The animal kingdom holds creatures that defy typical lifespans, living for centuries. These organisms offer a glimpse into the remarkable resilience and adaptability of life on Earth. Their extraordinary longevity reveals how some species slow aging, survive harsh conditions, and persist.
The Reigning Champion
The animal currently recognized as the oldest known vertebrate on Earth is the Greenland shark (Somniosus microcephalus). This remarkable species inhabits the frigid, deep waters of the North Atlantic and Arctic Oceans. Scientists estimate that Greenland sharks can live for at least 250 years, with some individuals potentially exceeding 500 years. One large female, measuring about 5 meters, was estimated to be between 272 and 512 years old.
Greenland sharks are large, reaching lengths of up to 7 meters (23 feet) and weighing over 1,000 kilograms (2,200 pounds). They are slow-moving creatures, typically swimming at less than 3 kilometers per hour (1.9 miles per hour), earning them the nickname “sleeper sharks” due to their sluggish nature. Their diet consists of various fish, including smaller sharks, eels, and flounders, and they also scavenge on carrion, such as polar bears and reindeer that fall into the ocean.
Unlocking Their Age Secrets
Determining the age of long-lived animals, especially those without easily identifiable growth markers, presents a significant scientific challenge. For many shark species, age can be estimated by counting growth bands on fin spines or vertebrae, similar to tree rings. However, Greenland sharks lack fin spines and possess soft vertebral tissues that do not form such bands.
A breakthrough occurred with the application of radiocarbon dating to the proteins within the shark’s eye lenses. These proteins are formed before birth and do not degrade over the animal’s lifetime, preserving a chronological record. Scientists analyzed the levels of carbon-14, a naturally occurring radioactive isotope, in the eye lens nuclei of 28 female Greenland sharks. The presence of a “bomb pulse” signature from nuclear testing in the mid-20th century helped establish a clear reference point for dating younger individuals. This method revealed their exceptional longevity.
Biological Adaptations for Extreme Lifespans
The extraordinary longevity of animals like the Greenland shark is linked to several biological and environmental factors. A key adaptation is their very slow metabolism, a characteristic often found in species residing in cold, deep-sea environments. The consistently low temperatures of the Arctic Ocean, where Greenland sharks live year-round, slow down their biological processes, including growth and aging. This reduced metabolic rate conserves energy and may also decrease the accumulation of cellular damage over time.
Greenland sharks grow less than one centimeter per year, and females do not reach sexual maturity until they are around 150 years old. This incredibly slow growth and reproductive rate are direct consequences of their low metabolic activity and the cold habitat. Additionally, their deep-sea habitat offers a relative lack of predation, which contributes to their long survival. While cellular repair mechanisms are investigated, a slow pace of life in a stable, cold environment likely minimizes cellular wear and tear, contributing to their impressive lifespans.
Other Ancient Life Forms
While the Greenland shark holds the record for the longest-lived vertebrate, other animals also exhibit remarkable longevity.
Ocean Quahog
The ocean quahog (Arctica islandica), a type of bivalve mollusk, is considered the longest-lived non-colonial animal, with one individual, nicknamed “Ming,” estimated to be 507 years old. Its age is determined by counting annual growth rings on its shell, similar to tree rings. These clams live buried in sandy seabeds of the North Atlantic, growing slowly in cold waters.
Bowhead Whale
Another long-lived mammal is the bowhead whale (Balaena mysticetus), found in the Arctic and subarctic waters. These whales can live for over 200 years, with one specimen estimated to be 211 years old. Their longevity is partly attributed to their slow growth rate and unique genes that may contribute to DNA repair and cancer resistance.
Immortal Jellyfish
In contrast to these long-lived vertebrates, the immortal jellyfish (Turritopsis dohrnii) possesses a unique ability to revert to an immature polyp stage after reaching sexual maturity, theoretically allowing it to escape death by aging. While not truly immortal due to predation and disease, its capacity for biological “reset” is an extraordinary adaptation.
Glass Sponges
Glass sponges, found in deep oceans worldwide, are also thought to be among the longest-lived animals. Some estimates suggest they can live for over 10,000 years, possibly up to 15,000 years, due to their extremely slow metabolism in cold, nutrient-scarce environments.