In the icy depths of the North Atlantic and Arctic Oceans swims a creature that defies our typical understanding of age and endurance: the Greenland shark. Known for its remarkable longevity, this elusive species is now recognized as the longest-living vertebrate on Earth. With lifespans estimated to reach up to 400 years, a Greenland shark alive today could have been circling the ocean floor during the time of the Mayflower. This extraordinary fact highlights just how little we still know about the deep-sea world and the ancient creatures that inhabit it.
The Greenland shark, or Somniosus microcephalus, is a slow-moving giant that can grow up to 24 feet long and weigh as much as 2,645 pounds. Despite its size and status as an apex predator, it leads a relatively unhurried life. These sharks grow at a glacial pace—only about 0.4 inches per year—and don’t reach sexual maturity until they are around 150 years old. This slow development is likely one of the reasons they have remained so mysterious for so long.
One of the most compelling aspects of the Greenland shark’s story is how scientists finally unlocked the secret of its age. Traditional methods of aging sharks, such as counting growth rings in hardened tissue, don’t work for this species because it lacks such structures. The breakthrough came from an unexpected source: the eyes. Danish radiocarbon dating expert Jan Heinemeier and his team discovered that the proteins in the lenses of eyes remain stable over time and can be used to determine age. By analyzing the carbon-14 levels in these proteins, researchers were able to estimate the age of individual sharks with surprising accuracy.
This method had already proven useful in forensic investigations, including a peculiar murder case in Germany where the victims had been frozen for years. The team used the same technique to pinpoint the victims’ ages, which helped determine the timeline of the crime. When marine biologist John Fleng Steffensen learned about this approach, he collaborated with Heinemeier to apply it to the Greenland shark. The results confirmed what many had suspected: these sharks are ancient mariners of the deep.
What allows the Greenland shark to live such a long life? Scientists believe several factors contribute to its longevity. Chief among them is the cold environment it inhabits. The frigid waters—hovering around 29 degrees Fahrenheit—are thought to slow down biological processes, including aging. The shark’s low metabolic rate likely plays a role as well, conserving energy and reducing wear on its body over time. Ongoing studies are exploring the shark’s genetic makeup, heart, and immune system in hopes of uncovering more definitive answers. There’s even optimism that these discoveries could lead to advances in human medicine, such as immune-boosting therapies.
Despite their sluggish pace—earning them the nickname “sleeper sharks”—Greenland sharks are capable of short bursts of speed when needed. They are primarily scavengers, often feeding on the carcasses of animals like polar bears and reindeer that have fallen into the ocean. However, they do occasionally hunt live prey, such as seals and fish. This scavenger lifestyle, combined with their deep-sea habitat, means they rarely come into contact with humans.
In fact, sightings of Greenland sharks are uncommon, even for researchers. According to Dr. Steven E. Campana, a professor at the University of Iceland, these sharks are usually caught only as bycatch in fisheries targeting other species. Their deep-water habitat has likely helped them avoid the intense fishing pressures faced by many other shark species. While their exact conservation status remains unclear, some populations appear stable, suggesting that they have not yet been driven into critical decline.
Another curious aspect of the Greenland shark is its vision—or lack thereof. Many individuals have copepod parasites attached to their eyes, which can obscure or even block their vision. There’s no known benefit to the shark from these parasites, and it’s unclear how much they affect the animal’s ability to see. Still, the shark’s other senses likely compensate, allowing it to navigate and find food in the dark, cold waters it calls home.
In Iceland, the Greenland shark has cultural significance as well. Its meat, toxic when fresh due to high levels of urea and trimethylamine oxide, is traditionally fermented and dried to create a local delicacy known as hakarl. This process takes several months and results in a pungent food that’s not for the faint of heart, but remains a symbol of Icelandic heritage and resilience.
I found this detail striking: a creature that may have been alive during the early 1600s is still silently patrolling the depths today. It’s a humbling reminder of the ocean’s vast timelines and the endurance of life in the most extreme environments. As scientists continue to study the Greenland shark, we may uncover not only the secrets of its longevity but also insights that could benefit our own species. For now, it remains one of the ocean’s most fascinating enigmas—a living link to centuries past, quietly gliding through the cold, dark sea.
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