Jonathan the tortoise, recognized as the world’s oldest living land animal, is approximately 194 years old. A study published on October 7, 2026, in Science Advances details the sequencing of Jonathan’s genome, providing insights into his longevity.
Jonathan, an Aldabra giant tortoise (Aldabrachelys gigantea), hatched around 1832 in the Seychelles archipelago. He was in his twenties when Charles Darwin published On the Origin of Species and was brought to Saint Helena in the 1880s as a gift to the British colonial governor. He has resided there ever since.
While Aldabra giant tortoises typically live for over a century, Jonathan is an exceptional case as he nears 200 years of age. Researchers conducted a genomic evaluation using cheek swabs and compared Jonathan’s genome with that of other tortoises, including a 36-year-old named Tank.
The findings indicated that Jonathan possesses unique gene variants in several aging pathways, which include DNA repair, insulin regulation, mitochondrial function, and low entropy methylation. Stephen Clark, an aging researcher at the Kallel Foundation and co-author of the study, noted, "Aging is very complicated, and there's all these different hallmarks. That's why this Jonathan study is so interesting. We're still just at the very beginning of trying to understand aging."
The research process began in 2017, with challenges in obtaining genetic information. A blood draw was considered too risky, leading to the decision to use a swab instead. Delays occurred due to incomplete early samples, the Covid pandemic, and new regulations. Eventually, samples were transported from Saint Helena to Florida by the U.S. Space Force.
The analysis revealed that Jonathan had gene variants typically associated with long-lived individuals, including those related to DNA repair and cellular recycling (autophagy). A notable finding was in Jonathan’s methylome, particularly concerning mitochondrial processes, which appeared unusually pristine. Clark stated, "Jonathan's really the first of his kind to have this analysis, and we were also able to do the methylome for the younger tortoises. We actually compared him to a five-year-old tortoise, so we had 189 years of difference between the methylomes."
While most of Jonathan’s genome showed age-related entropy, his mitochondrial methylome resembled that of the younger tortoise, suggesting that these pathways may significantly contribute to his longevity. Clark emphasized that further research is needed to explore the complex genetic factors influencing aging.
The Kallel Labs team aims to study long-lived species like Jonathan to identify potential targets for enhancing human healthspan and lifespan. Currently, Jonathan resides at the governor’s residence, Plantation House, where he and other tortoises attract tourists. Saint Helena is also historically significant as the exile location of Napoleon Bonaparte, who died there shortly before Jonathan's estimated hatching. Jonathan’s long life reflects the vast changes in the world over nearly two centuries.