Jonathan is not simply a giant tortoise: at 192, he is the oldest known land animal. An international research team has analysed his genome to uncover what lies behind his exceptionally long life. Its findings, published in the journal Science Advances, point not only to favourable genes but also to an absence of genetic decay.
Life on St Helena
Jonathan was born around 1832 in the Seychelles. In 1882 he was taken to St Helena, a tropical island in the South Atlantic that is a British Overseas Territory, as a gift to the governor.
He weighs about 200 kilograms and lives with other giant tortoises in the grounds of the governor’s official residence on the island. Although he is blind because of cataracts, he retains excellent hearing.
Genome analysis
The researchers took a small tissue sample from the inside of Jonathan’s cheek for the analysis.
Gene variants linked to longevity
According to the researchers, it was not only good genes that played a role in his longevity, but also the absence of genetic decay. They identified 287 unique gene variants that limit the usual effects of ageing.
These variants control key bodily processes, including:
- repairing DNA damage
- reducing inflammation
- regulating insulin
- suppressing cancer
The role of entropy
The researchers also found that Jonathan’s “secret” appears to be linked to entropy: the tendency of biological systems to become increasingly unstable and disorganised over time.
One of the hallmarks of ageing is mitochondrial dysfunction, which results from rising entropy. Despite his extremely advanced age, Jonathan appears to have largely avoided the effects of this disorganisation.
Further research
Further studies using blood samples from Jonathan will be needed to confirm the findings. Blood samples provide a more complete and “cleaner” DNA sequence.
The researchers also plan to extend their work to other species with exceptionally long lifespans, and to other biological processes associated with ageing.
