Can We Live Forever?

Cell undergoing mitosis. IMAGE CREDIT: https://www.technologynetworks.com/tn/lists/10-things-we-didnt-know-last-week-14-september-2018-309567

The simple answer is not no, but rather that we don’t know. I think it’s safe to say that stories of Greek Gods and teen vampires who have been around for centuries are probably a stretch from reality, but we might not be giving our own human longevity enough credit. As recently as 2018, scientists have begun redefining human mortality, and in doing so, they are shaking the foundation of biological theories that have governed human lifespan for decades.

In 1965, Leonard Hayflick from the Winstair Institute in Philadelphia decided to take a look under his microscope to observe how cells divide. In doing so, he discovered a new mechanism involved in mitosis: telomere shortening. Essentially, Hayflick noticed that the telomeres of chromosomes became shorter with every cell division cycle, ultimately limiting it to 40–60 divisions before the cell “committed suicide” or underwent apoptosis. This revelation seemed perfect for explaining human aging to scientists using the Hayflick limit (as it would come to be known) to hypothesize a maximum human lifespan.

The Hayflick Limit illustration: With every cycle, telomeres shorten until mitosis eventually stops. IMAGE CREDIT: https://www.quora.com/Is-the-Hayflick-limit-the-real-reason-for-human-aging

Around the same time, medical professionals began exploring the volumetric flow of oxygen (VO2) to the heart muscle as a function of time. They concluded that the oxygen flow to the heart decreases with age. Thus, researchers postulated a maximum age beyond which the heart cannot receive adequate oxygen, ultimately leading to death. These studies, as well as those that have indicated greater probabilities of DNA damage with age, all point toward some kind of upper limit for human longevity. However, biological experimentation has not been the only testament to the fact that we may never reach the ranks of the “death-defying deities” that have embellished our movie plots and imaginations.

UN World Population Prospects demonstrate the steady increase of average lifespan since the 1950s. IMAGE CREDIT: https://en.wikipedia.org/wiki/Life_expectancy

A study in 2016, published in Nature, validated claims that the global average lifespan has seen a significant increase since the 1900s. However, these researchers from the Albert Einstein College also observed that such a trend was only true for people in a 70–100 age bracket. In other words, individuals with later birth dates experienced a greater probability of living only when within this range. Beyond 100 years, the study showed that survival rates plateaued, indicating that at some point, even improvements in health, medicine, and lifestyle cannot prevent death.

So, while all of this evidence seemed to suggest that we’ll never get to celebrate our 200-year birthdays, other scientists remained skeptical about this claim.

“If studies are accurate, that puts our maximum lifespan at about 115 years… If that’s the case, how do how do we explain Jeanne Clement whose 122-year life broke global records?”

Such were the questions of European researchers who embarked on a seven-year study of the centenarian population. From 2009 to 2015, these scientists observed the mortality rates of 3,836 individuals above the age of 105. Published in Science, the statistics conveyed that death risks did in fact increase with age. Interestingly, however, the risk of death for the sample remained stagnant as a function of time. This meant that a 105-year-old individual had the same risk of death (around 50%) as a 110-year-old in the sample. The implications of this study indicate that while is it extremely rare to reach 105 years, beyond that threshold, the odds of living are ultimately up to chance.

Now does that mean that, if the probability is in our favor, we can live indefinitely? The answer is NO. The study has only gone so far as to suggest some association between centenarian aging and a mortality plateau. The sample was also relatively small and limited to one region of the world. Furthermore, the study has not disproved any of the aforementioned theories that are still recognized as accurate factors in defining aging. Thus, the debate of human lifespan remains theoretical, backed on both sides both biological and statistical analyses.

One aspect of aging that is almost universally recognized by the scientific community is the impact of gender, health, and habits, all of which are crucial determinants in lifespan. For example, 87% of the women in the Science study were women, and on average, women have been 3–4 years older than their male counterparts at the time of death. Furthermore, certain genes have been linked to longevity, as have abstinence from smoking, balanced diets, and regular exercise.

Ultimately, the question of human lifespan remains one of the world’s greatest mysteries. Since the only thing we can guarantee is the present, let’s do our best to make it as innovative and exciting as possible! And who knows, we might just find that we have a few more candles to blow out on our cakes in the future :)

Works Cited

Dong, Xiao, et al. “Survival of the fittest: VO2max, a key predictor of longevity?” Nature, no. 358, 13 Oct. 2016, pp. 257–59. Nature, www.nature.com/articles/nature19793. Accessed 2 Nov. 2018.

“Italian study of centenarians suggests human lifespan may not yet have peaked.” The Local, 29 June 2018, www.thelocal.it/20180629/italian-study-of-centenarians-suggests-human-lifespan-may-not-yet-have-peaked. Accessed 2 Nov. 2018.

Roy, Avi. “Lust for life: breaking the 120-year barrier in human ageing.” The Conversation, 3 June 2013, theconversation.com/lust-for-life-breaking-the-120-year-barrier-in-human-ageing-14911. Accessed 2 Nov. 2018.

Strasser, B., and M. Burtscher. “Survival of the fittest: VO2max, a key predictor of longevity?” Frontiers in Bioscience, vol. 1, no. 23, 1 Mar. 2018, pp. 1505–16. US National Library of Medicine National Institutes of Health Search databaseSearch term Search, www.ncbi.nlm.nih.gov/pubmed/29293447. Accessed 2 Nov. 2018.

Prathysha Kothare

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