Jonathan the giant tortoise, 194, offers up insight into secrets of longevity

The remote South Atlantic island of St. Helena is home to Jonathan, the world's oldest living land animal, who has surpassed the expected lifespan of an Aldabra giant tortoise by almost a century. Scientists have recently identified several unique genetic and epigenetic traits that may contribute to Jonathan's remarkable longevity. The study, published in Science Advances, examined Jonathan's genes and the chemical tags (epigenetic markers) that control gene activation.

Jonathan's genes associated with mitochondrial function were in excellent condition, suggesting a significant role in his longevity. Mitochondrial dysfunction is often linked to disease, but Jonathan's case offers new insights into the relationship between longevity and mitochondrial health. The research was led by Stephen Clark, chief scientist of the Kallel Foundation, a nonprofit focused on drug targets to promote human longevity.

In 2017, researchers gathered samples from Jonathan using cheek swabs, after being denied permission to collect blood due to infection risks. When the samples arrived in the U.S., it was discovered that the DNA had been isolated from bacteria in Jonathan's mouth rather than his cells. The researchers were able to obtain more samples through cheek scrapes, which contained the actual tortoise DNA.

The study compared Jonathan's genetic makeup to that of two other tortoises, Tank, aged 36, and Lonesome George, who died at around 100 years old. Jonathan carried 287 unique variants of genes linked to aging-related pathways, including those involved in DNA repair and telomere function. Similar pathways are also implicated in aging processes in humans.

The researchers also analyzed epigenetic changes, such as DNA methylation, which can act as a biological age clock. In most genes, Jonathan's DNA methylation patterns were more disordered than those of younger tortoises. However, in genes related to mitochondrial function, Jonathan exhibited more organized methylation patterns, which may help maintain consistent gene expression and contribute to his long life.