Jonathan the Tortoise’s Genetic Blueprint Revealed as Scientists Decode 194-Year Longevity

Scientists have identified specific genetic and epigenetic characteristics that may explain how Jonathan, an Aldabra giant tortoise residing on the remote South Atlantic island of St. Helena, has reached the remarkable age of 194. Living approximately a century beyond the typical lifespan for his species, Jonathan’s genomic profile offers new insights into the mechanisms of extreme longevity.

The study, published Wednesday in the journal Science Advances, examined not only the tortoise’s DNA but also epigenetic markers—chemical tags that regulate gene activity without altering the underlying genetic code. According to the findings, genes associated with mitochondrial function appear to be in exceptional condition epigenetically, a factor researchers believe played a significant role in the animal’s survival.

Stephen Clark, chief scientist at the Kallel Foundation, a Nashville-based nonprofit focused on identifying drug targets for human longevity, emphasized the importance of these findings. While mitochondrial health has long been connected to aging and disease, this research provides a fresh perspective on that dynamic through the lens of one of the planet’s longest-living creatures.

Obtaining the data required overcoming significant hurdles. Nearly a decade ago, the team recruited Joe Hollins, the veterinarian responsible for Jonathan’s care, to collect samples. Because island authorities prohibited blood draws due to infection risks, Hollins initially used cheek swabs. However, when the sequencing computers repeatedly crashed upon analysis of the returned samples, the team discovered the DNA had originated from oral bacteria rather than the tortoise itself.

Clark recounted having to request permission to collect additional data. The vet subsequently sent cheek scrape samples using a different tool, which successfully yielded Jonathan’s own DNA. Because the DNA extracted from these tissue samples was more fragmented than blood-derived DNA, researchers utilized a reference genome from Tank, a 36-year-old Aldabra tortoise, to fill in the gaps. They also compared Jonathan’s genetic material to that of Lonesome George, a Galápagos tortoise who died in 2012 at an estimated age of over 100.

The analysis revealed that Jonathan possesses 287 unique gene variants previously linked to aging-related pathways, including those involved in DNA repair and telomere function—the protective caps at the ends of chromosomes that typically shorten as organisms age. Greer Dolby, an assistant professor of biology at the University of Alabama at Birmingham who was not involved in the study, noted that these pathways mirror aging processes in humans, indicating a broader signature of aging across species.

The researchers also investigated DNA methylation patterns, where methyl groups bind to DNA to influence gene expression. In older tortoises, these patterns tend to become disordered, a phenomenon described by scientists as “methylation entropy.” While Jonathan’s methylation patterns were more disordered than those of young tortoises overall, they remained highly organized in the sections of genes responsible for switching mitochondrial functions on.

“Keeping the entropy low in these mitochondrial genes, or keeping pristine mitochondria, is likely to be a contributor to longevity,” Clark said. Mitochondria are essential for producing cellular energy, facilitating repair, and minimizing DNA damage.

Despite these discoveries, the study authors acknowledged they could not establish a causal link between Jonathan’s low entropy in mitochondrial genes and his lifespan, as they did not conduct experiments to definitively prove the connection. Clark suggested that future blood sample analyses could provide a more comprehensive view of the genome.

Vincent Lynch, a biology professor at the University at Buffalo, pointed out that Jonathan’s full genetic profile cannot be completely determined until after his death, when DNA can be collected from various tissues. He also questioned whether methylation entropy is a reliable metric for age-related changes, noting that methylation patterns can be unpredictable. Nevertheless, Lynch agreed that the flagged genes provide valuable data for future longevity research.

The researchers stressed that further experiments are necessary to determine whether these mitochondrial genes contribute to longevity across all Aldabra tortoises and other species, or if Jonathan is merely an outlier. As Lynch summarized, “Maybe Jonathan is just really good at being old.”