Like the elves of Middle-earth, some species on Earth don’t die of old age. The scientific term is negligible senescence, which means they show little or no signs of biological aging. It applies when scientists don’t find the expected lower reproductive ability and increased risk of death that comes with increasing age. Like Tolkien’s elves, these species can die but they don’t just because they’re old. Could these animals be immortal and live forever? It could be that we mortal humans just haven’t been studying them long enough to see the pattern.
Turtles and tortoises live long lives but they do eventually reach a point of biological mortality. Alligators and crocodiles are often thought to be immortal because they continue to grow and have babies their entire lives. While reptiles are certainly weird and ancient, long-term research shows they do in fact age. But the jury is still out on these other species.
The Immortal Jellyfish
The species literally named the immortal jellyfish may be just that. They begin life as free-swimming larvae and then attach to the seafloor as polyps. They mature into a medusa, or what we think of as a typical jellyfish, with a bell and tentacles. The immortal jellyfish, and a few other known species, can reverse this metamorphosis. If stressed by environmental changes or injury, adults can revert back to the polyp stage and start over again from there. Scientists recently sequenced its genome and found that it has duplicate copies of genes that repair DNA, allowing it to avoid the weaknesses of old age.
We already know that Greenland sharks can live to be over 500 years old. And they’re still living their best lives with no end in sight. They are also one of the largest sharks because they continue to grow over the centuries. Scientists think they live mostly in the cold ocean depths, which may help them grow more slowly and live longer. Their whole lives are on an extended timeline. Greenland sharks don’t sexually mature until they are 150 years old. And females gestate their pups for years before giving birth. At this point, we have no idea how long Greenland sharks are capable of living.
Naked Mole Rats
Most rodents of a similar size to naked mole rats live about six years. But they can live at least 30 years. And that’s just as long as we’ve been doing research on their lifespans, so it’s possible they live much longer. Recent studies of the naked mole rat suggest its ability to survive in low oxygen environments could be the reason it lives far longer than any other rodent. And they still remain fertile at that advanced age. We simply don’t know how long they can live.
Trees like aspen are clonal, meaning an entire grove is technically one organism. There’s a root system in Utah thought to be more than 80,000 years old. Though the trees only survive about 150 years, they live on through others. Seagrass in Australia recently declared the world’s largest organism is also a clone. And estimated to be 4,500 years old. Some bacteria and yeast, as well as some species of flatworms that divide in order to reproduce, also live on indefinitely in this way.
Other Real World Creatures and Plants That Live Forever
A form of hibernation allows some species, like tardigrades, to live indefinitely. Organisms that shut down biological activity under cold or low oxygen conditions can come back to life. There are also species that live an epically long time. We may never know if they are indeed immortal simply because we can’t study them on such a long time scale. There are bristlecone pine trees known to be over 5,000 years old. Which is essentially as long as the history of humans making scientific observations.
Rivers and oceans hold many mysteries, including long-living species of fish. Some rockfish live to be at least 250 years old. Lobsters continue to grow throughout their lives. This ability could be linked to their ability to repair DNA. A type of clam called an ocean quahog can live at least 500 years.
So while there’s little hope of humans becoming immortal like the elves in The Lord of the Rings, it’s fascinating to know that other life on Earth can. And it doesn’t stop scientists from trying to learn their secrets. One lifetime for us is just the blink of an eye to an aspen grove, after all. Perhaps even elves age, but no one else on Middle-earth has been around long enough to see it happen. The fact that the oldest elf in Tolkien’s saga, Círdan the Shipwright, was eventually able to grow a beard indicates biological changes even after thousands of years.
Featured Image: Natural World Facts
Melissa is Nerdist’s science & technology staff writer. She also moderates “science of” panels at conventions and co-hosts Star Warsologies, a podcast about science and Star Wars. Follow her on Twitter @melissatruth.