We've already tacked three decades onto the average lifespan of an American, so what's wrong with adding another few decades?

A centenarian riding his bike in Long Beach, California (Reuters).

So far as we know, the last hundred years have been the most radical period of life extension in all of human history. At the turn of the twentieth century, life expectancy for Americans was just over 49 years; by 2010, that number had risen to 78.5 years, mostly on account of improved sanitation and basic medicine. But life extension doesn't always increase our well-being, especially when all that's being extended is decrepitude. There's a reason that Ponce de Leon went searching for the fountain of youth---if it were the fountain of prolonged dementia and arthritis he may not have bothered.

Over the past twenty years, biologists have begun to set their sights on the aging process itself, in part by paying close attention to species like the American Lobster, which, despite living as long as fifty years, doesn't seem to age much at all. Though some of this research has shown promise, it's not as though we're on the brink of developing a magical youth potion. Because aging is so biologically complex, encompassing hundreds of different processes, it's unlikely that any one technique will add decades of youth to our lives. Rather, the best we can hope for is a slow, incremental lengthening of our "youth-span," the alert and active period of our lives.

Not everyone is thrilled by the prospect of radical life extension. As funding for anti-aging research has exploded, bioethicists have expressed alarm, reasoningthat extreme longevity could have disastrous social effects. Some argue that longer life spans will mean stiffer competition for resources, or a wider gap between rich and poor. Others insist that the aging process is important because it gives death a kind of time release effect, which eases us into accepting it. These concerns are well founded. Life spans of several hundred years are bound to be socially disruptive in one way or another; if we're headed in that direction, it's best to start teasing out the difficulties now.

But there is another, deeper argument against life extension---the argument from evolution. Its proponents suggest that we ought to avoid tinkering with any human trait borne of natural selection. Doing so, they argue, could have unforeseen consequences, especially given that natural selection has such a sterling engineering track record. If our bodies grow old and die, the thinking goes, then there must be a good reason, even if we don't understand it yet. Nonsense, says Bennett Foddy, a philosopher (and flash game developer!) from Oxford, who has written extensively about the ethics of life extension. "We think about aging as being a natural human trait, and it is natural, but it's not something that was selected for because it was beneficial to us." Foddy told me. "There is this misconception that everything evolution provides is beneficial to individuals and that's not correct."

Foddy has thought long and hard about the various objections to life extension and, for the most part, has found them wanting. This is our conversation about those objections, and about the exciting new biology of aging.

Foddy: The reason I present it that way, is that there's always this background moral objection in enhancement debates, where a technology is perceived to be new, and by virtue of being new, is depicted as threatening or even strange. That goes for everything from genetic engineering to steroids to cloning and on and on. I think it's always worth contextualizing these things in terms of the normal. So with human cloning it's worth remembering that it's exactly the same as twinning. With steroids, it's worth remembering that in many ways it's not that different from training and exercise, and also that people have been taking testosterone since ancient times. I think this way you can kind of resist the idea that something is wrong just because it's strange.

When you're talking about medicines that help us live longer, it's important to realize how much we've already accomplished. In the last 150 years or so, we've doubled our life span from 40 to 80 years, and that's primarily through the use of things you can characterize as being medical science. In some cases it's clear that we're talking about medical enhancement---vaccines, for instance, or surgical hygiene and sterilization. And then more broadly there are other, non-medical things like the sanitation of the water supply and the pasteurization of milk and cheese. All of these things have saved an enormous amount of life.

It used to be that people would die of an infectious disease; they'd be struck down when they were very young or when they were older and their immune system was weak. Now almost nobody in the first world dies of infectious disease; we've basically managed to completely eradicate infectious disease through medical science. If, at the outset of this process, you asked people if we should develop technologies that would make us live until we're 80 on average instead of until we're 40, people might have expressed these same kind of misgivings that you hear today. They might have said, "Oh no that would be way too long, that would be unnatural, let's not do that."

So, in a way, we shouldn't view it as being extremely strange to develop these medicines, but in another sense we're at a new stage now, because now we're at the forefront of having medicines that actually address the aging process. And that's what I'm interested in talking about---the kinds of medicines that actually slow down the aging process, or at least some of the mechanisms of aging.

