Physically strong people live longer

aging : "It would be a waste to live forever"

Mr. Kirkwood, I am 28 years old now. How long will i live

It would be arrogant to try to answer that. Your family history is important to this, your lifestyle, the changes in society. But you have a good chance of turning 90, even 95. With luck, you could even make it to 100.

With luck or with good genes?

You need both. Chance plays a big role. But when you get very, very old, you most likely have genes that drive that longevity. That's why people like me look for longevity genes either in centenarians or at least in people who are 90 years old.

Is there a certain age from which genes are crucial?

There is no genetic clock for aging. Chance plays a big role. You can see this very clearly with certain worms: We can breed populations of genetically absolutely identical worms and stir them in liquid culture so that all worms have exactly the same living conditions. These worms have an extremely precise development program. Each adult animal produces exactly 959 body cells. And there is a mutation in these worms that makes them live longer. But if you then take two populations, one long-lived, one short-lived, each genetically identical, the life span of an individual is still immensely variable. So even with these worms, which have such a precisely regulated development and which have a strong genetic influence on aging, you cannot predict the life span from the genes. The same goes for people.

You are 59 years old. Does research get more personal as you get older?

Not really. The thing that frustrates me the most is what aging does to the sense of sight. I've been wearing glasses since I was ten. But now I have three glasses. Glasses for driving, glasses for my desk when I read publications. And these glasses that are bifocal. I find it really annoying to keep track of things. On the other hand, aging is an interesting journey. You loosen up, I actually enjoy life more. You have a different view of life, things are more interesting, entertaining, funnier.

What do you do to get old?

I am trying to eat healthy. But I don't avoid things either. I like to eat steak and fries, but not every night. I eat a lot of vegetables and a lot of fish. But that's also the kind of food I like. I don't live an optimal lifestyle for a long life. Because I have too much pressure and stress; i am ambitious and driven. Try to be more relaxed. I am learning to take life easier, and the older I get the better I get at it.

What should I do to improve my chances of turning 100?

You should love your body and treat it like a person who loves their car, treats it, polishes it and all those things. Fuel yourself, exercise, get enough sleep, feel good. Self-esteem is very important to good health. Try to stay interested. Keep the desire to live a full life. Keep asking questions!

According to studies, I should get married too, right?

Existing studies show that marriage extends life. But it should be a happy marriage if possible. And it probably doesn't make any difference whether you're getting married or in a committed relationship. Having a healthy relationship with another person, being able to share frustration, is good. Studies have only compared married people and singles.

Aristotle believed that every sexual intercourse reduced the lifespan. Does abstinence also prolong life?

This probably only applies to female fruit flies. Apparently the males also inject substances with their sperm that harm the females. These are supposed to damage the sperm of rivals. The opposite is true for humans. Probably, sex increases life expectancy because it is physical exertion and good for mental health. Having children doesn't necessarily shorten life either. There is a study from Norway that shows that the life expectancy of women with a large number of children is decreasing. But that's eight or more children. And it's not that amazing, because we know that pregnancy is not good for a woman's bones and teeth because the calcium is diverted for the growing embryo.

But women who get particularly old are more often childless?

There is a relationship between fertility and life expectancy in humans. This is probably due to the immune system. Having a very sensitive immune system increases your chances of getting old in this world of infectious diseases. In a woman, however, this can also reduce fertility, because in order to allow a fertilized egg to mature in the body, the immune system has to make a compromise, so to speak. So a woman may live longer but cannot have children because her immune system is particularly sharp.

200 years ago it was believed that all living things would have to die at some point because otherwise the offspring would have no chance of asserting themselves. That's a nice idea.

It makes sense: If living beings did not age, then the world would be full of animals that take up space and eat everything and there would be no room for growth, no possibility for new generations to arise. This is a really nice idea, but like so many great ideas, it is fundamentally wrong. This shows a simple fact: In nature, animals do not live long enough to age. Only humans have an overpopulation problem. Animals in the wild die young. If you keep mice in the laboratory, they live three years, maybe even four years. But 90 percent of mice do not experience their first birthday in nature. It is very unusual for a mouse to live to be 18 months in the wild. So nature does not need a death mechanism to prevent overpopulation.

But there are also animals that live very long?

However, there are animals that live very long. But they don't live long enough to show signs of aging. In some animals, a small part may get old enough to get old. But these are just exceptions, so few that aging is not needed as a population control mechanism.

Then why do some animals live longer than others?

What an organism does in its lifetime is this: it takes in food, turns it into energy, and then uses it to do the things it needs to do in life. And what does he have to do? It has to grow, produce offspring, and maintain and repair its body because it is constantly being damaged. So the question is: how much energy should a living being put into this repair? The answer: Only enough energy to keep the body in good condition for the time the living being is believed to survive in the wild. So the practical limit for a mouse is 18 months. The mouse needs a body that is in good shape for 18 months. Anything beyond that would be a waste. That is the "disposable soma theory" that I put forward in 1977.

So we are aging because we are living longer than our body expected?

Humans age because the enormous pressure of natural selection has created organisms that only put as much energy into their repair mechanisms as is necessary to survive the expected lifetime. Investing in a body that can live forever would be a waste.

For nature, yes, but many people would certainly like to invest there. Will there ever be a pill to buy that will make us live much longer?

It is possible, but probably not in our lifetime. Some pharmaceutical companies have invested a lot of money there. But I believe that the human body puts a lot of energy into the repair mechanisms anyway. There may not be that much room left to improve.

But theoretically we could influence the body in such a way that it puts more energy into the repair mechanisms?

That would be conceivable. We are now, for the first time in human history, freed from the danger of starvation in the countries of the first world. In countries like Germany and Great Britain, hunger was still ubiquitous 200 years ago. Even nobles suffered from it, as studies of their skeletons show. Humans could not store food for a long time and therefore there were always famines. Today we have all the energy we need. Some of that could perhaps be put into the repair mechanisms.

Would that make sense?

Living longer is naturally tempting. Certainly better than the alternative. But we're gaining two years of life expectancy every decade. Did we manage that successfully? No, we adapt terribly badly.

And still dream of eternal life.

A book about aging was published in the United States some time ago. The thesis was: If aging research advances so quickly that we gain more than a year of life expectancy every year, then we have reached the speed of flight. The book was a call to force this so that we are not one of the last generations to die. I thought that was terribly nasty.

Why bad?

Think about how this is perceived by people who actually grapple with the realities of getting older. You surrender to a fantasy that distracts from the real problems. We have to use the advances in aging research to improve the quality of life in recent years.

What actually needs to be repaired?

There have been opposing gangs in the field of aging research for years. One says: aging is caused by DNA damage, and another gang says: No, this is all due to damage to the mitochondria, the power plants of the cell. And then there is another group that says: No, no, no, it's about proteins that clump together with age. But the logic of the disposable soma theory says: a single mechanism is nonsense. Presumably all possible damage will accumulate.

What if the body doesn't fix it?

The body can destroy defective cells by sending them to suicide. Or they just stop dividing. Destroying the cell is arguably the safest alternative, but as we get older all cells are damaged. If the body destroyed them, we would quickly disappear. We would just shrink to nothing. On the other hand, such cells shouldn't divide any further, because then they can degenerate and tumors develop. So they just snap into place. Like locking it in a room, locking it and throwing the key away. This is aging.


When you have too many cells that are in this retirement age, it becomes difficult to maintain that cell count. You can imagine it like with the TÜV. The body is like the inspector who examines the car and says: there are errors, the car must no longer be driven. The only difference is that a car that can no longer be driven no longer makes any sense. However, a cell that no longer divides can still perform important functions.

The interview was conducted by Kai Kupferschmidt.

Tom Kirkwood (59) researches aging. He studied mathematics and biology at Oxford and Cambridge and has been director of the Institute for Aging and Health in Newcastle since 1999.

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