The question of the oldest animal ever recorded does not have a single, simple answer, as the record holders occupy wildly different biological categories. Animal longevity spans from short lifecycles to spans that dwarf human civilization, often depending on how age is defined and measured. The true record is held by obscure, slow-growing organisms, while the most impressive lifespans among mobile animals are measured in centuries. Exploring these forms of extreme age reveals a fascinating biological landscape where species have evolved unique strategies to resist aging.
Defining Longevity: Measured Age vs. Biological Immortality
Understanding extreme longevity requires distinguishing between a maximum measured lifespan and biological immortality. Maximum measured lifespan refers to the verifiable age of an individual organism before death, often determined by counting physical growth markers.
Biological immortality describes a state where an organism does not age or displays negligible senescence, meaning its probability of death does not increase with time. The hydrozoan Turritopsis dohrnii, commonly called the immortal jellyfish, exemplifies this concept. When faced with environmental stress or physical damage, this tiny animal can revert its entire adult body back to its juvenile polyp stage through a process called transdifferentiation. This biological reversal allows the jellyfish to restart its life cycle indefinitely, preventing death from old age, although individuals can still succumb to disease or predation.
The Undisputed Record Holders: Sessile Invertebrates
The absolute longest lifespans belong to animals that remain fixed in one place, or sessile, and possess extremely slow metabolisms.
Ocean Quahog
The Ocean Quahog (Arctica islandica), a bivalve mollusk found in the cold North Atlantic, holds the official record for the longest-lived individual non-colonial animal. Scientists determine the age of these clams by counting the annual growth rings, or annuli, etched into the hinge ligament of their shells. The clam nicknamed “Ming,” harvested off the coast of Iceland, was determined to have lived for 507 years.
Deep-Sea Sponges
The most stunning estimates of longevity belong to the deep-sea glass sponges of the class Hexactinellida. These organisms anchor themselves to the seafloor and construct intricate skeletons from glass-like silica spicules. Because they live in the cold, stable environment of the deep ocean, their growth rates are incredibly slow. Estimates for the maximum age of some Antarctic and deep-sea glass sponges, such as Scolymastra joubini, reach as high as 10,000 to 15,000 years. These figures are based on measuring the extremely slow deposition rate of their silica structures, suggesting they are the longest-lived animals on Earth.
Extreme Lifespans in Mobile Animals
Among animals that actively move, the record for the longest-lived vertebrate belongs to the Greenland shark (Somniosus microcephalus). Found in the frigid, deep waters of the North Atlantic and Arctic Oceans, the slow metabolism of this large predator contributes to its exceptional lifespan. The age of Greenland sharks is calculated using radiocarbon dating of proteins in the nucleus of the eye lens. The largest specimens studied have an estimated age of approximately 392 years, with a possible range between 272 and 512 years. Female Greenland sharks do not reach sexual maturity until they are about 150 to 156 years old.
The Bowhead Whale (Balaena mysticetus) holds the title for the longest-lived mammal, with individuals estimated to live for over 200 years. Scientists determined this age by analyzing the ratio of certain amino acids in their eye lenses, a technique known as aspartic acid racemization.
Reptiles also exhibit remarkable lifespans, with Giant Tortoises being the most famous terrestrial examples. Several species, including the Aldabra and Seychelles giant tortoises, routinely surpass the century mark. One specific Aldabra giant tortoise named Adwaita was documented to have lived for an estimated 255 years in captivity. Jonathan, a Seychelles giant tortoise, is currently the oldest living land animal, having recently passed the age of 190 years.
The Biology of Extreme Longevity
The ability of these animals to live for centuries is fundamentally linked to their physiological and genetic adaptations. A common factor across many long-lived marine species, such as the Greenland shark and the Ocean Quahog, is an extremely slow metabolism. Living in cold, deep-sea environments reduces the rate of cellular damage caused by metabolic byproducts, often referred to as the rate of living theory. This low energy output minimizes the wear and tear on the body’s tissues over time.
Extreme longevity is often tied to highly efficient systems for maintaining cellular integrity. Long-lived species frequently possess robust DNA repair mechanisms that can quickly and accurately correct genetic damage. They also often exhibit specialized anti-cancer mechanisms, which are necessary for organisms that accumulate a vast number of cells over hundreds of years. The suppression or complete absence of senescence, the age-related decline in biological functions, is a hallmark of these long-lived animals.