Can you explain how senescence, the biological process of aging, is unevenly distributed across species?

Foddy: There are different animals that are affected differently by various processes of aging. In my paper I go into the case of the American Lobster, which lives about as long as a human being. When you dissect one of these lobsters at the end of its life, its body doesn't show much in the way of weakening or wasting like you see in a human body of advanced age. That suggests that aging can evolve differently in different species. Lobsters seem to have evolved an adaptation against the cellular lifespan. There's this phenomenon where the DNA in our cells basically unravel after they've divided a certain amount of times, but lobsters have this enzyme that helps them replenish their telomeres---the caps that hold DNA together.

That's one of the reasons why lobsters don't seem to undergo aging in the same way that we do. Other species give off an antioxidant chemical in their bodies that prevent these oxidizing free radicals in our bodies from breaking us down. That's why doctor's recommend that you have a certain amount of antioxidants---some species are really good at producing those naturally.

There is this idea that when you're evolving you make certain trade-offs. Lobsters and clams don't really move around a lot; their bodies move and grow very slowly and one of the upsides of that is that they've been able to invest their evolutionary chips, so to speak, in resisting the aging process. Human beings, on the other hand, have to move around quite a lot. We have giant brains and we have to be able to run away from saber tooth tigers. As a result we have bodies that burn a lot of calories, and so that's where our chips are invested. It's just a difference in our evolutionary environment and that's why we've evolved to live and die the way we do. But it could have easily not turned out that way---that's the point I really want to make.

What are the current biological limits on our human life span, or our human "youth span," as you call it---the time that we're able to live as young, vibrant, reproducing individuals?

Foddy: The sky is sort of the limit there. There won't be a magic pill that gives us infinite youth, but over time there will probably be different technologies that allow you a few extra years of youth. We think of aging as being a unitary thing, but it's made up of hundreds of different processes. So, one of the different things we think about, for example, is dementia, the state where your brain sort of wastes away. Now, if we discover a way of reversing that process, or slowing that process, that would be one dimension where we no longer age, where our minds will stay youthful for longer. It's also possible that we might be able to find a way of stopping people's muscles from wasting away as they get older.

Nothing is going to be super dramatic, but there will be a point where you'll look back a hundred years and notice that people used to get really kind of feeble and after awhile they weren't capable of really thinking or processing information anymore, and they had to go into a home and they had to be looked after and nursed for a time. And that will seem very old-fashioned and very barbaric, but I very much doubt it will happen at a moment in time where we suddenly realize that some magic pill has exponentially extended our youth. Part of that's because we're not exactly clear what aging is. We've identified a whole range of processes, but there ere still a whole lot of arguments in the scientific community about what is really responsible for aging, and which of the processes are subsidiary to other processes.

Have we glimpsed, even theoretically, ways that we might add to that youth-span. What are the bleeding edge technologies that might allow us to overcome aging?

Foddy: I'm not a scientist, so I don't want to weigh in too heavily on somebody's body of research. We've seen promising results looking at the lobsters and we've seen promising results with antioxidants, even aspirin, but as I said these things are going to be incremental. You meet a lot of people in the scientific community that are true believers and they're expecting a kind of a radical thing. And it's not as though we never have a radical thing in medicine, but what we have more frequently is incremental advances.

Cancer is a great example of the kind of incremental progress I'm talking about. In 1970, your odds of surviving 5 years after you've were diagnosed with certain kinds of cancer were slim; those chances have increased substantially. But we still react to the idea of getting cancer as though it were 1970 because we don't really process incremental changes. Like with chemotherapy, they just change out one or two drugs every year based on trials that show that the new drug is 2 percent more effective than the previous drug. That's constantly going on, but it really isn't announced. Instead, we get the occasional story in the news about a miracle cure for cancer, and it always turns out not to be as good as they had hoped and everyone begins to get disillusioned about science and the value of medical progress. But when you run the comparisons across decades, you see something much more dramatic.

You give an interesting account of how the aging process evolved in humans. You argue that aging is not the result of an optimizing process, but that instead it's a byproduct of an optimizing process. Can you explain why that difference is so important?

