King David's advisers urged him to clasp a young virgin to his bosom. Pythagoras advocated a diet of acorns, fruit, and grains, while Sir Francis Bacon favored anointing the skin with ointments and pomades. Nowadays scientists turn to fruit flies for clues about how to prolong life. Michael Rose, an evolutionary biologist the University of California at Irvine, has recently reported some eyebrow-raising success. In his lab he has doubled the fruit-fly life span and believes the lessons he's learned will enable humans to do the same. He discussed his research with Discover associate editor Josie Glausiusz.
How did you coax these fruit-flies to live so long?
By tricking natural selection. I wait till they're older before letting them reproduce. The ones who do are those that have already proven they can live that long and have the physiological wherewithal to reproduce. Multiple generations of this procedure makes them live better than twice as long. Are they immortal?
The flies in my lab potentially can live forever. But of course they don't, because they have a high likelihood of dying by accident; getting stuck in the medium and falling over face-first and drowning— the regular stuff. What have fruit-flies taught you about human aging?
The most important thing is that it tells us that aging is in no sense any basic feature of cell biochemistry. There are lots of organisms that have the same kinds of cells that we have but don't have any aging at all— organisms like hydra, sea anemones, some types of flatworm, quite a few grasses and shrub species. Aging just isn't some God-given inevitable thing. It is something you can change and control. Why do humans age but sea anemones not?
To age means that you are less and less able to survive and reproduce with time. [Hydra] reproduce by splitting, so they survive indefinitely. We reproduce with tiny little gametes— the cells that carry out our Darwinian mission. The rest of us is dispensable, a disposable shell. What natural selection is saying to us as we get older [and past reproductive age] is, "Frankly, I don't give a damn about you any more," like Clark Gable in Gone With the Wind. So we get progressively more and more decrepit. How might humans live longer than we do now?
Say that we find out that a particular enzyme, like superoxide dismutase, [a scavenger of destructive free radicals] needs to be very active in order for you to live longer. Well, once we work out all of the details of dosage, then it might be that once every month you go to your physician and he injects you with the enzyme, which circulates around in your body to help slow your aging process or reverse it. And so on with all of the other possible substances that one might use. How likely is such a scenario?
I'm not saying any of this is magic. I'm just saying it's something you could do. And I really would hate for that to be represented as my immediate medical advice to anyone. What we know of aging is that it is very complex, and you want to approach any intervention with great care. Because I am not an advocate of the quick fix. Do you want to live to be 200 years old?
I don't wake up in the morning and think about how I'm going to live longer. I should explain that unlike most people from this field, I did not start working in this field for my personal longevity. I only started working in it because my advisor told me to. For me it's an interesting scientific and technical puzzle, and not a personal quest. Is there any advantage to living any longer than we do now?
There are two answers to that question. Mozart and Jimi Hendrix. Mozart died at 35. Jimi Hendrix died at 27. If Mozart had lived another twenty years, I would have a still larger music collection, and the same thing with Jimi Hendrix. On the other hand, there's probably not much point in having mathematicians live past the age of 40, or scientists live past the age of 50. Both mathematicians and scientists do very little that's important past those ages. There are other occupations, like novelists and historians, where you do better the older you get. So for those occupations, a greater life span is all to the good.
Couldn't life get a bit boring if you lived indefinitely? What if we lose all our faculties?
I'm the wrong person to ask that question, because my point of view is that my life has never been boring. [As far as faculties go], my fruit-flies that have postponed aging have enhanced performance. What they can do when normal flies are long-dead is absolutely amazing. These flies are fornicating like crazy. When normal aging flies have just completely given up, they're going nuts. They can fly around and walk around much better. They're just totally dynamic and vigorous, when normal flies are barely moving around.
How do people respond to your ideas about extending human life?
There are all kinds of people who are opposed to us doing anything. The Federal Government has this need for us to die on our due date, so you don't bankrupt Social Security or Medicare. And I have on a number of occasions heard people give very moving addresses as to why we should die as soon as possible. I think the phrase that most stuck in my mind was "So that we can know God's love sooner." And let me just say for the record, I am all for those people dying. They can go ahead. I just know other people who don't want to die, and least of all by the horrible and unattractive process of aging, and I don't see any reason why they shouldn't be allowed to go on living.
Is there any limit to the human life span?
No. Not at all. In fact, I have been quoted as saying that the limit of the human life span is the limit of human technology. What is your greatest fear?
In common with many scientists--especially evolutionary biologists— my greatest fear is of a world dominated by superstition, in which people are told what to believe, with the threat of torture and execution if they don't believe what they are supposed to believe. In other words, the Middle Ages.