How Long Can Humans Live? Seven Theories and a Quiz

You might think that you have heard everything there is to know about how long humans can live, but even in this overworked corner of human research, there is always something new.

Over the last few decades. we have watched in awe as longevity statistics have exploded. For people in industrialized countries, life expectancy, at the beginning of the 20th century, was between 30 and 45 years, rising steadily to about 67 years by the end of the century. Life expectancy continues to rise until now, people who live to age 100 or older are the fastest growing demographic. In the past, researchers have looked to improvements in health care, nutrition, and standard of living to explain why some people live significantly longer than others. Other researchers have redirected their attention to the habits of super-centenarians, or the detection of ‘blue zone’ areas of the world in which people live to an exceptional age.

Looking for the secrets of aging in the living cell

Meanwhile an army of scientists have been investigating longevity at the cellular level. It’s here, they believe, in the study of the composition and behavior of the human cell, that they will find the causes of life and death. It now seems possible to understand the very foundation of life, and get a glimpse into the secrets of what makes humans age.

Although postponing death raises important ethical and practical questions about global overpopulation and considers the existential dilemma of immortality, the secrets of human aging is irresistible to researchers. Theories about how and why human cells age, and how we can fight it, appeal to us, and whenever new ideas emerge, we pay attention. Recently, a word new to many of us, has found its way into our consciousness.

The word is senescence, defined as the cause of death when billions of our cells stop growing, dividing and replicating themselves. The potential for the future of medicine in understanding senescence is not lost on the medical and pharmaceutical community. Dr. van Deuten of the Mayo Clinic, in an article written by Megan Forliti, makes this observation:

“Senescent cells that accumulate with aging are largely bad, do bad things to your organs and tissues, and therefore shorten your life but also the healthy phase of your life. And since you can eliminate the cells without negative side effects, it seems like therapies that will mimic our findings – or our genetic model that we used to eliminate the cells – that drugs or other compounds that can eliminate senescent cells would be useful for therapies against age-related disabilities or diseases or conditions.”

The many theories of cellular stress

Various theories exist, one idea being that telomeres, the repeated segments of DNA that occur at the end of chromosomes come to the end of their genetically programmed number of repeats, and can divide no further, causing the cell to die. There are others:

The Wear and Tear Theory, assuming that cells simply wear out. Cross-linking Theory, assuming that the structure and shape of the cells change so that they are unable to carry out their functions. Autoimmune Theory, assuming that immune reactions begin to attack cells of the individual’s own body.

There is also the Oxidative Theory, the Free Radical Theory, and the Mitochondrial Theory. This latest theory seems the most complex, and is based on the idea that a vicious cycle exists within the mitochondria (an organelle in the cytoplasm of cells, containing material and enzymes important for cell metabolism), in which:

“the mutation of mitochondrial DNA impairs the function of proteins in the organelle’s respiration machinery, thereby enhancing the production of DNA-damaging oxygen radicals, which ultimately, after several other stages, leads to tissue dysfunction and degeneration”.

And lastly, the Molecular Inflammatory Theory, which addresses age-related inflammation of tissues in the body, and has been linked to many age-associated illnesses, including cancer, cardiovascular disease, arthritis, and several other diseases.

Many of these theories have been aired in the public domain, making their way into television shows and publications, with claims that some medical treatment, some supplement or other, can fight cell damage and thereby extend longevity.

And a theory that has yet to be revealed

Because living longer, and delaying death has so much universal appeal, I wasn’t surprised to find the following notice about an emerging theory on extending the human lifespan. It was presented by Dr. George Tetz of the Human Microbiology Institute at the American Society for Microbiology in New York last summer:

“Based on Tetz’s theory and law, we propose a novel model to calculate several parameters, including the rate of aging (or the rate of reduction of the remainder of the maximum permissible level of alteration) and the remaining lifespan of individuals. We believe that this theory has great explanatory and predictive potential for the influences of diseases, medication, and medical procedures on human longevity.”

They go on to say, “We would be happy to share all the details of this theoretical concept right after its official publication (in press).” Having explored innumerable theories of cell longevity, I have an open mind, and will, as the authors suggest, await publication of Dr. Tetz’s discovery.

But, it’s important to note, just the same, that there are no known medical treatments or advancements that can affect the length of human life expectancy. Only time will tell what the future holds.

Meanwhile, if you are curious about how long you will live, and don’t mind a less scientific approach, here is a short quiz for you. Be aware, however, that the results are non-binding!

You can take the Quiz here:

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30 Responses to How Long Can Humans Live? Seven Theories and a Quiz

  1. Wow! What a fascinating post! I have never before seen all these theories in one place–so clearly and succinctly explained. I admire your research skills and clarity of presentation. There’s a lot to think about. I find that my doctor has used most of these theories at one time or another to explain something to me, but she never indicated that the theories are incompatible. You can’t use them all!

    • Still the Lucky Few says:

      That’s probably true, Dr. Rin. Each seems to have a separate thesis behind it. I admire scientists—they can be exact and creative at the same time!