Foddy: I should say, first of all, that this is not original to me; this is very well established in evolutionary biology. We have a number of genetic traits that we developed because they were advantageous from the perspective of natural selection---that is, they helped us to survive and reproduce. People that had the gene for that trait had the ability to reproduce more than people that didn't have it. It's easy to imagine that every gene that we have is selected because it gave a positive advantage in this way, but it turns out there are trade-offs. A number of the processes of aging seem to have arisen because our bodies were not doing enough maintenance, because they were busy doing something else. The misconception that people often have is that any trade-off that we have is going to be directly beneficial, directly advantageous. But that's not right.

The second thing to say is that aging usually happens to an organism after it reaches menopause. Things that happen after menopause are much less interesting in terms of evolution, because they have much less of an effect. If I've already reached the age where I can't reproduce, then aging that takes effect at this point in my life is not going to affect whether or not I reproduce. The game is sort of already over for me. As a result, natural selection doesn't tend to weed out genes that take effect after you've reached the age of menopause. So, there is this idea that over time you can amass genes in your genome that have nothing to do with survival or not surviving, because they only activate after you reach a certain age. So, over time, some of these are going to be good genes and some of them are going to be bad. It's going to be this kind of mix, but it's certainly not going to be the case that they're on balance beneficial. We've got hundreds or thousands of genes that don't start to harm us until we reach old age, and those genes are responsible for a lot of what actually constitutes aging. So, in this sense, we think about aging as being a natural human activity or a human trait---and it is natural, but it's not something that was selected because it was beneficial to us. There is this misconception that everything evolution provides has to be beneficial to individuals and that's not correct. "There is this misconception that everything evolution provides has to be beneficial to individuals and that's not correct."

One defense of aging that your paper takes quite seriously is the argument from evolution, which was first put forth by Frances Fukuyama. Fukuyama claims that we should resist the temptation to tinker with any characteristic that we have been given through the process of natural selection. He argues that evolution can be relied upon to produce good results and that we ought not to mess with the fruit of its processes. What's wrong with this view?

Foddy: Fukuyama has this idea that evolution is very complicated, which is true. We don't always understand why we've evolved to be a certain way. Sometimes it looks like something is useful, but in fact it's performing some kind of role that we don't know much about. Fukuyama is also correct that sometimes we interfere with complicated biological systems without really understanding what the effects will be, and that then we wind up with some unwanted effect. That's all true.

The thing that I disagree with him about is his presumption that if we have a trait that's evolved, that it must be beneficial to us in some way, and that we have some good reason for allowing that trait stick around. Now he's not talking strictly about aging; his book discusses all kinds of intervention on the human organism. But, when it comes to aging, his argument can't even succeed on its own merits, because we know for a fact that aging is not the sort of thing that is produced by natural selection in the kind of positive way that he is talking about. He says it's not always easy to do nature one better, but that's not what we're doing when we're combating aging. We're not trying to do nature one better, because nature doesn't care that we grow old and die. This is neglect, evolutionary neglect. We shouldn't think about it as interfering with the sort of complex ecological balance in the way that he's worried about.

Now that's not to say that our current mode of life extension is ideal. Some of the biggest strains on our resources stem from the fact that populations are getting older as birthrate's go down, especially in the first world. Aging societies are spending more and more on nursing, and so I think that it makes sense to pursue a youth-extending medicine that would diminish the number of years that we have to spend in nursing homes. You could imagine us living more like the lobster, where we still live to be about 80-85, but we're alert and active until we drop dead. In that scenario we wouldn't have this giant burden where the state has to support and pay to nurse people that are unable to look after themselves anymore.

Now, it has to be said that the story of medicine and medical progress in the past 50 years has not been heading that way. If anything, we're extending the number of years that we spend needing nursing. We've gotten good at keeping people alive once they're fairly decrepit. And that sort of guarantees that you have the maximum drain on resources, while also producing the kind of minimum amount of human benefit. You get to be 90 years old and your hip goes out, and we give you a massively expensive hip replacement, but we don't do things to prevent your body from wasting away and becoming corroded when you're 20, 30 or 40.

