“In fewer than one hundred years, human beings made greater gains in life expectancy than in the preceding fifty centuries.”

This sentence opens the book “The Longevity Revolution” published last month by Robert Butler, M.D. It calls attention to a reality that has already profoundly changed the lives of people who live in the United States and other industrialized countries.

And it will bring about further changes of great significance.

From the year 1900 until now, we have gained some 30 years of life. When my parents were born, in 1898 and 1899, average life expectancy was only 47 years. Now it has reached almost 80.

Of course, statistics like this do not mean that everybody lives long. Regrettably, some of us die before reaching 20. I still mourn the loss of a nephew at that age.

But most Americans now, given the breaks, can anticipate living long lives. In fact, we can expect to last as many as six decades more than those who lived back in the Stone Age.

The nation’s leading geriatrician, Dr. Butler deserves be a household name. Among his many accomplishments, he established the first American hospital department of geriatrics, at the Mount Sinai Medical Center in New York City.

In 1975 he published a book that won the Pulitzer Prize. Entitled “Why Survive,” it called attention to the plight of old people in this country.

In that same year, he became the founding director of the National Institute on Aging, the federal agency that sponsors research on issues of aging. In 1990 he opened the International Longevity Center in order to focus attention on world-wide aging and to work for the well-being of people who have reached later life.

He uses “revolution” in the title of his newest book to indicate what a powerful influence our gains in life expectancy have been and will continue to be. As the increased number of older people takes hold, almost every area of national and international life will be affected.

To me, the increase in life expectancy inspires awe and deserves to be hailed as one of the greatest achievements in history. Making it happen took marvelous human ingenuity and the pooling of many talents.

Most Americans now have much longer time in which to lay hold of the experiences that life offers. Having seven, eight, or more decades at our disposal allows us to lead more varied and productive lives.

However, the New York Times last week published accounts of new and disturbing research. Studies show that some Americans, rather than gaining in life expectancy, are actually losing ground.

Researchers at Harvard have identified 180 U.S. counties where life spans for women have declined. The greater number of these women live in the southern parts of the country and many suffer from the effects of smoking, obesity, and hypertension.

This further sign of the divide between haves and have-nots comes as a disturbing reality and shades the rosy picture presented above.

And, for some of us who do live long, the extra time can bring us more grief. We may find ourselves confronted with diseases, disappointments, and unexpected debacles of one sort or another.

However, much as I regret what some of my age peers have to undergo, I feel thankful because so many of them, and I too, have had extra time. I feel glad to have seen things happen that a short life would have made us miss.

For me, seeing my daughter advance into adulthood rates as the number one benefit. As a relatively late-life father, I sometimes feared not living long enough to see this happen.

I also feel glad for a long marriage, rather than one cut short by my not surviving middle age.

Seeing my extended family stretch further also counts as a notable plus. Getting to meet the children of the younger generations comes as a pleasure worth waiting for. A recent dinner shared with my wife’s nephew’s charming children, for instance, reinforces this feeling.

Having had scope for several careers, rather than just one, also pleases me greatly. I have been given world enough and time to know what it is like to live in a variety of roles. My time in religious ministry proved gratifying; so has secular work later on as a consultant and writer.

This phenomenon of changing jobs has become routine now among Americans. On average, we are said to hold at least nine different jobs in our lifetime, and several careers as well. These “encore” experiences bring satisfaction to many people as we discover new interests and skills.

I also welcome the opportunity to see new inventions. The stupendous changes brought about by the computer are a phenomenon I would not have wanted to miss.

The changes in my lifetime have been extraordinary; and to be able to take the long view is an unexpected gift.

Richard Griffin