A new study published in Science Advances examined Jonathan’s genome, the complete set of his DNA, as well as his epigenome, which controls how genes are switched on and off. Researchers identified 287 gene variants linked to protecting his cells from damage that builds up with age.
Why Jonathan may age differently
One possible explanation is that Jonathan’s body works at a slower pace.
“The assumption has always been that their metabolic rate is very low compared to us,” study coauthor Justin Gerlach, a fellow in biology at the University of Cambridge, told CNN.
“That means that the processes that are going on inside the cells are slower, so there are fewer chemical reactions and therefore less damage to the cells and to the DNA,” he said.
The researchers found that Jonathan has genes linked to DNA repair and reducing inflammation. They also found that he appears able to keep expressing the right genes at the right levels even at his advanced age.
“Our cells start doing the wrong things and we get cancers, for example. But Jonathan has still got the genetic controls of a much younger animal,” Gerlach said.
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“We don’t know whether that’s because he is exceptional, or whether actually that’s what giant tortoises do,” he added. “But it does mean that their bodies are much fitter than we would expect for their age, compared to what would happen with humans.”
His cells may hold another clue
The study also found that Jonathan’s mitochondria, the structures inside cells that produce energy, were in surprisingly good condition.
Stephen Clark, the senior study author and founder of the Kallel Foundation, said the researchers do not yet know whether this is common among Aldabra tortoises. The team plans to study other tortoises to find out.
Clark said Jonathan’s genome could offer a map for understanding cellular resilience and potentially help researchers identify treatments that improve mitochondrial health.
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More tortoises are needed
Scientists caution that one animal is not enough to explain why some species live much longer than others. More Aldabra tortoises and other long-lived animals will need to be studied to identify the genetic traits responsible for exceptional longevity.
Jonathan’s exact age is not known. Scientists estimate he is around 194 based on an 1882 photograph that shows him already at adult size. Giant tortoises typically reach that size at about 50 years old, meaning Jonathan could potentially be even older.
He weighs about 180 kilograms and remains active despite having lost his eyesight to cataracts. Researchers hope that studying animals like Jonathan could eventually offer clues for understanding ageing, cancer and cellular health in humans.