There's this great Greek myth, the myth of Tithonus, that always comes to mind. Tithonus was a mortal who was in love with Eos, the goddess of the dawn. Eos didn't want Tithonus to grow old and die, so she went to Zeus to ask for eternal life, which was granted. But, she forgot to ask for eternal youth, and so Tithonus just gets older and older and more decrepit, and eventually he can't really move, and then finally he turns into a grasshopper in the end. That's sort of the course that we're on with our current approach to medicine and life extension.

Some ethicists have pointed out that death is one of the major forces for equality in the world, and that welfare disparities will be worsened if some people can afford to postpone old age, or avoid it altogether, while others are unable to. What do you say to them?

Foddy: I think that's right. I mean there are concerns whenever we develop any kind of medicine or any kind of technology---the concern that these things are going to widen welfare gaps. The story of industrialization is that the people who could afford the cars and machines and factories in Western countries were able to produce a lot more and generate a lot more wealth than people in poorer agrarian economies. That's a serious issue. It's probably true that if people in the first world were, through some sort of medical intervention, able to live to be 200 years old and people in Bangladesh were still dying at a relatively young age, that would tend to widen the distance in personal wealth.

And look this has already happened. It's already unfair that I will on average live to be 80 and yet, if I were born before some arbitrary date, or in some other place, I would live much less longer. Those things are unfair and it's worth worrying about them, but I don't think the correct response is to hold off on the science. It's better if everybody can eventually get this medicine, because living a long time is not a positional good, it's an absolute good. It would be great if everybody could live to be 150, because that would benefit every single person. It's not a good that benefits you only if other people are worse off. When you have goods like that you should try to develop them and then you should worry separately about making sure that they get delivered to people in poorer areas, whether it's through government aid or massive production.

Another objection to the elimination of aging is this idea that the aging process makes an elderly person's death less painful for the survivors around her, because it gradually forces people to stop relying on her, and forces her to gradually remove herself from society. You call this the argument from psycho-social history.

Foddy: This is Leon Kass' argument. He thinks aging is just fantastic for this reason because it helps us to let go of somebody. And of course it's true that when people grow old, they become less useful to society, and more socially difficult, which places burdens on people. And in a lot of cases we respond to this by cutting them out of our lives, essentially. People get older, they move into a nursing home, and we see them less and less, and then when they finally die everyone's like, "well it was expected." Advanced age sort of helps us prepare emotionally for letting go of people, but it seems to me that it's not good for the person who gets old.

Now, what would the world be like if people dropped dead in good health when they reach a certain age? It would be very sad, but on the upside the person would've had 20 or 30 years of additional integration into society and we would've been able to spend more time with them. I've got to say that I would've enjoyed my grandmother's presence a lot more if she'd been able to run around and to play and work and be part of society in her extremely advanced age.

Nick Bostrom has said that people have fallen victim to a kind of Stockholm syndrome when it comes to aging. The idea being that because aging has always been an insurmountable obstacle for humanity, that we have dignified it more than it deserves, that we contort ourselves logically and rhetorically to defend it precisely because it is so inescapable. Does that sound right to you?

Foddy: Yes, I think that's right, although Nick draws conclusions that are a bit more extreme than I would tend to draw. I think that we do have a tendency to kind of rationalize things that we don't think we can do anything about. This is a perfectly healthy attitude if you really can't do anything about the aging process---it's better to accept it and kind of talk about it as being a natural part of life, not something to rail against or feel bad about. It's something that everybody goes through. Now if it did so happen that we could discover a medicine that completely prevents that process from taking place, we would have to re-evaluate at that stage and realize that we've done some emotional rationalization here and the conditions for it no longer apply. We no longer need to comfort ourselves with the inevitability of death if it's not actually inevitable.

Having said that, death is, in fact, inevitable. Even if we solve every medical problem, you still have a 1 in 1,000 chance of dying every year by some sort of accident. So, on those odds you could probably expect to live to be about 1,000. I don't think it's ever going to be the case that we will live forever. It's not even going to be 1,000. We're probably talking about living to be 120 or 150 or somewhere around there, but to me the idea that we have to accept living to 80 rather than 120 is bizarre given that it's not so long ago that we lived to 40.

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