Is there a limit to human life?

This article was first published in issue 18 of the digital magazine “CURIOUS”.

A 2011 British survey asked the public a simple question: “Do you want to live forever?” More than 5 out of 6 people answered “No.”

But on the flip side, the opposite is just as unpleasant. “Do you want to die?”

Perhaps that’s why we’re seeing more resources than ever being invested in life extension science, from billionaire “blood boys” to so-called “blue zone” diets and lifestyles. maybe.

And it seems to be working! As a species, humans are living longer than ever before, with life expectancy almost doubling in rich countries such as the UK over the past 150 years, with around 90,000 people reaching their 100th birthday compared to 1990. The number has rapidly increased from 5,000 to the present. It is predicted that by 2100 there will be 25 million people.

But how far can this go? Are we always destined to expire after his 100th century, or can he extend the maximum human lifespan to, say, 150 years?

What if there are no restrictions at all?

touch of gray

Creaking knees. Back pain. An increasingly fuzzy memory of where you put your keys – we tend to think of these as classic signs of aging. But that’s not entirely correct. By the simplest scientific definition that exists, these body weaknesses are not a result of aging, but literally aging itself.

“Age and aging are not the same thing,” explains the Max Planck Institute for the Biology of Aging. “Age is just a number and is often subjective. Aging, on the other hand, is an observable process that can be explained and defined scientifically. In aging research, aging is defined as the possibility of impairment and death. It is defined as a progressive loss of physiological integrity leading to an increase in

Therefore, the question of why we age is the question of what is the cause of this degeneration. And this is where the simple answer suddenly becomes incredibly complex. As far as we know, aging is the result of several different but interrelated factors. Some things are controllable, while others are the product of random chance. In addition, there are some things that we are not even aware of yet.

Take food, for example. Intuitively, you might think that having more readily available food would prolong lifespans. If you starve to death at the age of nine, it is difficult to live to be 100 years old. But the reality is stranger than that. “It is widely known that calorie-restricted diets can extend lifespan,” writes Charampos Laris, lecturer in cellular senescence at the University of Essex. “Short-term studies suggest it also improves human health.”

Similarly, a life lived in comfort may be shorter than a life lived with some conflict. “When food is plentiful and stress levels are low, and the sun is shining, these genes support growth and reproduction and make hay,” explains Associate Professor Alison Woolard from Oxford University’s Department of Chemistry. “But under difficult circumstances, they adopt the attitude that things can only get better. Their activity changes, triggering whole-body physiological changes geared toward protecting and maintaining cells.”

As you know, growing and reproducing may sound like a positive thing, but it’s mainly a waste of resources, especially after you’ve finished growing. Translation, the process by which cells build new proteins and divide, consumes energy and has limits. After a while, cells become senescent or can no longer divide.

How quickly this limit is reached certainly seems to be related to longevity. “Galapagos turtle cells divide about 110 times before aging, whereas mouse cells age within 15 divisions,” notes biomedical researcher Avi Roy.

Stand up and deliver: Money or life?

They say the only two things in life are certain: death and taxes. But if you’re wealthy, you can avoid both. At least, that’s what the world’s richest people always hope.

Once upon a time, Cleopatra and Caesar, in pursuit of eternal youth, would reach into bathtubs full of donkey milk and use face masks made of crocodile feces. Today, well, things are not so good.

A great example is American tech billionaire Brian Johnson. He spends an average of $2 million a year on what he calls anti-aging technologies, and claims his body has “accumulated age damage…less than the average his year old.” Masu. It must be comforting if this is true, since his regimen included weekly acid peels, fasting for 23 hours a day, and using his own son as a portable blood bank. Elizabeth Bathory, please be patient.

However, Rachel Jefferson Buchanan, a lecturer in human movement research (health and physical education) and creative arts at Charles Sturt University, says that “the clinical benefits of plasma or blood infusions for age-related diseases are unproven.” It has not been done.”

“Many of Mr Johnson’s age-reversal methods are questionable, involve questionable science and have known side effects,” she says.

