At 194, the world's oldest land animal kept its mitochondrial genes young

Jonathan the tortoise was already a fully grown adult when Abraham Lincoln and Charles Darwin were in their heyday. Now, at an estimated 194 years old, the Aldabra giant tortoise on the island of St Helena has given scientists something remarkable: a new study in Science Advances found that the gene switches controlling his mitochondrial function look as young as a 5-year-old tortoise's — even as the rest of his genome shows nearly two centuries of wear.

Young switches in a two-century-old animal

An international team led by Dr. Stephen Clark of the nonprofit Kallel Labs and Dr. Justin Gerlach of the University of Cambridge sequenced Jonathan's genome and epigenome and compared it with four other Aldabra tortoises, ranging from a 5-year-old to adults in their 90s. Beyond the 287 unique gene variants — touching DNA repair, telomere maintenance, insulin regulation, mitochondrial function, and cancer pathways — the standout finding was epigenetic: promoters for genes involved mainly in mitochondrial function and RNA processing had stayed remarkably youthful in Jonathan.

"He has some genes that further slow the effects of ageing – by repairing DNA, for example – but also has particularly stable gene regulators that keep his cells working properly long after ours would have run into problems," Gerlach said.

What one tortoise can — and can't — teach us

Jonathan's 91-year-old counterparts showed deeply aged versions of the same promoters — the difference, the researchers suspect, is that his mitochondria are effectively younger-acting. The team is now planning to sequence more Aldabras from the Aldabra atoll's population of around 100,000 to learn how unusual Jonathan really is; he may even belong to a longer-lived subspecies.

One tortoise does not make a longevity protocol. But the finding lands squarely on a growing model of extreme aging: that keeping mitochondrial gene regulation stable may be central to keeping the whole organism running far past its warranty. For a site devoted to mitochondria, it is hard to imagine a more vivid illustration.

Where the evidence stands

• Established: Jonathan is around 192–194 years old — exceptional for his species, whose average lifespan is about 80 and maximum about 96; sequencing revealed 287 unique gene variants across aging pathways.
• Preliminary: 272 genes — mainly involved in mitochondrial function and RNA processing — had promoters as youthful as a 5-year-old tortoise's in Jonathan, versus deeply aged in two 91-year-old Aldabras; a single-animal epigenome comparison, so the longevity link is suggestive, not proven.
• Absent: Proof that these gene switches are why Jonathan lived so long; any application to human aging.