A Greenland Shark's Heart Is Scarred, Stiff, and 400 Years Old. It's Still Beating.

The Greenland shark doesn't rush anything. Its heart beats about once every 12 seconds. It swims at roughly a foot per second. It grows 1 centimeter (0.4 inch) per year and doesn't reach sexual maturity until its 150th birthday. That's not a typo. That's a teenager.

That pace makes sense for something that routinely outlives entire human generations, with lifespans stretching past 200 years and possibly well beyond 400. But a new study went looking at those hearts, expecting to find some kind of biological secret behind their endurance. What they found instead was the opposite of a secret.

The hearts showed severe fibrosis — scar tissue accumulation that causes stiffness and can impair pumping over time. Lipofuscin, a pigment that accumulates when degraded cellular components aren't cleared properly, was present in large quantities inside the heart muscle cells. In most vertebrates, those findings would be a clinical emergency. In the Greenland shark, they appear to be just Tuesday.

The researchers suggest the shark's extraordinary longevity isn't about avoiding damage; it's about resilience: the ability to maintain physiological function despite age-related deterioration. Its lower blood pressure compared to other species, along with the distinct structure of its ventral aorta, may keep the heart muscle elastic enough to keep working through the wreckage.

Insights into how these animals sustain cardiac function across centuries could open new windows into vertebrate aging, including ours. The researchers also see potential clinical implications, noting that the work may point toward new approaches for addressing age-related heart deterioration in people.

A heart that runs for four centuries on a damaged engine isn't clean biology. It's sheer stubbornness at the cellular level.

Read the full story at Scientific American, May 6, 2026

Hot Take: Every endurance athlete eventually hits a wall where the body is clearly degraded and still somehow performing. Most of us call that mile 22 of a marathon. The Greenland shark has been at mile 22 for about 300 years, and that is either deeply inspiring or deeply unsettling depending on how your training is going.