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October 7, 20263 min read Add Us On GoogleAdd SciAmThe oldest known land animal is 194. How did he get so ancient? The secret to Jonathan the tortoise’s extreme longevity may be in keeping genes tidyBy Jacek Krywko edited by Sarah Lewin FrasierJonathan the Aldabra giant tortoise is the oldest known land animal. Gianluigi Guercia/AFP/Getty ImagesJonathan, an Aldabra giant tortoise on the South Atlantic island of Saint Helena, appears fully grown in a photograph researchers say was taken around 1882. That means he’s survived to at least 194 years old, about a century past his species’ usual upper limit. In a new Science Advances study, scientists read his DNA to try and figure out why. To get the tortoise’s DNA material, Jonathan’s veterinarian Joe Hollins pretended to feed him, wedged his mouth open with a hard glove and scraped cells from inside his cheek. “It was quite tricky and dangerous,” says study co-author Stephen Clark, a researcher at the Kallel Foundation, a longevity nonprofit in Nashville. But it was worth the maneuver: the researchers found that, compared with other Aldabra tortoises, Jonathan has unique variants in 287 genes, some involved in DNA repair.