Jewish World Review Feb. 26, 2001 / 3 Adar, 5761
http://www.jewishworldreview.com -- SAN FRANCISCO | Can humans live happily ever older?
With our genes deciphered and the prospect for a cure for almost every disease seemingly in the offing, scientists meeting here recently pondered just how long humans might expect their lives to stretch in another century or so, and what that might mean for our society.
Life expectancy at birth is greater now than at any time in human history, expanding most markedly -- into the late 70s -- in much of the industrialized world, but also lengthening into the 60s in developing countries as well.
The U.S. experienced a 27-year increase in life expectancy over the past century -- equivalent to all the increase in longevity accrued in humans over the previous 1,900 years, according to Leonard Hayflick, a professor of anatomy and aging expert at the University of California, one of several speakers at a longevity symposium at the American Association for the Advancement of Science annual meeting.
"There is no evidence that human life span is approaching a limit,'' said Dr. Kaare Christensen, an epidemiologist at the University of Southern Denmark. "Death rates for octogenarian females have been reduced by 50 percent, the population of centenarians has doubled every 10 years and the record for maximum lifespan has been repeatedly broken.''
If progress in longevity can continue at the same pace, he calculates that half the women born in Japan and France born in 1999 will still be alive at the dawn of the 22nd century, with Americans a bit behind.
But Hayflick, a pioneer in establishing that normal human cells have a finite ability to replicate, figures that the upper limit for any person to live is about what it's been for the past 100,000 years - around 120 years.
If heart disease, stroke and cancer are beaten, he said, people might expect to live another 15 years, on average. But he notes that "even if all or most causes of death now written on death certificates of the elderly are resolved, it won't provide immortality for all of us. Super-longevity is simply not possible.''
The truth is, despite Methuselah and other long-lived personalities in the Torah , old people are pretty much a new thing. Human fossils indicate few, if any, of our ancestors made it past 50. Biologically, we're programmed to live long enough to reproduce and nurture children to sexual maturity, and any extra capacity our bodies have is just insurance for the species.
Of course, humans didn't just all keel over before they reached 50, but older bodies easily succumbed to injury and disease in prehistoric times. Civilization made it a little easier to grow old, but living longer really only took off when personal and public hygiene improved and vaccines and antibiotics controlled many once-deadly infections.
Now, chronic and degenerative diseases and cancers are the main threats to aging bodies, but seniors are also coming into old age healthier and with more and more medicines aimed at preserving that health.
Nonetheless, the population is graying. And "repeating the dramatic gains in life expectancy achieved for human populations during the 20th century can only occur if biomedical researchers can discover how to modify the aging process and make such a discovery widely available to the entire population,'' said S. Jay Olshansky, a professor of public health and aging researcher at the University of Illinois and the University of Chicago.
He estimates that a life expectancy of 85 is the best that Americans can hope for in the next century, and that a 50-50 chance of seeing 100 at won't become common for several more centuries.
Hayflick says he sees no way that human aging can be slowed, let alone stopped. Even if an age-arresting pill is formulating, he questions whether society could handle individuals making a choice of whether and when to stop aging. Money is better spent on research aimed at improving the health and quality of life for the years we've already got, he contends.
Yet many biomedical researchers are making serious efforts to understand how and why organs and cells wear out, and they are considering a number of arrangements to grow replacement parts , or even to somehow reprogram genes to encourage continued cell growth.
"Life span, like all history traits, is plastic,'' said Dr. George Martin, a pathologist and geneticist at the University of Washington School of Medicine in Seattle. "We know that in the lab you can take fruit flies and select for fruit flies that can live 50 percent longer than usual. So there is an opportunity for substantial increments in human life span.''
But tracking down all the genes that seem to go wrong at different times in life won't be easy. Martin estimates that as much as 7 percent of each person's genes control some facet of how we age. "The picture that emerges is that there are many 'Achilles heels' within each of us,'' he said.
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