"I think it's reasonable to suppose that one could oscillate between being biologically 20 and biologically 25 indefinitely." -- Aubrey de Grey

Time may indeed be on your side. If you can just last another quarter century.

By then, people will start lives that could last 1,000 years or more. Our human genomes will be modified to include the genetic material of microorganisms that live in the soil, enabling us to break down the junk proteins that our cells amass over time and which they can't digest on their own. People will have the option of looking and feeling the way they did at 20 for the rest of their lives, or opt for an older look if they get bored. Of course, everyone will be required to go in for age rejuvenation therapy once every decade or so, but that will be a small price to pay for near-immortality.

This may sound like science fiction, but Aubrey de Grey thinks this could be our reality in as little as 25 years. Other scientists caution that it is far from clear whether and for how long science can stall the inevitable.

De Grey, a Cambridge University researcher, heads the Strategies for Engineered Negligible Senescence (SENS) project, in which he has defined seven causes of aging, all of which he thinks can be dealt with. (Senescence is scientific jargon for aging.)

De Grey also runs the Methuselah Mouse prize for breakthroughs in extended aging in mice. The purse of the M Prize, as it is called, recently grew beyond $1 million.

LiveScience recently spoke with de Gray about his idea of living longer, and perhaps forever.

LiveScience: What is your definition of aging?

Aubrey de Grey: The definition that I like is not very good if you want to cover all species, but it's pretty good if you want to do something about it. I define aging as the set of accumulated side effects from metabolism that eventually kills us.

Is your goal to just extend the human lifespan substantially or to enable us to live forever?

I don't see any inherent limit to how long it would be desirable to live. If life is fun at the moment, because one is healthy and youthful, both mentally and physically, then one is not likely to want to die in the next year or two. And if a year or two down the road, life is still fun because one is still youthful and so on, then the same will apply, and I can't see a time when that would cease to be true.

When did you first come up with idea for your SENS project?

Well, I've always considered aging to be undesirable, but I didn't begin to consider that I could make a contribution until about ten years ago. I suppose the major breakthrough was when I came up with the scheme that I now describe as SENS, and that happened about four years ago.

What happened was that I was gradually learning a lot of biology because my wife is a biologist. I was originally trained as a computer scientist, and I regarded aging as obviously undesirable but not my problem, that someone else would be working on it.

But the more biology I learned, the more I also learned about biologist and about the attitudes toward working on the biology of aging that biologists tended to have, and basically, I wasn't very impressed. I found that rather few biologists were interested in the problem at all, and I thought, "Well, that isn't very good,", so I thought I'd see what I could do.

Your background is in computer science. How does that qualify you to spearhead a project on aging?

My background is enormously beneficial. There are really very important differences between the type of creativity involved in being a basic scientist and being an engineer. It means that I'm able to think in very different ways and come up with approaches to things that are different from the way a basic scientist might think.

Could you give me an example of when your background has proven useful?

Well, I suppose that the whole SENS project is one big example. What I've done there is I've identified a set of things to fix, a set of aspects of aging that we have some respectable chance to repair, and I've realized that if we can do all of these things reasonably well, then we're done.

Basically, we'll have made the age related problems that we suffer from these days no longer an inevitable consequence of being alive. What I've done is basically factored out all the complicated details of how metabolism causes these things in the first place. It will be many decades before we understand the way cells and organs work well enough to be able to describe in detail the mechanism of how these problems actually occur.

But my way of thinking is that we don't need to know the details of how they happen. So long as we know what these things are that do happen, we can figure out ways to fix them. This is counter to the ways that scientists think, because scientists are interested in knowledge for its own sake, whereas I'm interested in knowledge as a means to an end.

Could you give me a timeline for how you envision your project succeeding?

The first part of the project is to get really impressive results in mice. The reason that's important is because mice are sufficiently furry and people can identify with them. If we get really impressive results in mice, then people will believe that it's possible to do it in humans, whereas if you double the lifespan of a fruit fly, people aren't going to be terribly interested.

Now, what I want to do in mice is not only develop interventions which extend their healthy lifespan by a substantial amount, but moreover, to do so when the mouse is already in middle age. This is very important, because if you do things to the mouse's genes before the mouse is even conceived, then people who are alive can't really identify with that.

I reckon it will be about 10 years before we can achieve the degree of life extension with late onset interventions that will be necessary to prove to society's satisfaction that this is feasible. It could be longer, but I think that so long as the funding is there, then it should be about 10 years.

Step two will involve translating that technology to humans. And because that's further in the future, it's much more speculative about how long that's going to take. But I think we have a fifty-fifty chance of doing it within about 15 years from the point where we get results with the mice. So 25 years from now.

What do you think about the idea that with so much life at stake, people would be less willing to take risks?

I used to be more pessimistic about this than I am now. Five or six years ago I wrote a book in which I predicted that driving would be outlawed because it would be too dangerous to other people, but now I think that what's actually going to happen is that we'll just throw money at the problem. Rather than simply avoiding activities that are risky, we'll make them less risky through technology. For example, it's perfectly possible already to build cars that are much safer than those which most people currently drive, and it's also possible to build cars that are safer for pedestrians--with auto sensors and auto braking to stop from hitting a kid running out in the road and things like that.

It's just a matter of priorities. When there isn't that many years of life to lose, the priority isn't there to spend the money. It's all a matter of weighing out the probabilities.

Once the technology is available, nearly everyone is going to want it. Of course, there's going to be a minority of people who think it's better to live more naturally in some way or other. We have parallels like that in society today, like the Amish for example.

