According to the book of Psalms, the length of a human life is “threescore years and ten”, which translates to seventy years in modern terms.

There are examples of people in the Old Testament who lived much longer – like Methuselah who reached the ripe old age of 969 – but we don’t know if these figures should be taken literally.

Seventy seems a reasonable age, even in modern times. Because of medical advances, better nutrition and improved living conditions, people, especially in industrialised countries, often live well into their eighties and nineties.

The Japanese currently have the highest life expectancy and the Swazis of southern Africa the lowest.

The five countries with the highest life expectancy at birth (in random order) are Singapore, Monaco, Japan, Macau and San Marino.

The oldest living person is Misao Okawa, a 115-year-old Japanese woman, and the person with the highest verified age was Jeanne Calment of France, who died in 1997 at the age of 122 years and 164 days, according to the Guinness World Records.

On average, women also live about five years longer than men, and more than 80 percent of people who live to be over 100 are women.

A cut-off point

However well we look after ourselves and however conducive our living conditions are to longevity, there seems to be a genetically determined cut-off point for the human lifespan, which is at about 115 to 120 years. Presently no one really knows why, at a certain point, our cells start deteriorating until they don’t function anymore.

Nowadays most scientists tend to agree that ageing is largely the result of damage to the molecules that form our cells. As damage progresses, our cells slowly deteriorate until our health starts to decline. Our bodies start wearing out like an old machine and eventually we die.

This deterioration of our cells may be caused internally by accumulating errors in the DNA copying process, as well as externally by factors like nutrition, sunlight and cigarette smoke.

Telomeres

Another reason why our cells don’t carry on replicating forever may lie with so-called telomeres. A telomere is essentially a section of DNA at the end of a chromosome which protects it from deterioration.

Telomeres have been compared to the aglets of shoelaces that prevent the ends from fraying. As we age, the telomeres get shorter, limiting the number of DNA divisions – which might be responsible for limiting our lifespan. Telomere shortening is undoubtedly involved with ageing, but we don’t know if the shortening of telomeres is a cause of ageing, or just a symptom of the process.

The shortening of telomeres and the subsequent death of cells may however not be inevitable. In the 1980s an enzyme telomerase was discovered. Telomerase protects the tips of telomeres and can be reactivated.

Studies done on mice indicate that replacing this enzyme can restore health and vigour, which suggests that increasing telomerase in humans could be a step in the direction of the fountain of youth. A possible downside, though, is that telomerase could encourage the growth of cancer in the human body.

Finding the secret of everlasting life, or at least a considerably longer life, is probably not as simple as boosting telomerase production, but it has the potential of one day altering the biochemistry of ageing. Until such time, we’ll have to find less dramatic ways of extending our “threescore and ten”.

There is hope

Left to our own devices, there’s a lot we can do. We all know that eating correctly, reducing stress, not smoking and having loving, secure relationships can help us to live longer, healthier lives, but getting the formula just right can be quite tricky.

It might be useful to take a look at some groups of people who are known for their health and longevity. National Geographic writer and explorer, Dan Buettner, who studies the world’s longest-lived peoples, calls these areas where these people live “Blue Zones”.

According to the New York Times they have the following in common:

  • An environment that encourages a healthy diet and plenty of exercise
  • Healthy relationships with other people and good psychological health
  • Looking after gardens
  • Having a spirit of cooperation
  • Easily accessible public health
  • Being valued as seniors by their families and communities