- Greenland sharks can live up to 400 years, making them the longest-lived fish.
- Researchers are studying these sharks to uncover the secrets of their long lifespans.
Abigail Adams, wife of the second US president, was born in 1744. It's entirely possible that there are Greenland sharks still living today that were swimming in the North Atlantic Ocean at the time.
There's no doubt that these large, carnivorous sharks can live hundreds of years. In 2016, researchers discovered they can survive for at least 272 years, but they might get as old as 400.
However, why these sharks have that kind of longevity is more of a mystery. Some theories include the shark's slow growth rate and low metabolic rate, but research is ongoing.
Scientists hope that unlocking the secrets of how these fish age could help humans live longer, healthier lives. We probably won't reach age 400, but even extending the average human life by an extra decade would be a breakthrough.
One scientist on the hunt is Ewan Camplisson. He's been studying the sharks' metabolism for clues into its aging process.
"Better understanding the anatomy and adaptations of a long-lived species such as the Greenland shark may allow us to improve human health," Camplisson, a PhD student at the University of Manchester, told Business Insider.
A lifelong slow metabolism
Mostly found in the Arctic and North Atlantic oceans, Greenland sharks are leisurely swimmers that can reach between 8 and 23 feet long and weigh as much as 1.5 tons, according to National Geographic.
The predators feed on salmon, eels, seals, and even polar bears, given the chance. However, they can likely go for long periods between meals. A 493-pound fish could do just fine with between 2 and 6 ounces of food a day, according to a 2022 study.
Camplisson's new research, which he presented at the Society for Experimental Biology Annual Conference earlier this month, showed that sharks' metabolic rate may not slow as they age, which could help explain why the sharks live so long.
The same isn't true for most animals, humans included. For example, human metabolism tends to slow in later years, which can contribute to unhealthy weight gain.
Camplisson looked at the activity of five metabolic enzymes in preserved Greenland shark muscle tissue. "In most species, you would expect as an animal ages for these enzymes' activity to vary," he said.
"Some of them will show reduction over time as they may begin to fail or degrade, while others will then compensate and increase in activity to make sure the animal still produces enough energy," he added.
In the Greenland sharks he looked at, which were estimated to be between 60 and 200 years old, he found no significant variation in the enzyme activity. Of course, a Greenland shark might only be middle-aged at 200, so the same might not hold true as they reach their third or fourth century of life.
Camplisson plans to look at more enzymes to see if and how they change as the sharks age.
Aging is complicated
There's still a lot of work to be done before this kind of research can be applied to humans.
"Aging is an incredibly complex system, and we still don't have a definitive answer to how exactly it works," Camplisson said.
For example, changes in metabolism are just one part of aging in humans. Genetic errors, protein instability, and several other processes are among what's known as the "hallmarks of aging." Camplisson thinks the sharks have more to teach us in these areas.
"We want to look closely at some of these hallmarks to determine if the Greenland shark shows any signs of traditional aging," he said.
While Greenland sharks' remarkable aging process has allowed them to survive centuries, it could also be a double-edged sword as their environment rapidly changes.
The species, which is considered "Near Threatened" by the World Conservation Union, may be too slow to adapt to changes in climate, marine pollution, and other stressors, Camplisson said.