St Helena: The world’s oldest-known terrestrial animal, an Aldabra giant tortoise named Jonathan and estimated to be about 194 years old, may owe his extraordinary longevity to a combination of genetic traits and an ability to keep key cellular systems functioning in a more youthful way, according to scientists.

Members of this species are known to live more than 100 years, but Jonathan has far exceeded that. Brought to the remote South Atlantic island of St Helena as a fully grown animal in 1882, likely from the Aldabra Atoll or the Granitic Seychelles, the tortoise now resides in a paddock at Plantation House, the governor’s residence.

“Other Aldabra tortoises have been claimed to have lived as long as Jonathan, but he has the most documentary evidence supporting his age,” said Benjamin Vaisvil, a researcher affiliated with the organisation Kallel and co-lead author of the study published on Wednesday in the journal Science Advances.

Scientists have studied Jonathan to explore the secrets of the animal’s amazing longevity, sequencing his genome and analysing his epigenome the chemical markers that control which genes switch on and off. “We found changes in Jonathan’s genome in pathways associated with longevity, like DNA repair, mitochondrial function, insulin regulation and telomere function,” Vaisvil said.

Mitochondria are structures considered the powerhouse of a cell. Insulin is a hormone that helps regulate levels of blood sugar by letting it enter the body’s cells for energy.

Telomeres are protective caps at the ends of chromosomes, structures that carry genetic information inside cell nuclei. Researchers compared Jonathan’s epigenome with four other Aldabra tortoises, ranging from juveniles to older adults.

Published in Dawn, October 8th, 2026