The ancient quest to extend human lifespan has received a boost after scientists analysed the genetic code of the world’s oldest living land animal, a giant tortoise called Jonathan.
The tortoise, which lives in the grounds of Plantation House, the official residence of the governor of Saint Helena in the South Atlantic, is believed to be 194 years old, making him a contemporary of Queen Victoria and Charles Darwin.
Analysis of the animal’s DNA revealed a host of genetic variants in most of the biological pathways for ageing that scientists have discovered. Together, they help organisms to survive by repairing damaged DNA, regulating their metabolism and fending off cancer.
But more intriguing to the researchers were chemical patterns on Jonathan’s genes that appear to protect the healthy functioning of his mitochondria, the tiny battery-like structures that power biological cells. Ailing mitochondria have been strongly linked to ageing and age-related diseases.
“We’re still trying to work out how ageing occurs and Jonathan gives us a real window on to what happens over a long period of time,” said Stephen Clark, a senior researcher on the project at the non-profit Kallel Foundation. “His mitochondria must be especially stable and that’s an insight into longevity in general. It’s important that the mitochondria are kept as pristine as possible.”
The insight came when the international team, led by Benjamin Vaisvil, looked at chemical tags that attach to DNA, creating patterns that change over time. The tags, known as methyl groups, typically silence the genes they latch on to.
Writing in Science Advances, the researchers describe how they compared the methylation patterns on Jonathan’s genes with those from other giant tortoises. The patterns on many of his genes were similar to those of other old tortoises, but the patterns on genes linked to mitochondrial function matched those from much younger animals.
It is unclear whether, or how much, the chemical patterning contributes to Jonathan’s impressive lifespan. Clark said the team now needed to validate the finding. “How do we test this idea?” he said. “Is there a way that makes the mitochondria young, or can we replace the mitochondria and see if it extends longevity? That’s one of the next steps.”
The former senior veterinary officer of Saint Helena, Joe Hollis, took over Jonathan’s care in 2009. He was not faring well at the time. Cataracts had left him blind, he had lost his sense of smell and his beak was soft and crumbly, making it hard to forage. Hollis began hand-feeding him and six months to a year later, the tortoise had regained weight and sported a hard, serrated beak.
In April, Jonathan was caught up in a viral crypto death scam when a message from a fake X account posing as Hollis claimed the tortoise had died. The news spread around the world before the Guardian made contact with Nigel Phillips, the governor of Saint Helena, who interrupted his bedtime routine to check on Jonathan. He found him asleep under a tree but “very much alive”.
Jonathan certainly appears to be enjoying life. A few months ago, he was found mating with Emma, who shares his paddock. Shortly afterwards, the wife of the governor, who is also called Emma, checked on Jonathan and found him upside down. “Emma [the tortoise] has a very semicircular shell,” said Hollis. “So if you slip sideways fast enough the momentum will flip you right over. It’s phenomenal though. He’s 194. You’re going to have an accident, aren’t you, at 194?”
