On the Art of Prolonging Life was penned by a Dr Huseland (“one of the soundest minds in Germany”) in 1797, concluding eight years of study on the topic. He identified among the many factors associated with long life: a moderate diet that was rich in vegetables and short on meat and sweetened pastries; an active lifestyle; good care of your teeth; weekly bathing in lukewarm water with soap; good sleep; clean air; and being born to parents who themselves lived long lives. Toward the end of his essay, translated for the American Review, the doctor wistfully speculated that “human life may be prolonged to double the extent of what is supposed to be its present limits, without losing activity and usefulness.”

By Huseland’s estimates, half of all children born would die before their tenth birthday, an alarmingly high mortality rate. However, if the child could run the gauntlet of youth fraught with smallpox, measles, rubella, and other childhood diseases, they stood a fair chance of making it all the way to their mid-thirties. In ideal circumstances, Huseland thought it possible that a lifetime could stretch for two hundred years.

Is there more to these claims than the fanciful imagination of an 18th century doctor? James Vaupel doesn’t think it’s out of the question. “Life expectancy is increasing two-and-a-half years every decade,” he says. “That’s twenty five years every century.” As director of the Laboratory of Survival and Longevity at the Max Planck Institute for Demographic Research in Rostock, Germany, Vaupel studies longevity and survival in human and animal populations. He tells me that the pattern of improvements to mortality has shifted greatly in the past 100 years. Before 1950, most of the gains in life expectancy were made by combating the high infant mortality that Huseland noted. Since then, however, it’s been the over-60s and most recently the over-80s who’ve seen the greatest decreases in mortality.

In other words, we are not just surviving childhood in greater numbers, we’re living longer – a lot longer.

Age complex

Worldwide, the number of centenarians – people over the age of 100 – is predicted to increase 10-fold between 2010 and 2050. As Huseland testified, a strong component in whether you’ll live to see this milestone lies in the age of your parents; that is, there is a genetic component to long life. But the rise in centenarians can’t be explained by genetics alone, which clearly haven’t changed much in the last couple of centuries. Rather, it’s a host of improvements to our lives that cumulatively improve our chances of living longer and stronger, many of which echo the factors identified by Huseland. The reasons include better healthcare, improving medical treatments, public health measures like cleaner water and air, better education, and improved standards of living such as houses that are warm and dry. “Mostly it’s down to having more medicine and money,” says Vaupel.