Jonathan, an Aldabra giant tortoise estimated to be around 194 years old, is regarded as the world’s oldest known land animal. Residing on the remote South Atlantic island of St Helena, he has attracted scientific interest due to his extraordinary longevity and the potential insights it could offer into aging and disease resistance.
Jonathan hatched in the early 19th century, during a period when Charles Darwin was still a young man and Queen Victoria a teenager. He was brought to St Helena as a fully grown tortoise in 1882, likely originating from the Aldabra Atoll or the Granitic Seychelles. He currently lives in a paddock at Plantation House, the residence of the island’s governor.
Researchers have sequenced Jonathan’s genome and studied his epigenome—the chemical modifications regulating gene activity—to better understand the biological foundations of his long life. Their analysis identified 287 genetic features potentially linked to longevity, including variants associated with DNA repair, tumor suppression, mitochondrial function, insulin regulation, and telomere maintenance. These genes may contribute to the tortoise’s ability to maintain cellular health and resist the molecular damage that typically accumulates with age.
Jonathan also shows a remarkable capacity to preserve the integrity of key genomic regions. While DNA can degrade over time—compared to the yellowing and fraying of book pages—the “methylation entropy,” or disorder in gene regulation patterns around longevity-associated genes, was found in Jonathan to be as low as in much younger tortoises. This suggests an epigenetic mechanism helping to maintain youthful cellular function.
Scientists caution, however, that the study focused on a single individual, making it difficult to determine whether these genetic traits are unique to Jonathan or common among his species. Environmental factors likely play a role as well; Jonathan’s tropical island habitat, optimal diet, and regular veterinary care might contribute to his survival beyond typical lifespans seen in Aldabra tortoises that can live over 100 years.
Jonathan’s longtime veterinarian described the tortoise as a “gentle giant” who retains a strong appetite despite some vision loss due to cataracts. He remains well-known and cherished by the island community, symbolizing resilience and endurance through nearly two centuries marked by significant global historical events.
Scientists involved in the research hope that evolutionary insights gleaned from Jonathan’s genome may inform the development of therapies aimed at improving human health and extending lifespan by targeting mechanisms related to aging and chronic disease. While definitive conclusions about longevity cannot yet be drawn, the tortoise’s unique biological profile provides a valuable model for further study of aging across species.