Over the many ages of man, life expectancy has gone up and down depending on several factors. Neanderthals, for example, had an average life expectancy of 20 years. The short life span was likely caused by a way of life that was much more dangerous than we now know.

Mankind's never-ending race to find the fountain of youth may never be over, but the more we learn about the human body, the healthier we are for it. Even in today's world of fast food and desk jobs, people are finding ways to eat healthier and live longer. Recent life expectancy studies show an average of 78 years in the United States.

According to University of Pennsylvania demographer Samuel Preston, "We (in the United States) are two to three years behind most Western countries at this point. We may be gaining, or not gaining, depending on the rate at which their life expectancy is increasing. The male versus female difference in life expectancy has declined over the past 15 years. It was previously eight years; it's now five. Another positive trend is that the life expectancy of blacks has been increasing relative to that of whites."

Average life expectancy in Japan is 82 years. Some residents of the Japanese island of Okinawa rank among the oldest people on the planet. In 2002, nearly 35 people per 100,000 there were over the age of 100.

Andorra is a small nation in the Pyrenees Mountains between France and Spain. Its residents hold the top spot for longevity. Andorrans can look forward to a life expectancy of 83.5 years on average.

Potential Secrets to Longevity

Each country with high life expectancies claims a certain amount of responsibility for the longevity of its citizens. In the Balearic Islands, for example, one 114-year-old man who recently died was the subject of study by doctors there for a few years before his death. He cycled to work in his family orchard until he was 102 and believed leading a physically active life and eating his native diet added to his life span.

Different cultures vary on what they believe to be the secret of longevity. The Japanese say vegetables are the key, Greeks say olive oil, and the French say red wine. Many Americans swear by exercise, while Cubans say cigars are the key to longevity.

The Real Secret to Longevity May Never Be Known

Because human beings are so different in so many ways, geneticists have not uncovered the true secret to longevity. Geneticists, doctors and other medical and scientific professionals may never agree on one theory over another. The background and genetic makeup of every individual are so incredibly diverse that one true secret may never be known. There are, however, a few things all the professionals can agree on. Proper diet, moderate exercise, limited stress and no smoking all aid in living longer and healthier lives. So while we may not yet know the secret to longevity, we are certainly familiar with the basic building blocks for it.