This shark's older than the Mayflower

There are sharks swimming in the North Atlantic today that were alive when Galileo was looking through his first telescope. The Greenland shark can live for at least 250 to 500 years.

They achieve this by living life in slow motion. They reside in waters so cold they hover near freezing, which slows their metabolism to a crawl. They grow only about one centimeter per year, meaning they don't even reach puberty until they are roughly 150 years old.

Finding their age is a macabre process. Because they don't have hard bones that grow rings like trees, scientists have to look into their eyes. The proteins in the center of their eye lenses are formed at birth and never change. By carbon-dating these core proteins, researchers discovered individuals that likely saw the 17th century.

These sharks spend centuries in total darkness with hearts that beat only once every twelve seconds. Most of them are also nearly blind due to a specific parasite that attaches to their corneas, though they don't seem to mind.

Because they move so slowly, they were once thought to be scavengers, but they have been found with entire seals in their stomachs-none of which showed bite marks, suggesting the sharks swallow them whole while the seals are sleeping.