Jonathan, the giant tortoise believed to be 194 years old, carries gene switches that look strikingly young for an animal born around 1832, according to a study published Oct. 7 in Science Advances. The researchers report that switches controlling genes tied to energy production in Jonathan's cells resemble those of a 5-year-old tortoise, and that he carries 287 unique gene variants linked to DNA repair, inflammation, insulin regulation and cancer suppression, according to a University of Cambridge release.

The limitations matter as much as the headline. The work rests on one animal — a single, famous tortoise — cheek samples rather than blood and comparisons with only a handful of other tortoises. The authors did not show that these genetic traits caused Jonathan's long life.

The study is the first look at the epigenome of a giant tortoise, the chemical on-off switches that control which genes are active. For conservation scientists, it is also a reminder that giant tortoises are among the last survivors of large animals that once dominated many of the world's islands, and that their biology is still poorly understood.

A Two-Century Genome From a Cheek Scrape

Getting Jonathan's DNA was not simple. Island authorities on St Helena, the British Overseas Territory in the South Atlantic where he lives, would not allow his veterinarian to draw blood because of infection risk, Live Science reported. The first cheek swabs yielded DNA from mouth bacteria instead of the tortoise, so the team had to request a second round of cheek scrapes.

Because that DNA was fragmented, researchers filled gaps using a reference genome from a 36-year-old Aldabra giant tortoise named Tank. They also compared Jonathan's genes with those of Lonesome George, the Galápagos tortoise believed to be over 100 when he died in 2012. Against those two animals, Jonathan carried 287 unique variants in genes previously linked to aging pathways, including telomere maintenance.

Young-Looking Switches in an Old Body

The team then compared DNA methylation, a type of chemical tag on DNA, between Jonathan and four other Aldabra tortoises ranging from a 5-year-old to two 91-year-olds. Over time these tags usually become more disordered, a pattern scientists call methylation entropy, and that drift is linked to aging.

For most genes, Jonathan's patterns were more disordered than those of young tortoises, as expected for his age. But in a set of genes tied to mitochondria, the energy-producing parts of cells, the switches were unusually orderly. Senior author Stephen Clark told IFLScience that Jonathan "has some gene promoters that look very young," adding that the same promoters looked old in the two 91-year-olds.

Justin Gerlach of Peterhouse at the University of Cambridge, a co-author who has studied giant tortoise ecology and conservation for decades, said in the release that "gene regulators involved in energy production and DNA repair have remained incredibly stable" across Jonathan's long life.

Independent Scientists Urge Caution

Researchers not involved in the work welcomed the data but warned against overreading it. Vincent Lynch, a biology professor at the University at Buffalo, told Live Science that Jonathan's full genetic profile cannot be known until tissues can be sampled after his death, and he questioned whether entropy is the best way to describe age-related methylation. "Maybe Jonathan is just really good at being old," he said.

Greer Dolby, an assistant biology professor at the University of Alabama at Birmingham, told Live Science the flagged pathways overlap with those involved in human aging. More experiments are needed to learn whether the mitochondrial pattern appears in other long-lived Aldabra tortoises or is unique to Jonathan.

Readers should also know who is behind the work. The study was led by Kallel, a Nashville-based longevity nonprofit whose founder, Clark, said its goal is to turn such insights into affordable treatments for people, and the research was funded by the Voland Fund. Neither connection changes the data, but the findings come from a single observational case study and do not justify any longevity product or supplement claim. Be skeptical of marketing that cites Jonathan.

The findings are published in Science Advances. The study shows an association between young-looking gene switches and an exceptionally old animal. It does not show cause and effect, and it says nothing yet about how other tortoises, or people, age.

Island Survivors with More to Teach

Jonathan arrived on St Helena from the Seychelles in 1882 already fully grown and has lived since on the grounds of Plantation House, the governor's residence. Nearly blind and with a poor sense of smell, he is hand-fed by caretakers. In April, false social media posts claimed he had died, and the St Helena government confirmed he was alive, the Associated Press reported.

Clark said a large study found Aldabra tortoises average about 80 years, with a maximum near 96, making Jonathan an outlier — even for his long-lived species. Some experts have suggested from his shell that he may belong to a distinct subspecies of Seychelles tortoise, a debate that remains unsettled.

The researchers plan to sequence more tortoises from Aldabra Atoll in the Seychelles, home to roughly 100,000 of the animals. That work could show whether Jonathan's traits are shared across the population or are his alone, and it could add to knowledge of a species Gerlach and other conservation scientists have studied for decades.

The bottom line is that Jonathan's genes offer intriguing clues, not answers. The next steps are larger comparisons across Aldabra tortoises and, eventually, broader tissue sampling, which together will show whether this record-setting tortoise is a model for longevity or simply an extraordinary individual.

What Readers Want to Know

Who is Jonathan the tortoise?

Jonathan is a giant tortoise on the South Atlantic island of St Helena, believed to have hatched around 1832. Guinness World Records lists him as the oldest known living land animal.

What did the new study find?

Researchers found 287 unique gene variants tied to aging pathways and gene switches linked to energy production that look as young as those of a 5-year-old tortoise.

Does the study explain why Jonathan lives so long?

No. The authors did not establish cause and effect, and independent scientists say Jonathan may simply be an exceptional individual.

How was Jonathan's DNA collected?

His veterinarian collected cheek scrapes because authorities did not allow blood draws, and the first swabs produced bacterial DNA instead of tortoise DNA.

Who funded and led the research?

The study was led by Kallel, a U.S. longevity nonprofit, with collaborators including the University of Cambridge, and was funded by the Voland Fund.

What comes next?

The team plans to sequence more Aldabra tortoises from the Seychelles to see whether Jonathan's genetic traits are shared by others of his species.