  2. This post gives so much interesting information. I wonder how these theories will affect longevity for our grandchildren? Meanwhile, I’ll accept the analysis of the quiz and make every remaining day count!

    • Still the Lucky Few says:

      I think that life expectancy will continue to go up as we learn more and more about how new scientific knowledge can benefit our health. But I do pay attention to the genetic theory that says that there is a finite number of years to the human life span. But, of course, we simply do not know right now.

  3. I agree with the idea, “You only live once, and if you work it right once is enough.” So far it’s working for me. I lead a healthy lifestyle and what will be will be.

    • Still the Lucky Few says:

      I agree, Jean. And the happier we are with what we are given, the more satisfying our lives will be.

      • I’m in agreement with CM – I try my best to keep “topside”, I’m not keen to take the quiz, as I’ve taken them before and once or twice, apparently I’m already dead! So take them with a grain of salt. As for the studies, well whatever (note that CM) rocks your boat…

        • Still the Lucky Few says:

          Glad you didn’t take the quiz seriously—it made no claims about being accurate! The studies, however, are a different matter. Some of them make every effort to offer a clear picture of a particular thesis. A big study takes a great deal of work and dedication (and money!) so they are usually approached in a sincere and careful manner.

          • I get the feeling that you think I was belittling your research and post…that wasn’t my intention. My thoughts on much of the scientific studies if that yes it takes “dedication and money” but often it is refuted by the very next person.

            I have an illness that has evaded the medical profession to come up with any sort of real helpmate…. between 1989 – 2017 there have or are in situ – 136 PhD thesis underway. The thesis will be covering anything from finding a “marker, test, cure, and so forth” – to date nothing practical has been shown to completely help. People do get better…but often the toll of the whole “thing” means life never returns to what they deemed normal.

            I’m classed as “moderate” on the spectrum, but in recent months, I realised that “the better I had been” is “sliding downwards” – but to self managing as best as I’m able…

          • Still the Lucky Few says:

            No, not at all, Cathy. As you might have noticed, I am happy to accept all comments, and never take offence. Research is not the “end game”, after all, and is only a path to learning more about an issue. Illnesses that can’t be solved are a terrible strain on anyone—hopefully you will have some answers soon. And it sounds as if ‘self-managing’ is working for you.

        • okay I got more curious on the quiz…I’ve apparently got a quite a few more years left to muck around doing, more or less what I like..

  4. Fascinating post, but I’ll pass on the quiz. I’ll just take what comes 🙂

  5. Rummuser says:

    Longevity is celebrated in my culture too but there is no great desire to live long. Our most common blessing to younger people is to wish them their allotted life span. I personally do not want to live so long as to be a burden on myself and / or others. Having been a caregiver for a father who suffered and gave suffering to some others during his last years, I do not want to do that to either me or to my son. He was 95 when he died.

    I recite a Sanskrit prayer regularly that simply asks for a trouble free (for self and others) death and poverty free life. This prayer does not ask for a long life.

    • Still the Lucky Few says:

      As you say, a long life is not always desirable. I think quality, as with everything else, is more important. As for me, I want both—but above all, a long life in good health! Thanks for your always wise comment!

  6. Barry Dym says:

    Thanks for much for this wonderful tour of current research.

  7. hillsmom says:

    Well, I didn’t know I was already dead. Greetings from the “Wrinkle Farm/Storage Bin” where there are more like me, and a DH who is a generation older than I. Was it Nicole Hollander’s Sylvia who said that she’d live to slip off a bar stool (in Harry’s Bar) into that sweet goodnight? Sounds like a plan. =^..^=

  8. Clive says:

    A very interesting piece, Diane, though I have to admit that some of the science went a little over my head! And the quiz gave me another 14 years to live – considerably worse than my parents. I think I need some lifestyle changes!

    • Still the Lucky Few says:

      Well, genetics counts more than a sketchy questionnaire, so you should go with that! Good to hear from you, Clive!

  9. DJan says:

    This was a lot of fun, both to read about the ideas of human longevity, and taking the test. According to them, I’ve got fifteen years left. Hope they are right, and that they are productive years! Thanks for all the info. 🙂

  10. Hi Diane! Great stuff. I too love to research about longevity but I hadn’t heard about these theories before today. You’ll have to let us know when that need study is published. Meanwhile, I’m in the camp for “quality not quantity.” As long as I am reasonably active, able to enjoy my life, and add some small contribution to others, then I’m happy to be alive. ~Kathy

    • Still the Lucky Few says:

      Lovely to hear from you, Kathy. I love research, and enjoyed writing this. I will keep my eye on the new study, and continue this thread when I know. I find that our online community is committed to contributing to others—and that’s so wonderful!

  11. Maddy says:

    Well the quiz said I won’t last past 90 but I fully expect to live to 100 and if I do I am going to have a cigarette!

  12. Cathi says:

    This is fascinating! Glad I met you through “the cow who jumped over the moon.” I’m a new follower. Cathi

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