People get older, as conditions of life, medical treatment and knowledge of sciences improves. But the funny thing is, although the average age of the overall population increases, the peak of highest reachable age did not shift, if we can believe history, at all.
Of course, you don’t have to be an atheist to not believe that biblical Methusalem did most probably not reach the announced age of 969 years, but considering his appearance in the Hebrew Bible, it shows that people always were intrigued by the idea of high age, or even more so by the idea of immortality.
While immortality is yet a too far reaching concept to really grasp with the sheer endless lists on the perks and perils of such immortality, historically the idea is very well reflected in myths about the Holy Grail or alchemists search for the “philosopher’s stone”.
Not surprisingly, it also became a field of interesting research in modern science as well.
Nature is filled with curious things regarding aging and delaying or outsmarting mortality.
A Tasmanian plant called King’s Lomatia is estimated to be around 43.000 years old. While the individual plants lifespan is capped around 300 years, every “offspring” or remaining part of the plant is genetically identical. Because of a triploid chromosome set, which makes it sterile, the plant cannot reproduce, thus it guarantees survival by cloning itself over and over again, making it effectively ageless.
Even more elaborate, at least when it comes to strangeness, is Turritopsis dohrnii, also called the “immortal jellyfish”.
This species of jellyfish undergoes a transformation back to polyp state, from which it can regrow again into the adult jellyfish. As of now, only one Japanese scientist from Kyoto University was able to keep his jellyfish colony alive over almost two years, and he reported that they rebirthed themselves ten times within this timespan. If you wonder how these jellyfish die in nature, it’s rather simple. They depend on a special diet, are susceptible to disease and have a lot of predators hunting for them. Because of this, although possibly immortal, it’s rare to find jellyfish in the wild living for longer than very few years.
And finally, there are of course bacteria, which can restart metabolism even after hundreds of thousand years, practically being “resurrected”, revived out of stasis back to activity, as makes its appearance every now and then in the media when researchers yet again revive another “iced” sub-Antarctica bacteria.
Amazingly so, it is very hard to find vertebrates, or mammals for that matter, that live beyond a certain lifespan. The oldest living animals are seaborne, the gigantic bowhead whale and the Galapagos turtle competing in the domain of above 200-year-olds. However, 200 years is far ridiculous compared to the other, non-animal competitors, still making animals very susceptible to time and ultimately death. Regarding humans, some individuals have been proven to reach the age of 120, however, the club of super-centenarians is still very exclusive compared to the overall population.
Apparently, evolution made a hard call and put a rather strict timer on all living animals, where else it can turn a blind eye to the occasional plant or bacteria.
So why has evolution created such a stringent timespan for our lives? For biologists, this is a rather easy question and can be answered with a fundamental principle which is true for all existence. Balance.
Since animals live in a complex ecosystem of predators, limited food supply and diseases, life spawn rarely comes into play, as the overall population falls prey to one of the former mentioned decimators. Lifespan is more like a fail-safe mechanism of nature to ensure that when everything else falls short, population size is still limited by time, although realistically, something else gets the best off you before time does.
In the rare case that one population outsmarts their environmental boundaries and becomes the dominant species, the top of the food-chain, then aging and death act as a safety switch ensuring the survival of the ecosystem.
So how does aging happen?
Interestingly, science has troubles answering this rather easy question; since our cells permanently regenerate within hours to days, why can that not go on indefinitely? Two prominent explanatory models have been proposed;
Reduction of telomere-length on our DNA and the accumulation of genetic damage over time leading to apoptosis. Funnily enough, these principles have been discovered by investigating the 2nd most common form of death in the western world: cancer
Cancer cells are immortal, a phenomenon discovered by investigation of HeLa cells, a cell line derived and named after Henrietta Lacks, a patient who died from cervical carcinoma. Taken in 1951, these cells are still dividing and proliferation, mocking the Hayflick Limit of 40–60 cell division events of normal cells. Under investigation they divulged their secret; they had a hyperactive telomerase enzyme, a protein responsible for extending the end of our DNA with random base pairs, otherwise our genetic information would shorten every time after DNA replication occurred as the DNA polymerases cannot duplicate the very last ends of DNA. Usually, telomerases extend just a little piece of DNA which is used up after 40–60 division events and the cell becomes senescent, but in HeLa cells, these proteins are efficient enough to counteract this aging effect, immortalizing themselves.
So why not introduce this hyperactive telomerases into all our cells to get immortal as human? The problem is, that we, as a living organism, are flawed. Being not perfectly constructed gave us the freedom to undergo evolution over time, however, this follows the principles of survival of the fittest as a species, not on a singular level. In our case, the flaws we accumulate over time lead to our destruction, either through apoptosis or dysfunction leading to necrosis. If we accumulate more and more mutations, if our repair mechanisms are not working 100% of the time, it is not hard to understand, that sooner or later, some damage we accumulated will be too much to handle, leading to organ failure and death.
So is immortality, or at least long and healthy methusaletic life, just science-fiction?
Maybe today. Maybe tomorrow. But not necessarily in the future.
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