Some would say that death is a part of life. What would be your response to those people?

Death will still be a part of life when we haven't got aging anymore. If you mean that some people would say that aging is a part of life--well, that's certainly true, but a couple hundred years ago tuberculosis was a part of life, and we didn't have much hesitation in making that no longer a part of life when we found out how.

What do you say to critics who think that this money could be better spent towards curing diseases like cancer?

This is a very important point. Because we're going be in a situation where we can extend lifespans indefinitely, this argument doesn't work. If it were a case of simply having a prospect of extending our healthy lives by 20 or 30 years, then one could legitimately argue that this would be money more ethically spent on extending the lifespan of people who have a below average lifespan. But when we're talking about extending lifespans indefinitely, I don't think that really works. The other thing to bear in mind, is that it's not an either or thing. The reasons why people in Africa for example, have a low life expectancy is not just because of medical care, but also because of political problems.

What kind of life will the immortal or nearly-immortal lead? Will they have to be on a special diet, or have constant organ transplants?

Like any technology, when it first starts off, it will be a bit shaky, a bit risky, it will be very laborious and expensive and so on, but there will be enormous market pressures that will result in progressive refinement and improvement to the technology so that it not only becomes more effective, it becomes more convenient and so on. This will be an example of that.

In a very general sort of sense, one could probably think in terms of having to go in for a refresh every 10 years or so. Exactly what would be involved in that will change over the years. It might start off as lets say a month in the hospital, and 10 years down the road, that will turn into a day in the hospital.

A good parallel is vaccines. For example, when we take a holiday in Africa or Southeast Asia or whatever, we get a shot to make sure that we don't get malaria. And that's all we have to do, and when we get there we can eat Mc Donald's as much as one likes.

So you think it'll one day be as easy as getting a vaccine?

Yes, that's right. A lot of these things, even in the early stages will amount to vaccines and drugs. Though of course, there will also be a lot of gene therapy and stem cell therapy and much more high tech stuff.

Why did you establish both an institute and a prize?

I think it's very important to have this two-prong approach. The idea here is that we don't really know what's going to work, but we have a fair idea of approaches that have a good probability of working.

If you look at past technological achievements, some of them succeeded by just throwing serious effort and serious resources at the problem, and people were pretty sure of what they had to do to make the thing work. The Manhattan Project is a fine example of that. Everyone basically knew how to build the atomic bomb, it was just a question of working out the kinks.

Then we've got things where there were loads of different possibilities about how the thing might be done, and it was important to motivate people and give incentives. For example, when Lindbergh flew across the Atlantic, that won a prize. And when someone invented a chronometer that worked properly at sea, that won a prize. Things like that. That was where you wanted to give incentives for people to follow their hunches, because it wasn't very clear which approach was going to work.

I think that when we're talking about life extension, we're sort of halfway between these two situations. We have a bunch of ideas which one can make a good case that it's going to work, but we also want to hedge our bets, and let people follow their hunches as well.

Of your seven SENS targets, which do you consider to be the most important?

It's not possible to say. I don't think we will be able to achieve more than a relatively modest amount of life extension, if any, until we can get at least five or so of these things working, and we might need to do all seven before we get more than a decade of life extension.

Why do you personally want to live forever?

It's not really a matter of living forever, it's just a matter of not wanting to die. One doesn't live forever all in one go, one lives forever one year at a time. It's just a case of "Well, life seems to be fun, and I don't see any prospect of it ceasing to be fun unless I get frail and miserable and start declining." So if I can avoid declining, I'll stay with it really.

What would you do if you could live substantially longer?

They say variety is the spice of life, so I don't think I would do the same things every day. I'd like to be able to spend more time reading, and listen to music, and all that sort of thing, things that I never get to do at all at the moment.

You think this project is going to succeed in your lifetime?

I think it's got a respectable chance. I'm definitely not relying on it. My main motivation comes from the thought of how many lives will be saved.

Your strategy would involve not only preventing aging, but reversing it as well. Does that mean people will get to choose what age they want to remain?

Absolutely. So the idea is that we wouldn't be eliminating aging from the body. It'll be a case of going in periodically and having the accumulated damage repaired. So exactly what biological age you actually have at any point is really just a question of how often you go in for rejuvenations and how thorough they are.

So the more treatments you undergo, the younger you can be?

That's right. I think it's reasonable to suppose that one could oscillate between being biologically 20 and biologically 25 indefinitely.

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7 Deadly SENS

Nuclear Mutations/Epimutations These are changes to the DNA, the molecule that contains our genetic information, or to proteins which bind to the DNA. Certain mutations can lead to cancer.

Mitochondrial Mutations Mitochondria are components in our cells that are important for energy production. They contain their own genetic material, and mutations to their DNA can affect a cell's ability to function properly.

Intracellular Junk Our cells are constantly breaking down proteins that are no longer useful or which can be harmful. Those proteins which can't be digested simply accumulate as junk inside our cells.

Extracellular Junk Harmful junk protein can also accumulate outside of our cells. The amyloid plaque seen in the brains of Alzheimer's patients is one example.

Cell Loss Some of the cells in our bodies cannot be replaced, or can only be replaced very slowly.

Cell Senescence This is a phenomenon where the cells are no longer able to divide. They may also do other things that they're not supposed to, like secreting proteins that could be harmful.

Extracellular Crosslinks: Cells are held together by special linking proteins. When too many cross-links form between cells in a tissue, the tissue can lose its elasticity and cause problems.

The Oldest People

Those who have lived the longest in modern times, in years and days, according to estimates in some cases: