What will happen when we all live to be over a hundred?

Let's consider what will happen when it becomes normal for human beings to surpass the 100-year mark. We're talking about when, not if, because we can already assume that yes, sooner or later we will reach this point. We're already heading toward a future where aging will be treatable. It will no longer be considered inevitable, but we will be able to do something to improve it, slow it down, halt it, or even reverse it.

The work being done in laboratories to understand and halt the aging process first involves defining what aging means, exactly. It's a slow, progressive process of tissue degeneration. But what exactly does this "degradation" mean?

The major discoveries in this field date back to the beginning of the century, when a revolution in understanding the molecular and cellular mechanisms of aging took place. However, the search for a solution to understanding aging dates back much further. In fact, in the earliest surviving literary work, Poem by Guilgameix, tells the story of a king of Uruk who, around the year 2000 BC, dedicated himself to the pursuit of immortality. In other words, the person who wrote the first work of fiction already reflected what has been and will be one of humanity's greatest aspirations: to conquer aging.

Aging, in and of itself, might not be so problematic if it weren't for the fact that, as the body loses functionality, it also develops health problems, which trigger various diseases. In other words, the probability of dying increases exponentially after the age of sixty or seventy. Why? What makes us, after a certain age, much more prone to illness and much more sensitive to death? This is the real key to aging, and finding a solution involves trying to understand it at the molecular, genetic, and cellular levels.

Until now, we've defined aging as degeneration, a loss of bodily functions. This change is easy to see externally, but if we could travel inside the body and observe our organs, we would see that they also change in appearance over time. And if we looked even closer, we would see that the cells that form them are also different: there is a proportion of cells that is not the same; the composition of these tissues has changed. And this is where it starts to get interesting, because at other levels we can't act, but with cells we can. Cells can be studied, extracted, inserted, changed, eliminated, or even manipulated.

Cellular aging

Since the end of the last century and the beginning of this one, we have been discovering a series of processes that have led us to define what has been called the twelve causes of agingThis recipe that scientists have proposed to explain why we age from a biological perspective is also a roadmap. If we believe that aging is caused by these twelve factors, what we must do to stop it is treat them. The more we understand these processes, the more potential targets for future treatments we discover.

Several of these factors that lead to aging end up generating what we know as senescent cells. Basically, they are old cells that don't function as they should. The current hypothesis is that we age because we accumulate old cells, because we have more and more senescent cells. To a certain extent, this makes sense: it's easy to understand that, as cells age, so do the body's tissues. Why is this important? Because we now know where we can attack, what problem we need to solve: we need to eliminate senescent cells.

These cells are colloquially known as zombie cells, because they are neither alive nor dead; not only do they not do their job, but they also bother their neighbors and, like zombies, can turn other nearby cells into zombies. In short: we must kill zombies. But how? In a 2011 study, they managed to eliminate these cells in mice, and found that they lived longer. It was the first biological demonstration in an animal that proved that eliminating senescent cells can be good for health and may be a way to improve aging. Following variations of this recipe, in several laboratories around the world we have managed to extend the lifespan of mice by nearly 30%. We have obviously not achieved immortality, but we have significantly slowed the biological process of aging and everything that entails. In humans, it is more complicated, so we cannot yet administer the drugs we use with mice, but we hope that one day we will. If these senescent cells are truly what cause aging, eliminating them completely or largely could make us rejuvenate.

We're living longer and longer. Life expectancy is increasing, but one thing isn't: the years we spend in good health. In other words, we're living longer, but not better. The years gained are often bad years, lived with chronic illnesses. What we would like is healthy aging, extending the years of youth, not those of old age. This is what the science of aging pursues: not necessarily living longer, but living better. We are beginning to design drugs and other treatments that lead us to believe that, one day, we will be able to slow or halt aging, and perhaps even reverse it in some cases.

But what would be the consequences of achieving this dream? If it really happened, if we scientists working on aging were to develop a pill that would allow us to live better and longer, what would happen next?

From pyramid to bell

The first imaginable problem is that we wouldn't fit on the planet. If we're no longer in a sustainable context now, imagine what would happen if we lived more than 100 years, or even if we didn't die. But perhaps this isn't exactly the problem. According to UN forecasts for the coming years, the trend is not upward but rather downward.

Throughout human history, population graphs have been shaped like a pyramid, with more young people than old people. But today's population is no longer like this, but rather like a cylinder. Births are falling, and the upper part is growing dramatically. People who reach ninety or ninety-five are no longer an insignificant minority: in 2019, they represented between 1% and 2%. Future forecasts are moving in the same direction. By 2050, 2075, or 2100, the pyramid is expected to progressively transform into a bell-shaped pyramid. If in the 1950s the percentage of people over sixty-five was 10%, it is estimated that in half a century it will be 70%. In other words, the majority of the population will be elderly. The problem is perhaps not that there isn't enough room for more people on the planet, but that not enough people are being born to compensate for the aging population. We may think this is a European problem, but continents like Africa and Asia, which until now provided youth to the older continents, are showing the same trend. Therefore, it seems we are heading, almost irreversibly, toward a progressive aging of the world's population.

