What Animals Can Live Forever — Or Close To It?

Several real animals have evolved extraordinary biological mechanisms that allow them to live for centuries, regenerate completely from fragments, or even reverse their own ageing — with the immortal jellyfish Turritopsis dohrnii being the only known animal capable of reverting to a juvenile state after reaching full sexual maturity.

The Immortal Jellyfish: Nature’s Reset Button

The most extraordinary longevity trick in the animal kingdom belongs to Turritopsis dohrnii, a translucent jellyfish no larger than a human fingernail. When stressed, injured, or old, this animal does not simply die — it reverts entirely to its juvenile polyp stage through a process called transdifferentiation. Its mature adult cells reprogram themselves into a completely different cell type, effectively resetting the organism’s biological clock to zero. This is not a metaphor. The jellyfish literally starts its life cycle over from scratch, and the process can repeat indefinitely. No other animal on Earth has been confirmed to do this.

The Hydra: A Creature That Does Not Age

If the immortal jellyfish resets its clock, the hydra simply ignores the clock altogether. This tiny freshwater organism — barely ten millimetres long — displays what biologists call negligible senescence: its mortality rate does not increase with age. Studies tracking hydra populations in controlled laboratory conditions for years have found no measurable decline in reproduction rates, no increase in death rates, and no sign of deterioration over time. The hydra continuously regenerates its own tissues, and up to two-thirds of its body is replaced on a regular cycle. Whether a hydra is one year old or one hundred, its biological risk of dying appears to remain exactly the same.

Ming the Clam: 507 Years of Ocean Survival

In 2006, marine scientists dredging the seafloor near Iceland collected an ocean quahog clam and began counting the growth rings on its shell — one ring per year, as reliable as tree rings. The final count: 507 rings, meaning the clam, later named Ming, had been alive since 1499. It had survived five centuries of Atlantic storms, shifting ocean conditions, and fishing activity. Tragically, the act of opening the shell to confirm its age ended Ming’s life, making it one of the most haunting accidental discoveries in marine biology. Ming remains the oldest confirmed individual animal ever recorded at the time of its discovery.

The Planarian Flatworm: 279 Pieces, 279 Survivors

The planarian flatworm holds a regenerative ability that borders on the surreal. A single worm can be cut into as many as 279 separate fragments — and every single fragment will regenerate into a complete, fully functional organism. Fragments with no brain tissue will grow an entirely new brain. This is possible because up to 20 percent of the planarian’s body mass consists of neoblasts — the only known adult stem cells in any animal capable of generating every tissue type in the body. These cells do not age in any meaningful way, continuously refreshing the organism and replacing damaged or old cells. Biologically speaking, the planarian never stops being new.

The Greenland Shark: A Living Vertebrate From the 1600s

Deep in the cold, dark waters of the North Atlantic and Arctic Ocean lives the slowest-growing vertebrate on Earth. The Greenland shark grows at approximately one centimetre per year and does not reach sexual maturity until around the age of 150. Determining its age required an ingenious scientific method: the crystalline proteins inside a Greenland shark’s eye lens form before birth and are never replaced, preserving the radiocarbon signature of the moment the animal was born. Using this technique, researchers in 2016 estimated a female Greenland shark to be approximately 392 years old — born around 1624, before the Mayflower sailed and before Louis XIV was born. She is the oldest known vertebrate animal on Earth.

The Bowhead Whale: Ancient Harpoons and Anti-Ageing DNA

Bowhead whales carry their age in two remarkable ways. First, researchers examining whales caught during indigenous hunts discovered harpoon fragments from the 1800s buried deep in the animals’ blubber — physical proof of lifespans exceeding 100 years without the need for any laboratory analysis. Second, amino acid chemistry in the eye tissue of one bowhead whale estimated its age at over 211 years, placing its birth before the American Civil War, before the Eiffel Tower, and before the invention of the light bulb. Scientists have since identified unique mutations in bowhead whale DNA-repair genes that appear to give these animals an extraordinary capacity to fix genetic damage — a mechanism researchers believe may be directly relevant to understanding human ageing.

The Glass Sponge: Possibly the Oldest Animal Ever

The most staggering lifespan on this list belongs to Monorhaphis chuni, a species of deep-ocean glass sponge. Rigorous scientific analysis has estimated that some individuals of this species may live up to 11,000 years — meaning a single organism could have been alive before the Egyptian pyramids were built, before Stonehenge, and before the first cities appeared on Earth. The glass sponge achieves this in near-freezing, crushing deep-ocean darkness, and its skeleton — made of silica fibres that function as natural fibre-optic cables — represents one of the most remarkable feats of biological engineering ever documented. If those age estimates hold, Monorhaphis chuni is not just the longest-lived animal. It may be the longest-lived individual organism of any kind ever studied.

What These Animals Mean for Human Medicine

Every animal on this list has solved a version of the same biological problem that ageing science is trying to crack: how to prevent or reverse the cellular breakdown that drives age-related disease. Transdifferentiation in jellyfish, neoblasts in planarians, DNA-repair mutations in bowhead whales — these are not curiosities. They are biological blueprints. Researchers studying these organisms are actively working to understand whether the mechanisms that protect them can be translated into therapies for cancer, neurodegeneration, and age-related decline in humans. The answers, if they come, may not come from a laboratory — they may come from a 400-year-old shark swimming silently through Arctic darkness.