ST HELENA, October 08, 2026 (DAILYNWZ) — Jonathan, a 194-year-old Aldabra giant tortoise believed to be the world’s oldest-known terrestrial animal, may owe his exceptional longevity to genetic traits and cellular mechanisms that have remained unusually resilient with age, according to a new study.
Researchers sequenced Jonathan’s genome and examined his epigenome — chemical markers that help regulate whether genes are switched on or off — to investigate how he has survived far beyond the more than 100 years typically reached by members of his species.
The findings, published Wednesday in Science Advances, identified genetic characteristics linked to several biological processes associated with longevity, including DNA repair, mitochondrial function, insulin regulation and telomere maintenance, researcher Benjamin Vaisvil, affiliated with the organization Kallel and a co-lead author of the study, said.
Jonathan was brought to the remote South Atlantic island of St Helena in 1882 as a fully grown tortoise, probably from the Aldabra Atoll or the Granitic Seychelles. He now lives in a paddock at Plantation House, the governor’s residence.
Other Aldabra tortoises have been reported to reach similarly advanced ages, Vaisvil said, but Jonathan has the strongest documentary evidence supporting his age.
Researchers compared Jonathan’s epigenome with those of four other Aldabra tortoises ranging from juveniles to older adults. Because St Helena officials restrict blood draws to reduce infection risks, scientists collected genetic material by scraping tissue beneath Jonathan’s tongue while he was distracted by food.
Vaisvil likened the genome to a cookbook and the epigenome to handwritten notes in its margins. As those notes become harder to read with age, scientists can measure the resulting disorder through what is known as methylation entropy.
Most of Jonathan’s epigenetic markers showed signs of advanced age. But in particular stretches of DNA that regulate genes involved in longevity, his methylation entropy was lower than in every tortoise studied except a five-year-old juvenile, suggesting that some cellular control systems may have remained comparatively youthful.
The researchers also found 287 genes with variants unique to Jonathan, including genes associated with tumour suppression and DNA repair. He additionally carries extra copies of a gene that produces a protein involved in eliminating ageing and cancerous cells.
The findings, however, do not establish why Jonathan has lived so long. “We cannot say for certain that what we found is the reason for his longevity,” Vaisvil said.
Environmental factors may also have played a role. Jonathan lives in a tropical climate and receives a carefully managed diet under veterinary supervision.
The study’s conclusions are limited by its focus on a single exceptionally old animal, making it difficult to determine whether the genetic and epigenetic features identified are unique to Jonathan or shared by other exceptionally long-lived tortoises.
Still, the results broadly resemble findings from research into unusually long-lived humans. Vaisvil pointed to a recent study of a 117-year-old woman that found highly efficient mitochondrial function, similar to patterns identified in some regions of Jonathan’s genome.
Jonathan’s veterinarian and study co-author, Joe Hollins, said the tortoise remains remarkably active and retains a “voracious appetite.” Cataracts have left him mostly blind, but Hollins describes him today as a “gentle giant.”
Jonathan has lived through two world wars and the rise and fall of empires. For St Helena’s residents, Hollins said, he has become a symbol of “resilience, longevity, endurance” and a persistent presence through major historical events.