So, to answer the initial question: what will happen when we all reach 100 years old? The first thing is that the entire planet will be aging, and there will be no working population to pay pensions or generate wealth in a country. If almost everyone is over 65, the situation will not be sustainable. As we said, there are forecasts indicating that up to 60-70% of the population could be above retirement age, an age that will obviously have to be readjusted if we head towards this scenario. Furthermore, life expectancy has changed radically in the last century. Initially, it was still 30 or 40 years in some places, and now it is over 80 in much of the world. Therefore, one of the conclusions—or one of the problems—we will have if we truly manage to promote longevity or slow aging is that humanity will be even older than it already is, with all the problems that entails.

We must ensure that, instead of the progressive degeneration that is common in most cases—and which involves many years of poor health and illness—everyone ages more slowly, and then, when the time comes and the body can't take it anymore, there is a sudden decline. In other words, we must not experience an aging process in which we endure poor health for 30 or 40 years, as often happens today. That's why we study people who have reached these extremes, such as supercentenarians, including Maria Branyas, who for a time was the oldest person in the world. Through these cases, we hope to better understand why, in some fortunate people, age-related degeneration is concentrated almost exclusively in the final stages of life, allowing them to reach very advanced ages in very good health. If we want to overcome the current limit of 120 years, if we want people to live longer and in better health, the only way to do so is with drugs or interventions targeting the biology of aging. We need to find this "healthy aging pill"; otherwise, we won't be able to get much further. It's not a certainty, but it is a possibility that science is beginning to put on the table.

Science fiction

But we can also mix science with science fiction and talk about even more extreme future possibilities. We've considered the possibility of prolonging aging, of perhaps creating a fountain of eternal youth, in which we can bathe and emerge rejuvenated. More than science fiction, we could call it speculation: pondering how far we can go with the limits that science offers us. Could it even offer us immortality?

In principle, on paper, immortality is biologically possible. There are animals, such as the hydra or some jellyfish, that constantly regenerate and never age. Without going that far, animals such as whales, some species of worms, or tardigrades also have tissues that degrade very slowly. Therefore, this slow aging, and at its extreme, immortality, already exists in nature. Can humans go that far? In this science fiction exercise, can we become immortal elves like those Tolkien imagined? This would be one of the most extreme questions in the field of aging, but science already allows us to think even further.

We've talked about drugs that can eliminate zombie cells and slow the degeneration that comes with aging. But we can go a step further and decide what the humans of the future should be like, beyond being practically immortal or aging very slowly. Because we can now manipulate human genes. Dr. He Jiankui, for example, is a Chinese scientist who, in 2018, created the first genetically modified humans. In the same way that we have long modified animals and plants, Dr. Jiankui broke all current ethical standards and manipulated the genes of four girls before they were born in China. This opens a new path, another door into a realm that was once the stuff of science fiction and is now increasingly becoming real science, offering us a range of new possibilities for the future. If we can modify our genes, the rules of the game change radically.

However, it must be kept in mind that humanity's genetic variability is what makes it interesting. If we start manipulating genes, perhaps we'll all end up cut from the same cloth, identical. Or we could even go to the extreme that fiction has also proposed: an army with perfect soldiers, with genetically modified people that we would then clone as many times as we wanted, as seen in the saga of Star Wars. Today, for example, we already know which genes generate too much muscle, so we could modify a baby's gene before it is born to make it a stronger adult. In the film Star WarsFurthermore, they are more obedient. We still don't know the obedience gene, but we can't rule out identifying it one day. Thus, since the 2018 experiment, the possibility of redefining what life is, what existence is, or what being human is, has opened up by modifying this instruction book that is genetics.

In the end, imagination may be the only limit. Why can't we mix human genes with genes from other animals? So that, at birth, we're a hybrid of human and animal? Or go so far as to completely redefine humanity and make us all blue with white spots, if we so desire.

Obviously, this opens up a formidable ethical debate. Can we do this? Should we allow it? improve our species with chemical treatments. And we say improve as a new concept because science or medicine, until now, was dedicated to curing or preventing; but now we are talking about improve, which involves taking a completely healthy person and modifying them. But what does it mean? improveHow do we define what a improvementIt's very subjective. What may be a disability for one person may be their identity for another. We're entering a tricky area, where we use science and medicine to make changes that don't necessarily have to do with health. And this raises a whole new set of ethical challenges.

