Jonathan at his home on St. Helena. Credit: St. Helena Government Communication Hub.
Nearly 200-Year-Old Tortoise Has Younger-Looking DNA in 272 Spots
In A Nutshell
- Jonathan, an estimated 194-year-old tortoise, outlived his species’ typical limit by about a century.
- DNA markings near 272 of his genes look tidy, like those of younger tortoises.
- Dozens of those genes help with cell energy or RNA processing.
- Only five tortoises were studied, and the explanation remains unproven.
At an estimated 194 years old, Jonathan, an Aldabra giant tortoise, has outlived the typical upper limit for his species by roughly a century. Scientists studying his DNA now think they may have spotted part of the reason. Chemical markings near 272 of his genes, including ones tied to how cells make energy, look more like those of a young tortoise than an old one.
Those markings, called methylation, work like tags that help switch genes on and off. In people and in the tortoises studied here, the tags tend to get messier with age. Near those 272 genes, Jonathan’s tags stayed tidy, matching a 5-year-old and a 12-year-old tortoise rather than two older adults estimated at about 91.
Senior author Stephen Clark believes the pattern could someday help people stay healthy longer, according to a Vanderbilt Health news release. Published in Science Advances, the study itself involved no humans and could not prove the tidy tags cause long life.
Researchers Studied the Oldest Tortoise Without Drawing Blood
Getting DNA from an island icon took some creativity. Officials on St. Helena, the remote South Atlantic island where Jonathan lives, would not allow a blood draw, citing concerns for his health. Instead, researchers collected saliva and scrapings from inside his mouth. A researcher pretended to feed him, and when he began biting at the air, held his mouth open with a gloved hand while scraping under his tongue with the other.
Those samples could not supply the long, intact strands of DNA that the most detailed methods require, so the team turned to Tank, a 36-year-old tortoise living in captivity, whose blood supplied cleaner DNA to use as a comparison.
To see how the markings change with age, the team compared Jonathan with four other Aldabra giant tortoises: a 5-year-old, a 12-year-old, and two older adult males named Toka and Poka. Their exact ages were unknown, though both were already adults in 1969.
Genetic Clues Point to Aldabra Atoll as Jonathan’s Likely Origin
Jonathan’s DNA also hinted at where he came from. Aldabra tortoises are thought to have spread from East Africa to Madagascar, then to the Seychelles, and finally to the Aldabra atoll, now home to about 100,000 of them. Jonathan did not neatly match any one population on the atoll the way Tank did, and part of his ancestry traced to an unknown source.
Two explanations fit. He may have been removed from the atoll long before the other sampled tortoises, or he may have come from the Granitic Seychelles, a set of islands where sailors likely wiped out the tortoises by the early 19th century. Given his estimated age, the researchers judged the first option more probable, though his exact origin remains unclear.
Oldest Tortoise Shows Orderly DNA Patterns at 272 Gene Switches
Messy tags near a gene’s on/off switch, known as a promoter, are linked to erratic gene activity.
Across his genome as a whole, Jonathan looked his age. His tags were messier than the 5-year-old’s, and disorder rose with age across all five tortoises. Promoters were the exception, since all five animals had fairly orderly patterns there.
A closer look found the key difference: 272 promoters that were tidy in Jonathan and the two youngest tortoises but messy in the two older adults, out of roughly 2,900 with enough data. Nearly 30 percent of those 272 genes are tied to processes already connected to aging, and dozens help mitochondria, the cell’s power plants, make energy or help process RNA, the molecule that carries genetic instructions from DNA to the rest of the cell. A 2025 study of a 117-year-old woman, the longest-lived verified human, found unusually efficient mitochondria too, and orderly RNA-processing genes have turned up in research on long-lived people.
Researchers Propose an Energy and Repair Loop Behind Tortoise Longevity
From that pattern, the team proposed a self-feeding loop. Well-run mitochondria could power better DNA repair, better repair could keep the on/off switches for energy and repair genes tidy, and tidy switches could keep the mitochondria running well.
Authors of the study call the loop a hypothesis. They could evaluate only about 10 percent of the tortoise’s promoters, and they could not measure whether gene activity actually differed.
Jonathan’s own genes may play a part, too. Among longevity-related genes studied before in tortoises, 287 carried changes found only in him, not in Tank, in Lonesome George (a Galápagos giant tortoise), or in humans. He also has 10 copies of the gene for perforin, a protein immune cells use to destroy worn-out and cancerous cells, compared with 7 in Lonesome George. Extra copies could potentially strengthen that cleanup, the researchers noted, though they did not test it.
Five tortoises cannot settle why Jonathan has lasted so long. But tidy switches near energy-making genes give researchers a concrete place to look, and measuring gene activity directly in more animals would show whether the pattern protects anything at all.
Disclaimer: This article is for informational purposes only and is not medical advice. The study examined tortoises, not people, and its findings should not guide personal health decisions. Readers with questions about aging or longevity should consult a qualified health professional.
Paper Notes
Limitations
Researchers could not draw blood from Jonathan, because St. Helena officials restricted blood draws to prevent any risk of infection. That ruled out long-read DNA sequencing, RNA analysis, and tests of how his unique variants affect gene activity. It also left the team relying on mouth-scrape DNA for the methylation comparisons, which covered fewer gene promoters than blood would have. Only five tortoises were included in the methylation comparison, and the exact ages of the two older adults were unknown. Only about 10 percent of the tortoise’s promoters could be evaluated, so the proposed energy and repair loop remains a hypothesis rather than a demonstrated cause. More animal data are needed to learn whether the patterns are specific to Aldabra tortoises or reflect aging more broadly.
Funding and Disclosures
Research support came from the Voland Fund, in memory of Stephen Voland. The authors declared no competing interests. A Vanderbilt Health news release says the Stephen Voland Research Fund provided $50,000 and identifies corresponding author Stephen W. Clark as president and chief scientist of the Kallel Foundation, a nonprofit longevity research group. Listed author affiliations include private companies such as Igenbio, Inc. and Epiphany Biosciences, as well as SeaWorld of Texas and United Parks and Resorts. Before peer review, the authors used Google’s Gemini Advanced 2.0 to reduce the manuscript’s word count by about 30 percent, then edited the shortened version to maintain essential information and avoid hallucinations.
Publication Details
Authors Benjamin Vaisvil, Daniel P. Schmitt, Angela Jones, Vinayak Kapatral, James M. Ford, Madison L. Taylor, Mathia Colwell, Jonathan Hollins, Sam Pascucci, Konstantin Weissenow, Burkhard Rost, Pascal Notin, Justin Gerlach, Thomas C. Terwilliger, Li-Wei Hung, Lars Juhl Jensen, Kathlyn Reed, Todd R. Robeck, Steve Horvath, Christopher Faulk, Yanjun Ma, and Stephen W. Clark (corresponding author, Kallel Foundation, Nashville, Tennessee) wrote the study, titled “Epigenetic insights into extreme longevity in the world’s oldest terrestrial animal, Jonathan.” It was published in Science Advances, Volume 12, Issue 41, article eadw8887, on October 7, 2026, after being submitted February 19, 2025, and accepted August 31, 2026. DOI: 10.1126/sciadv.adw8887.
