NEW YORK, Jul 14 (Reuters) -- Examples from nature suggest that there may be no limit on human longevity, says one biologist.
The existence of millennia-old trees and 140-year-old fish "suggest that no firm limit (to lifespan) is built into the human genome," concludes biologist and gerontologist Dr. Caleb Finch of the University of Southern California, Los Angeles.
In his report in the July issue of the Journal of Gerontology, Finch calls for the creation of a longevity-research "tissue bank," built to house the DNA of some of the world's oldest plants and animals. These samples could be used to research anti-aging mechanisms.
The record for a documented human lifespan is 122.4 years, achieved by the Frenchwoman Jean Calment, who died in 1997. However, this advanced age pales in comparison to that of the world's oldest living organism, a 4,862-year-old bristlecone pine found in the high Nevada mountains of the western United States. Finch adds that certain animals, including the rockfish of the Northwest Pacific, or the orange roughy, found in southern oceans, routinely achieve lifespans of 140 years or more.
He points out that as humans reach extreme old age, the physiological vitality of their earlier years becomes a distant memory and they exist "in a very fragile state." This is because human life, like that of most mammals, follows a pattern of "gradual senescence" -- the "switching off" of reproductive ability in mid-life, followed by a slow but steady decline in physical and mental function.
However, the bristlecone pine, the rockfish, and other long-lived species do not follow this pattern. Finch says researchers have noted "an absence of age changes in (the) sexual reproduction of trees aged 700-4,713, as judged in the laboratory by pollen germination, by seed weight, and by seedling growth rates." In fact, if they are not destroyed by fires, insect infestation or other hazards, most bristlecone pines retain their "youthful" vigor well into their fifth millennium. Similarly, Finch says that the examination of very old rockfish revealed that females had "abundant, newly formed eggs and... appeared in fine health."
The fact that these animals seem to escape aging suggests that the process itself may not be inevitable. Finch says this "plasticity" in lifespan points to hormonal and environmental factors, not genetic programming, as the prime determinants of longevity. If that is the case, "efforts to modify human aging via drugs, diet, and lifestyle interventions are entirely consistent" with those lifespan modifications seen in other species, he says.
Finch cautions that many of these rare, long-lived species are under serious threat of extinction from mankind. He therefore advocates the creation of a "tissue bank... to provide specimens of long-lived organisms for the study of possible anti-aging mechanisms that permit achievement of great ages." Finch believes these species "are among our old Earth's greatest treasures and should be included in endangered species efforts."
SOURCE: The Journal of Gerontology: Biological Sciences 1998;53A:1740-1748.
