This article first appeared in Issue 18 of our digital magazine CURIOUS.
In 2011, a UK survey asked the public a simple question: would you like to live forever? More than five out of every six people said no.
Turn it around, though, and the opposite is equally off-putting: do you want to die?
Perhaps that’s why we’re seeing more resources than ever before invested in life-prolonging science – from billionaires’ “blood boys” to the diets and lifestyles of the so-called “blue zones”.
And it seems to be working! As a species, humans are living longer than ever before, with life expectancy in rich nations such as the UK having more or less doubled over the past 150 years, and the number of individuals reaching their 100th birthday shooting up from about 95,000 in 1990 to a projected 25 million in 2100.
But how far can this go? Are we destined to always peter out at around the century mark, or can we increase the maximum human lifespan to, say, 150? How about 200?
What if there’s no limit at all?
Touch of grey
Creaky knees; an aching back; an increasingly hazy memory of where you left your keys – we tend to think of these as classic signs of aging. But that’s not quite right. According to the simplest scientific definition, such as it exists, those bodily foibles aren’t the result of aging – they literally are what aging is.
“Age and aging are not the same thing,” explains the Max Planck Institute for Biology of Ageing. “Age is just a number and is often subjective. Aging, on the other hand, is an observable process that can be described and defined scientifically. In aging research, aging is defined as a progressive loss of physiological integrity leading to functional impairment and an increased likelihood of death.”
Why we age, therefore, is a question of what causes this degeneration – and it’s here that the simple answer suddenly becomes incredibly complex. Aging, as far as we know, is the result of quite a few different, yet interconnected, factors: some nature, some nurture; some controllable, and others the product of random chance – plus some we don’t even know about yet.
Take food, for example. Intuitively, you might think that ready access to food would increase your lifespan – it’s hard to live to 100 if you starve to death aged nine, after all. But the reality is weirder than that: “It’s widely known that calorie-restricted diets can prolong lifespan,” wrote Charalampos Rallis, a Lecturer in Cellular Ageing at the University of Essex. “Short-term studies suggest that it also improves health in humans.”
Similarly, a life lived in comfort may be shorter than one with a little strife. It’s not as nonsensical as it may sound: “When food is plentiful and stress levels low, these genes make hay while the Sun shines by supporting growth and reproduction,” explained Alison Woollard, Associate Professor in the University of Oxford’s Department of Biochemistry. “But under difficult conditions, they take a ‘things can only get better’ attitude – their activities change, sparking a whole physiological shift towards cell protection and maintenance.”
You see, while growth and reproduction may sound like a positive thing, what it mainly is – especially once you’ve finished maturing – is a waste of resources. Translation, the process by which cells build new proteins and divide, is energy-consuming and limited: after a while, a cell will become senescent, or unable to divide any further.
How quickly this limit is reached certainly seems to be linked to one’s longevity. “The cells of a Galapagos turtle divide approximately 110 times before senescing,” notes biomedical researcher Avi Roy, “whereas mice cells become senescent within 15 divisions.”
Stand and deliver: Your money or your life
They say only two things in life are certain: death and taxes. If you’re rich, however, you can get around both – at least, that’s what the world’s most moneyed have always hoped.
In the past, the quest for eternal youth would have your Cleopatras and your Caesars reaching for bathtubs full of donkey milk and using face masks of crocodile dung. Today – well, things aren’t much better.
Case in point: the US tech billionaire Bryan Johnson. He spends, on average, $2 million per year on purported anti-aging technologies, claiming that his body now “accumulates aging damage… less than the average 1-year-old.” Which, if true, must be comforting, since his regimen has included weekly acid peels, starving himself for 23 hours per day, and using his own son as a portable blood bank – Elizabeth Bathory, eat your heart out.
But “there are no proven clinical benefits” of plasma or blood infusions on age-related diseases, writes Rachael Jefferson-Buchanan, Lecturer in Human Movement Studies (Health and PE) and Creative Arts, Charles Sturt University.
“Many of Johnson’s age-reversal methods are questionable, involve dodgy science, and have known side effects,” she said.
So, what can we do to eke out a few extra years on Earth? The answer is simple and, we hate to say, disappointing: “For the general population, watching your weight, not smoking, drinking moderately and eating at least five servings of fruit and vegetables a day can increase life expectancy by up to 14 years compared with someone who does none of these things,” writes Richard Faragher, University of Brighton Professor of Biogerontology, in an article with Nir Barzilai, Professor of Medicine and Genetics at Albert Einstein College of Medicine.
