While empires rose and fell, wars were fought, continents were mapped, and humanity transitioned from candlelight to digital screens, this apex predator swam onward. It navigated the pitch-black abyss through centuries of shifting ocean currents, completely indifferent to the storms raging on the surface above.
Unlocking the Ocean's Vault: The Science of Eye Lenses
For decades, determining the age of sharks presented an insurmountable wall to marine researchers. Traditional methods of aging fish and sharks typically rely on counting calcified growth rings—much like counting the rings of a tree—found in hard structures such as ear bones (otoliths), vertebrae, or fin spines. However, the Greenland shark possesses a uniquely soft, cartilaginous skeleton. Its body lacks the rigid growth structures necessary for conventional aging techniques.
Desperate for an alternative metric, Nielsen and his colleagues turned to a revolutionary biochemical approach: radiocarbon dating of the eye lenses.
As detailed by Smithsonian Ocean researchers and marine biologists, the eye lens of a vertebrate possesses a remarkable structural quirk ($\text{Smithsonian Ocean, Key Methods of Aging}$). The center of the lens—known as the embryonic nucleus—is formed while the animal is still in the womb. Once formed, this central tissue becomes metabolically inactive. New cellular layers continue to wrap around the exterior throughout the animal's life, but the proteins locked inside the very core remain completely unchanged from the day the creature was born.
By extracting crystalline proteins from the eye lenses of 28 deceased Greenland sharks (which had tragically perished as accidental bycatch in commercial fisheries), the research team applied carbon-14 isotope analysis ($\text{Nielsen et al., 2016}$). This method leveraged a unique historical marker: the "bomb pulse" caused by atmospheric thermonuclear weapons testing during the mid-20th century, which drastically elevated carbon-14 levels across the global oceans.