So what can we do to survive a few more years on Earth? The answer is simple, and I don’t want to say sorry, but for the general population, watch your weight, stop smoking, Drinking moderate amounts of alcohol and eating at least five servings of fruit and vegetables a day can add up to 14 years to your life expectancy compared to the rest of the population,” said Richard Farragher, professor of biogerontology at the University of Brighton. In an article with Nir Barzilai, professor of medicine and genetics at Albert Einstein College of Medicine, he writes:

It may not be fun, but it’s effective. “[The] The differences exceed those seen between the most deprived and least deprived areas of the UK,” they said.

But in the end, super longevity may come down to pure dumb luck. “One study found that up to 60 percent of Ashkenazi Jewish centenarians smoked heavily for most of their lives,” Faragher and Barzilai note. “Half have been obese for the same period of time, less than half are even moderately active, and less than 3% are vegetarian.”

Those who want to live forever

Eat right, don’t smoke, and don’t let your cells go crazy building protein. But with a formula this simple, can we say what the upper bound of the result will be?

Well, this is a difficult question to answer, but this is amply evidenced by the fact that so many “maximum human lifespan” proposals have been ignored in recent decades.

“In 1921, it was ‘demonstrated’ that an age greater than 105 was ‘impossible,'” Faragher writes. “Estimating lifespan limits has since been criticized, as all previously proposed ‘maximum limits’ to lifespan have been exceeded.”

But despite this steady aging of the population and continued population growth, there is one data point that has remained constant for more than a quarter of a century. That’s the age of Jeanne Calment, the oldest person in human history. A frankly extraordinary 122 years and 164 days.

This number is particularly close to one of the commonly proposed limits for human lifespan, approximately 120 years. And Madame Carment’s timeless record isn’t the only reason for this figure’s popularity. “[If we] We look at how our organs decline as we age and compare the rate of decline to the age at which our organs stop working,” Faragher explains.[e] The organs do not function until the average person is about 120 years old. ”

Mathematical models predict similar cutoff points. For example, one 2016 study used demographic data to find that the maximum human lifespan is pegged at approximately 125 years, and that a person’s chance of reaching that age is less than 1 in 10,000 of her age. I conclude that there is. Other studies have found very similar numbers, such as 115, 124, 126, and 130.

But some scientists are not so pessimistic. Breakthroughs in understanding the aging process have led to the hypothesis that maximum lifespan is up to 150 years. For others, there are no limits.

Ken Wachter, a professor of demography at the University of California, Berkeley and principal investigator on a 2018 paper on aging, told PBS at the time that “mortality rates in the extreme age groups are gradually decreasing.” Ta. . “That means we’re not facing the limits of lifespan.”

Don’t be afraid of the Grim Reaper

Yeah, it’s not fun to survive by eating kale for an hour a day and milking the young blood of your offspring, but it’s probably worth it. Because this is immortality we are talking about.

Unfortunately, smart money probably has a limited lifespan. “I’m a little surprised that there are people today who question whether there is a limit,” S. Jay Olshansky, a longevity expert and professor at the University of Illinois at Chicago’s School of Public Health, told the News. Ta. York Times Magazine.

“Whether there is a plateau in mortality in very old age is not very important,” he argued. “Very few people will ever get there, and the risk of death at that point is so high that most people won’t be able to live much beyond today’s limits.”

Indeed, there are many proposed “cures” for aging and death. For example, studies have shown that removing senescent cells from mice improves their health and longevity. Advances in machine learning have made anti-aging drugs discovered through artificial intelligence (AI) a real possibility. Many clinical trials are underway targeting features of aging, such as stem cell supply and cell communication. But for Olshansky, trying to live forever is like trying to run a 2-minute mile. “Based on anatomical limitations, the human body can’t move that fast,” he says. “The same thing applies to the human lifespan.”

And perhaps it’s not such a bad thing after all. As society advances, our bodies suffer as well. We may live longer than ever before, but those extra final years will still be spent alone, frail, and increasingly weary of life.

“Do we really want to live longer?” asked Joris Diehlen, a molecular epidemiologist at the Max Planck Institute for the Biology of Aging, in an interview with the magazine Elstrevenswerd.

“As a scientist, I don’t aim for people to live to 130 or 140,” he said. “Far more importantly, they can stay healthy for longer, delaying the onset of age-related diseases, or ideally preventing them altogether.”

CURIOUS Magazine is IFLScience’s digital magazine featuring interviews, experts, in-depth information, fun facts, news, book excerpts, and more. Issue 21 has been published.