Published in Vice, 2016
In August this year a team of marine biologists came up with an ingenious method of radiocarbon dating sharks in Greenland. Doing so, they found one female specimen was 400 years old. She was a five-metre shark, probably born sometime around the death of Queen Elizabeth 1.
While the discovery made for some heady news releases, and excited anyone in the field of radiocarbon dating, it also raised a pretty serious question. That is, how do some animals live for so long, while others—like humans—only get a few decades?
To understand, we'll need to get a little technical. The concept of senescence refers to biological ageing. The precise mechanism behind human senescence is very complicated; however, it's fair to say we experience the progression of ageing differently to many other species. Theoretically, some animals will never die of natural causes.
Negligible senescence is basically defined by a lack of ageing, the absence of functional decline. Such a phenomenon explains some seriously long lifespans, such as the alleged 255-year-old Aldabra giant tortoise, which died in 2006 at India's Kolkata Zoo. Or the 507-year-old ocean quahog clam that was caught off the coast of Iceland in the same year.
So how are they living so long?
Dr Sarah Milton of Florida Atlantic University attributes negligible senescence to "adaptations that permit both extended anoxic survival and recovery." In other words, the ability to survive long periods without oxygen, as well as being able to recover rapidly from those periods. Both set organisms up for surprisingly long lives.
This definition doesn't include the extra biological time amassed by cases of suspended animation—such as the Tardigrade, otherwise known as That Water Bear everybody loses their shit over. Tardigrade have relatively short lifespans but can theoretically exist forever based on their ability to take biological timeouts, which is cheating.