The search for the secret of eternal youth is as old as history. But while there has never been any shortage of purported remedies, none has so far left a lasting impression. For a hunt lasting more than 5,000 years, ground-up monkey testicles, a diet of fresh air and a Jane Fonda fitness video represent a relatively poor return.
Things, however, may at last be looking up. These days, biologists are pinning their hopes on the most unlikely of heroes: the fruit fly, Drosophila melanogaster. Lessons learned from fruit fly Methuselahs could one day provide a stepping stone towards our own immortality.
This is not the first time that the fruit fly has illuminated a murky biological puzzle. Time and again over the last hundred years, the fly has been at the cutting edge of some of the biggest biological discoveries. Genetics, embryology, evolution and animal behaviour have all been built on the foundations of fruit fly research.
Today, the fly crops up in all sorts of unlikely places: in the search for cancer cures; as an early-warning system for global warming and climate change; in the study of neuro-degenerative disorders like Alzheimer's and Huntington's diseases; and in understanding the genetics of alcohol and drug sleeping disorders and jet lag.
It might seem strange that an insect no bigger than a grape pip can teach us anything, let alone anything about ourselves. But despite being separated by more than 500 million years of evolution, humans and flies still share many genes in common.
Take the genes responsible for orchestrating and directing a fruit fly's egg to develop into an adult. Since their original discovery, similar developmental genes have turned up in sea slugs, frogs, mice and humans. Far from being unique, fruit fly biology often proves to be a reliable guide to life in general.
But why is it that the fruit fly has become such a prominent scientific star? Why not a chimpanzee, a peacock or some other glamorous creature? In large part, it boils down to simple economic realities. A half-pint milk bottle containing a rotting piece of fruit makes a luxury hotel for over 200 fruit fly residents.
Put two amorous flies in a room together and within a few months you will have more descendants than there are people on earth. In short, fruit flies do pretty much what other animals do - eat, sleep, have sex, grow old and die - only cheaper and faster.
Of course, flies and humans have their differences. But they are far from stereotypical simpletons. The fruit fly can be trained by punishment and reward to learn and memorise information, to distinguish different smells, for example. What is more, the fruit fly's memory seems to work in a remarkably similar way to our own.
The fruit fly has proven itself to be an ideal role model for biology. So perhaps we should not be too surprised if it throws some new light on the perennial problem of ageing. Through genetic engineering and selective breeding, laboratory fruit flies are living longer and growing old more gracefully than ever before.
Flies have highlighted the importance of anti-oxidants, chemicals that repair molecular damage to the body's cells. Evidence suggests that slower rates of ageing and a longer life come to those who are good at resisting or repairing such damage. For us humans, eternal youth may have to wait a while. In the meantime, we might do well to keep a close eye on the fly.
Martin Brookes is the author of Fly: An Experimental Life published this month by Weidenfeld & Nicolson £21.50