117-year-old woman. Esteller, who was not involved in the tortoise work, said "exceptions" like Jonathan can teach us the global mechanisms of aging. Clark's own entry point to the research was a cancer puzzle: as a neuro-oncologist, he had wondered why brain-tumor incidence climbs until the mid-80s and then stops — as if the extremely old are somehow protected.

Why the world's oldest tortoise matters — and what it doesn't prove

The world's oldest tortoise won't hand you a longevity pill, and the researchers are upfront about the limits. St. Helena authorities refused a blood draw because of infection risk, so the team worked from saliva swabs — fragmentary DNA prone to bacterial contamination, with gaps filled using another tortoise's genome. The comparison group was just four other tortoises, and as Osaka University's Kousuke Hashimoto noted, that is a small window. One very old animal is still one data point: the finding shows association, not a proven mechanism.

But the study of the world's oldest tortoise is also a proof of concept for a bigger idea — that the aging clock may be readable, and perhaps tunable, in the epigenome rather than the genome. Methylation has been the basis of "biological age" tests for a decade, but Jonathan's case shows the pattern at an extreme no human sample can reach: switches in the most critical pathways can stay youthful across centuries. That makes the humble tortoise a reference point for what successful aging looks like at the molecular level.

The Kallel Foundation hopes to push past the commercial bottleneck: drugs like rapamycin show anti-aging potential but are off-patent, so pharmaceutical companies won't fund the trials. As a nonprofit, Clark said, the foundation wants to run "clinical trials that no drug company wants to do" — potentially starting next year, as reported by Vanderbilt University Medical Center.

For the world's oldest tortoise, who predates the telephone, the lesson is quietly radical: aging may be less about the genes you're dealt and more about how clearly your cells can still read them. Jonathan's margin notes are still legible after 194 years — and science is finally learning to read over his very slow shoulder.

Related reading: how your genes could predict hearing loss before it starts and the Nobel Chemistry prize for mirror-molecule research.