This question came to mind after I read a 2013 news story about Ming. It is a clam from Iceland that was estimated to be 507 years old, which earned it the title of the longest-living animal on the planet.
The clam was named after the dynasty that ruled China in 1499, the year in which its birth was calculated by carbon-14 dating and counting the layers of the interior of its shell. Because, similar to trees that form rings each year by growing, the Bivalvia deposit a new layer on their shell. Unfortunately, Ming passed away during transport to the laboratory where it was to be studied.
For comparison, the oldest human being was a French woman named Jeanne Calment, who lived just over 122 years. This lady’s age falls short of the life span of Jonathan, a tortoise who lived between 187 and 188 years. In turn, the oldest mammal, a bowhead whale, surpassed that record, by living up to 211 years. Moreover, according to researchers at Australia’s national science agency, genome sequence revealed that bowhead whales’ maximum lifespan can be up to 268 years!
But the Ming clam is a baby compared to the oldest known individual tree. The oldest known living specimen is an unnamed tree, which location is kept secret, but it is somewhere in the White Mountains of California. The tree was sampled in the 1950s but its age, 5,067 years, was not determined until laboratory work was completed in 2012. Before that, the oldest known tree was the “Methuselah” tree, 4,789 years old. Its age was verified by crossdating. Meaning it was seeded when we humans were inventing cuneiform writing. The three oldest trees in the world belong to this same species and, to protect the two that are still alive, both their photos and their exact location remain secret.
The longevity of clonal plants
To be honest, I thought that this question cannot be developed any further. But the information that I have been gathering while trying to answer it has revealed to me a planet earth I didn’t know existed. It is actually full of centuries-old or even millennial organisms, which use different survival techniques to reach extreme ages.
It turns out that, for some organisms, the 5,000 years of the long-lived pine are not a big deal. Although they exceed this number by playing a little dirty: they clone themselves.
These clonal trees live in colonies made up of genetically identical individuals descended from the same ancestor who have never reproduced sexually. An example of this case is Pando, a colony of populus Quaking aspens composed of 47,000 individuals that share the same root system.
Originally this forest began from a single tree. A genetically identical stem emerged from its roots and, in turn, it took roots from which more identical copies emerged. In other words, the organism itself is a gigantic root from which 47,000 copies of the same tree grow, each with a life expectancy of between 40 and 150 years.
The root system does not care if one of its stems dries out, or even that a fire burns half of them, since it always has clones that will continue to absorb the sunlight necessary to allow its survival. No one can deny that this survival method works. This tree (actually, this root system, but for all practical purposes it’s the same) has lived this way for 80,000 years.
But the life-span limit of clonal organisms does not stop there.
It turns out that a group of Australian researchers took DNA samples from 40 meadows of a seagrass species that is endemic to the Mediterranean Sea (Posidonia oceanica) along 3,200 kilometers. During the investigation, they found genetically identical algae separated by distances of up to 15 kilometers, which is why they concluded that there are entire posidonia meadows made up of endless copies of the same organism that, like the Pando tree, clones itself to spread its roots. The researchers speculate that some of these clone colonies could be between 80,000 and 200,000 years old, although this is a theoretical limit because some areas where it is found could be above sea level between 10,000 and 80,000 years ago.
These algae can expand to form large patches up to 16 kilometers long and weigh 6,000 tons together. By occupying such extensive areas, they guarantee their continuity if one of the areas they occupy runs out of resources. There are more species of clonic plants, but so far none have been recorded to be older than Posidonia oceanica. That does not mean that there are no organisms that live longer.
How about ancient bacteria?
Taking samples from the Siberian permafrost, a team of planetary biologists looked for organisms that live in the most hostile conditions on our planet to get an idea of where they could find living beings on other worlds. And they found something unusual: living Siberian actinobacteria that are between 400,000 and 600,000 years old. These actinobacteria would be, this time, the oldest living beings on the planet.
Well that’s it, right? The list ends here.
Not exactly. If we talk about ancient organisms, we could include bacteria that were revived after 25 to 40 million years spent inside the abdomen of bees preserved in amber. After being revived, the bacteria grew and their DNA was analyzed, finding their kinship with a current bacterium.
Although it was announced in 2001 that bacteria trapped in salt crystals had been revived after 250 million years, the results of this research are not considered entirely reliable.
Are there immortal animals?
But human intervention is not necessary to bring organisms that have been trapped in time back to life, as some can naturally remain dormant for long periods and wake up when conditions are better. Small animals called tardigrades, better known as water bears, can remain in a suspended state for hundreds or thousands of years. Dormant or not, the 600,000 years of actinobacteria are still a short period of time compared to immortality.
Yes, yes, in theory there are animals that have the potential to live forever. Here things start to get weird.
The clams of which I spoke at the beginning belong to the select club of organisms that present negligible senescence, which means that they do not develop apparent signs of aging as time passes and both their reproductive capacities and their physical form remain constant throughout their entire life. What is even weirder, their mortality rates do not increase with age. In other words, the youngest individuals of these species die with the same frequency as the oldest.
Theoretically, these animals could live indefinitely until they fell prey to a predator or died of an injury or infected by a virus.
One group of animals that possesses this superpower is lobsters, which are believed to frequently reach over 100 years of age (apparently, it’s hard to measure the age of a lobster). George’s impressive age, a 140-year-old lobster with an impressive weight of almost 10 kilos of weight, served as an excuse for not being cooked.
Other animals with negligible senescence include some species of turtle, a few fish, plants and bacteria, as well as worms. The clonal organisms that we discussed earlier also fall into this group, because they also have the potential to continue living until an external factor kills them.
Well, hold on to your pants because there is still the most extreme case to talk about: that of the famous immortal jellyfish. The jellyfish Turritopsis dohrnii begins its life as a polyp. It is a phase in the life cycle of some jellyfish which alternates with a medusoid phase.
Once they have reached maturity and have reproduced, these jellyfish are able to reverse their growth and return to the polyp phase through cell transdifferentiation, a process that allows cells to become other cells.
The head of the jellyfish turns around, its tentacles are sucked in, and it anchors itself to some substrate to grow and become a productive adult again. The jellyfish can repeat this process indefinitely, making it biologically immortal. A pity that, at 4.5 millimeters in diameter, it is an easy prey for predators.