Reply #94: You raise some very interesting thoughts.

[Jackpine Radical]

http://www.albionmonitor.com/5-27-96/agingmax.html

Could People Live to 120?

by Eric Mankin

(AR) LOS ANGELES -- Can we cross out the biblical three score and ten as the span of a human life and write in a round six score?
A life span of about 120 years is the maximum that humans can attain under current medical and environmental conditions. But 120 might become the average life expectancy if medical advances could duplicate the mechanisms at work in the only life-extension technique now known to be effective in lab rodents -- extremely low-calorie diets -- say two University of Southern California scientists.

Environment and "alpha factor" determines how long we live

In a new analysis published in the May issue of the Journal of Gerontology, USC scientists Caleb E. Finch, Ph.D., and Malcolm C. Pike, Ph.D., use updated comparative data from animals and a well-known mathematical relation to recalculate the potential human life span. Their analysis also suggests an explanation for certain discrepancies that scientists have previously found in mortality data.
The Finch-Pike study uses the Gompertz model -- named after Benjamin Gompertz, the British actuary who first described it in 1825 -- to predict maximum life expectancies for various species.

The Gompertz rule predicts that the risk of dying accelerates at a constant rate over time for all organisms, be they fruit flies or humans. After human beings reach puberty, for example, their chances of dying increase by approximately 9 percent each year -- thus doubling approximately every eight years. This steady acceleration of death risk, called the alpha factor, is particularly striking in that it seems to hold for humans (and certain other animals) living under all kinds of environmental conditions, whether harsh or benign.

A 1990 Science paper by Drs. Finch and Pike and Matthew Witten (of the University of Texas at Austin) cited the example of Australian soldiers in Japanese prisoner-of-war camps during World War II. All age groups suffered higher death rates than their counterparts back home in Australia. Indeed, both 24-year-old and 48-year-old prisoners were approximately 30 times more likely to die in a given year than their same-age counterparts in Australia. But the acceleration of death rates between the two age groups remained constant. In other words, the 24-year-olds died in the same ratio to 48-year-olds in jungle death camps as in Australian cities and towns.

"The Gompertz model," Finch explains, "allows scientists to express life expectancy as a product of two distinct factors. "One is environment, either stressful (as in the prison camps) or benign. "The other, designated by the alpha factor, is a measure of a built-in species clock, something that seems to be part of our design as animals, a burden of aging that keeps accumulating, like interest compounding on a debt. It includes spontaneous diseases of all kinds, which are largely responsible for the alpha factor."