Humans boast the longest average lifespan of any terrestrial mammal, yet several other species can outlast us by decades or even centuries. Tortoises, in particular, are renowned for their slow, steady metabolisms and low heart rates, which enable them to reach and often exceed 100 years of age.
Because tortoises have a metabolic rate that is a fraction of that of a human, they accumulate free radicals—chemicals linked to aging and DNA damage—at a markedly slower pace. The heart of a giant tortoise beats only about ten times per minute, compared with the 60–100 beats per minute typical of an adult human. This sluggish physiology means their bodies experience far less wear and tear, allowing many species to become true centenarians.
As of late 2024, the Guinness World Records lists the Seychelles giant tortoise Jonathan—who resides on the remote Atlantic island of St. Helena—as the longest‑lived land animal. Jonathan is estimated to have been born in 1832, making him older than many of the industrial‑era inventions that revolutionized modern life. A rival, the Aldabra tortoise Adwaita, once the pet of Robert Clive, the first British Governor of India, was believed to have lived well over 250 years before passing away in 2006 at a Kolkata zoo.
Tubeworms are elongated invertebrates that anchor themselves to the seafloor with chitinous tubes—similar to the exoskeletons of crustaceans. Among them, the cold‑seep tubeworms of the Gulf of Mexico captivate scientists with their extraordinary longevity, often reaching ages in the hundreds. These worms have no digestive system; instead, they rely on symbiotic bacteria to extract energy from the chemical-rich cold seeps beneath the ocean floor.
One species, Escarpia laminata, can live more than 300 years. It grows rapidly during its first decade, then slows to a steady 1 cm per year, allowing individuals to reach impressive sizes over centuries.
Deep, cold ocean waters are ideal for long lifespans, as low temperatures suppress metabolic rates. The Greenland shark, found in the Arctic Ocean at temperatures as low as 1 °C, exemplifies this trend. These sharks move slowly—only about 2 mph—and can grow up to 23 ft in length.
In 2016, a study published in Science used radiocarbon dating of eye lenses to determine that the largest specimen—a 16‑ft female—was approximately 392 years old, potentially reaching 512 years. Greenland sharks have a gestation period of up to 18 years and may not reach sexual maturity until around 150 years old, making them the longest‑lived vertebrate known to science.
[Featured image by Hemming1952 via Wikimedia Commons | Cropped and scaled | CC BY-SA 4.0]
Ocean quahogs are large clams inhabiting the North Atlantic. They belong to the ancient family Arcticidae, which has existed since the Jurassic period over 145 million years ago. A quahog discovered off the coast of Iceland in 2006 was carbon‑dated to 507 years old and named Ming, after the Chinese Ming Dynasty. The researchers had to break the shell to determine its age, which unfortunately killed the specimen, but the discovery underscores the remarkable longevity of these mollusks.
Glass sponges, or Hexactinellida, are among the oldest living creatures, first appearing about 570 million years ago. They filter plankton and bacteria through a lattice of silica, giving them a translucent, plant‑like appearance. Recent chemical analyses of their silica structures have revealed specimens older than 11,000 years, with one from the South China Sea estimated at 17,000 years—dating back to the last Ice Age.
Within the Cnidaria phylum, the jellyfish Turritopsis dohrnii—often called the “immortal jellyfish”—exhibits a unique life cycle. After reaching the medusa stage, it can revert to a polyp, effectively resetting its biological age. This process can, in theory, repeat indefinitely, allowing the organism to escape the normal limits of aging.
In 2022, scientists sequenced its genome and identified an abundance of DNA‑repair genes and a mutation that prevents telomere shortening, offering potential insights for regenerative medicine. Although the jellyfish’s tiny size makes it vulnerable to predators, its biological mechanisms are a subject of intense research.