We also have another type of improvement on the table: mechanical ones. Until now, everything related to the concept of the cyborg—the fusion of human and machine—was limited, for example, to fitting prosthetics to people who had lost a limb. No one disputes that this is a good use of medicine. But what happens when, in the future, these limbs are better than the originals? Perhaps we'll end up looking for replacement parts, saying: "I don't like this arm, I want a mechanical one because I'll be a better tennis player, or I'll be able to work better, or lift more weight." And perhaps humans will end up being entirely robotic bodies with a biological brain. Then we wouldn't live a hundred years, we would live thousands, because we would simply replace body parts when they broke down. It's an even more efficient way of overcoming the biological degeneration we were talking about. Perhaps the future of humanity lies in this stage: finding replacement parts for biological parts that deteriorate. That's science fiction, because we still don't have enough knowledge of robotics or technology to create body parts that work better than the originals, but we're moving toward that scenario.

Where is all this leading us? What will humanity look like when we can all live a hundred years, when science gives us all these options? We've talked about the possibility of eventually becoming immortal like elves, or cyborgs, or—why not?—superhumans; or perhaps even the human species will look completely different: blue and eight feet tall. What's the limit? Which path will we choose?

Even though all this isn't possible yet, it's an increasingly present possibility, a possibility that forces us to ask ourselves what future we want for humanity. And, above all—and here comes the ethical aspect again—if this becomes possible, if we have a combination of genetics, drugs, robotics, or whatever, that allows us to do these things, improvements Of the human being, who will be able to pay for it? Who will be able to afford it? If we look at the history of science and medicine, we will see that any discovery starts out expensive and only accessible to a portion of the population. The most recent example is the COVID vaccines: here in Europe, we were getting our third dose, and in Africa, they hadn't even received their first. The distribution of the planet's resources is unequal; it always has been, and, unfortunately, it probably always will be. In this case, the problem is that we're no longer talking about vaccines: here we're talking about completely redefining humanity, which will have a much more profound impact. We could end up with a "two-speed" humanity: on the one hand, superhumans (or posthumans, as they're being called lately), who would be almost a new species, modified by science; and on the other, the rest of humanity, with the same old challenges: obesity, cardiovascular disease, dying from malaria and other infections, and all the health problems that we would continue to endure. If we don't use science properly, if we don't know how to identify its limits, we could end up in a dystopian future with this division of humanity. This change we're seeing now is unlike any previous step in evolution because, for the first time, this evolutionary leap isn't made by nature, it isn't made by natural selection, it's made by us.

Where does this lead us? If we believe in the doctrine of posthumanism, or transhumanism—the philosophical and scientific doctrine that says we should do everything in our power to use science to improve The human species—the proposal would be to continue advancing and improving our species in some way. But where is this race taking us? What is the end of this path we've only just begun?

That's why it's so important to discuss these issues now, while they're still an exercise in anticipation, in science fiction. But all of this will become a reality in the coming decades. We must begin to prepare society for these changes. What has always happened is that science makes a discovery before society has been able to decide if it really wants it. We've seen this with the example of genetic modification. In other words, before we, as a society, have decided whether or not we want to allow the genes of human embryos to be manipulated, we've already done so. This is the big problem: we're always one step behind science, and that's what we must fight against. All these debates, which may still seem distant to us, are very necessary. We must start talking about it now so that we're not caught off guard, especially at a time when, from across the ocean, we see this push to once again embrace extreme liberalism, in which everyone should be able to decide how they want their future or what they want to do with their body—if you can afford it and have the money. The European ethical tradition is very different. In Europe, we tend to ask ourselves what impact advances will have on society, what inequalities they might create, and whether or not state intervention is necessary. These are fundamental debates, and it seems that, for the moment, this liberalism is winning the day in much of the world.

Science and technology are never good or bad in and of themselves: it all depends on how we use them. Genetics and the advances we've discussed fall into that category. We can use them to radically change humanity and create a dystopian humanity and a more unequal and unhappy world, or we can use this technology for good. This depends entirely on us; it depends on how we are able to use these gifts that science offers us. Let us, therefore, be responsible.

Salvador Macip

He is a doctor, scientist, and writer, director of the Health Sciences Studies at the UOC, a researcher at the Barcelona Beta Brain Research Center, and professor of molecular medicine at the University of Leicester. He is the author of more than 40 books on science and fiction. The Final Conflict: What will happen when we all live to be over 100?, held on May 12, 2025, as part of the "Challenges of the Immediate Future" series, organized by the European School of Humanities and the Macaya Palace of La Caixa, Barcelona. The transcription and adaptation was by Ariadna Núñez and Salvador Macip. The Catalan translation was by Elena García Dalmau. This article was published in Spanish in issue 71 of La Maleta de Portbou magazine.