A 194-year-old tortoise, world’s oldest land animal, may hold clues to longer life

An Aldabra giant tortoise named Jonathan, believed to be around 194 years old, may hold secrets to a longer life, according to scientists. Living on the remote South Atlantic island of St Helena, Jonathan far exceeds the typical lifespan of his species, which can live for over 100 years. Brought to St Helena as a fully grown adult in 1882, likely from Aldabra Atoll or the granitic Seychelles, Jonathan now resides in a paddock at Plantation House, the governor’s residence.

Researchers sequenced Jonathan’s genome and analyzed his epigenome, the chemical markers that control gene activity. They discovered changes in genes associated with longevity, such as DNA repair, mitochondrial function, insulin regulation, and telomere function. Mitochondria, known as the powerhouses of cells, and insulin help regulate blood sugar by enabling glucose to enter cells for energy. Telomeres are protective caps at the ends of chromosomes that carry genetic information inside cell nuclei.

Comparing Jonathan’s epigenome to those of four other Aldabra tortoises, researchers found that his methylation entropy, a measure of disorder in biochemical processes, was lower than that of every tortoise studied, except a five-year-old juvenile. This suggests that certain regions of Jonathan’s DNA, which act as switches controlling gene expression, remained more youthful than his peers.

Jonathan carries 287 genes with unique variants, including some linked to tumour suppression and DNA repair. He also has extra copies of a gene encoding a protein involved in identifying ageing and cancerous cells. Despite his age, Jonathan remains active and retains a voracious appetite, lifting his head and stretching his long neck when called by his veterinarian, Joe Hollins. Hollins describes Jonathan as a "gentle giant," noting that he knows Hollins’ voice and handling, and recognizes the arrival of a feast.