Science | Why do we die?
I could tell you a hundred ways an organism can die, but it is much more difficult to explain why we are programmed to do so. We spend billions globally to divert and delay death, however it gets all of us in the end, whether it is disease, injury or senescence (natural aging). We are currently winning some of the battles against mortality. Our advances in medicine, hygiene and preventative methods have ignited excitement that the first person to live to 150 years may have already been born, zealous anti-aging evangelist Audrey de Grey considers the first 1000 years olds to be born within 10 years of them.
However, not all of life is bound to the same constrains as humans, whilst we are forced to wither over time, due to the mutation of our DNA, decrease of cell numbers and the inefficiencies of protein cross linkages, some cells are able to form mutinies and break from the orthodoxy.
In 1951 Henrietta Lacks died from an extremely virulent strain of cervical cancer (aged 35) her cancer was so virulent in fact that it is still with us, strewn across the globe in labs and worth billions in research dollars. There is in fact three times her cancer than there ever was of her, her cancer is immortal!
Normal cells are usually bound to the Hayflick limit, 40-60 replications before apoptosis (programed cell death). No matter the nutrient content or how sterile the medium the cells are contained in, all perish within a set period. DNA within cells are capped by telomeres, repetitive (non-coding) DNA, that is slightly shortened by the replication process. Each clipping reduces the telomeres length and is eventually stripped causing the coding DNA to become damaged by the process leading to apoptosis.
Conversely our DNA contains the remedy to this limiting longevity. We code for telomerase, the protein that builds and extends the cap. This function is utilised in utero, resetting the offspring’s bio-clock, returning youth to the aged cells of the parents. Such a finding have led to excitable claims of taking telomerase supplements to maintain our youth, conversely telomerase outside of reproduction is strongly correlated to cancer, Henritta Lacks’ cancer maintaining very active telomerase during each cell division.
This poses the question to why haven’t we evolved to control the switch of longevity we all code for, why haven’t we been pushed to live for a millennia, rebuilding our DNA caps along the way? It’s all because of sex. Sex is probably the most difficult obstacle to immorality. We are walking gonads, with a sole function to inseminate and produce, selfishly dictated by our genes. Living in a precarious world of disastrous change and interims of tranquillity, sexual reproduction combats these changes my mixing our genes (traits) with others to find the most adapt assortment for the environment. One admixture of genetic material may prosper in the current times however, 100 years later and after great change your prosperous genes are now detrimental. Sex increases variation to spread your bets on the environment variation in later generations. All this sex causes increased completion, predation and disease, becoming incredibly detrimental to the health of the organism. Death then appears to be a handicap hypothesis to our competitive relationship with the world that encapsulates us. Death is a compromise, the medium of enabling our DNA to live forever at the cost of the body.
Those that defy death
The Immortal Jelly Fish (Turritopsis nutricula)
Known as transdifferentiation the jelly fish is the only known animal capable of completely reverting back to it’s child like form under stress full conditions. The process hasn’t been observed throughly however it is thought this process could go on ad infinitum, declaring it immortal.
Water Bear (Tardigrada)
The most polyextremophile of the animal kingdom, they can survive the most apocalyptic of conditions. Boiled in oil and frozen in liquid nitrogen (below -265°C) the animal will persevere. They have been shot up into space, subjected to devastating ionising radiation and solar winds, and even dehydrated for 10 years and yes it has survived! But what is even more remarkable is these critters aren’t found only on the top of volcanoes or deep sea trenches, but everywhere, even in Leeds.