It may not be fun, but it is effective. “[The] difference exceeds that seen between the least and most deprived areas in the UK,” the pair point out.
In the end, though, super-longevity may come down to sheer dumb luck. “One study found that up to 60 percent of Ashkenazi Jewish centenarians have smoked heavily most of their lives,” Faragher and Barzilai note. “Half have been obese for the same period of time, less than half do even moderate exercise and under three percent are vegetarians.”
Who wants to live forever
So, there you have it: eat right, don’t smoke, and try not to let your cells get carried away on the protein building. But if it’s such a simple formula, can we say what the upper limit is on the outcome?
Well, it’s a tricky question to answer – amply proven by the fact that so many proposed “maximum human lifespans” have been blasted through in recent decades.
“In 1921 it was ‘demonstrated’ that ages above 105 were ‘impossible’,” writes Faragher. “Estimating the limits to longevity has since been criticized because every ‘maximum limit’ to lifespan so far proposed has been surpassed.”
Yet, despite all this successful aging, plus an ever-increasing population to boot, there’s one data point that’s remained constant for more than a quarter-century now: the age of the oldest human ever, Jeanne Calment, who died in 1997 at the frankly extraordinary 122 years and 164 days.
That figure is notably close to one commonly proposed limit on the human lifespan: about 120 years. And Madame Calment’s unbroken record isn’t the only reason for this figure’s popularity. “[If we] look at how our organs decline with age, and run that rate of decline against the age at which they stop working,” Faragher explains, “most calculations indicat[e] organs will only function until the average person is around 120 years old.”
Mathematical models have predicted a similar cut-off point. One 2016 study, for example, used demographic data to conclude that humans have a fixed maximum lifespan of about 125 years – and that the chances of any person reaching that age is less than one in 10,000. Other studies have produced extremely similar figures: 115, 124, 126, 130, and so on.
But some scientists are not so pessimistic. Breakthroughs in our understanding of the aging process have led to a hypothesized maximum lifespan of up to 150 years; for others, the sky’s the limit.
“We’re seeing death rates, among extreme ages, go down a little bit,” Ken Wachter, a professor of demography and statistics at the University of California, Berkeley, and lead researcher on a 2018 aging paper, told PBS at the time. “That means we’re not coming up against a limit to lifespan.”
Don’t fear the reaper
OK, so living off one hour of eating kale per day and milking your offspring for young blood doesn’t sound fun, but presumably it would be worth it – this is immortality we’re talking about, after all.
Unfortunately, the smart money’s probably on a limited lifespan. “I’m a little surprised that anyone today would question whether or not there is a limit,” S. Jay Olshansky, an expert on longevity and a professor in the School of Public Health at the University of Illinois at Chicago, told the New York Times Magazine.
“It doesn’t really matter whether there is a plateau of mortality or not in extreme old age,” he argued. “There are so few people that make it up there, and the risk of death at that point is so high, that most people aren’t going to live much beyond the limits we see today.”
Sure, there are plenty of proposed “cures” to aging and death: research has shown, for instance, that removing senescent cells from mice can improve their health and lifespan; improvements in machine learning have made artificial intelligence (AI)-discovered anti-aging drugs a realistic possibility; clinical trials abound in an attempt to target hallmarks of aging such as stem cell supply and cell communication. But for Olshansky, attempting to live forever is akin to trying to run a two-minute mile: “The human body is incapable of moving that fast based on anatomical limitations,” he said. “The same thing applies to human longevity.”
And perhaps, in the end, that’s not such a bad thing. Society moves on – and so, to our detriment, do our bodies. Our lifespans may be longer than ever before, but those extra final years are invariably still spent lonely, frail, and increasingly tired of life.
“Do we really want to live longer and longer?” asked Joris Deelen, a molecular epidemiologist at the Max Planck Institute for Biology of Aging, in an interview with the journal Erstrebenswert.
“As a scientist, I don’t aim for people to live to be 130 or 140 years old,” he said. “What is much more important is that they stay healthy for longer and we can delay the onset of age-related diseases or, ideally, prevent them altogether.”
CURIOUS magazine is a digital magazine from IFLScience featuring interviews, experts, deep dives, fun facts, news, book excerpts, and much more. Issue 21 is out now.
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