Most people including many scientists and physicians think of aging as inevitable, inexorable, and inescapable, but recent discoveries have shown that it is not any of these things and lead to the conclusion that ways will be found to very significantly delay the effects of aging.
Much more recent, more extensive, and more comprehensive treatment of this subject can be seen in the free online book The Evolution of Aging available at http://www.azinet.com/aging/
Some time ago it was found that semi-starvation extended the lives of rats. Initially, it was thought that this increase in longevity might be caused by a general metabolic reduction which generally slowed the processes of life including aging, a not very useful finding.
More recently, careful Caloric Restriction (CR) experiments have been performed in which animals are fed significantly less food than they would naturally eat if plenty of food was available. Their diet had all the essential vitamins and nutrients but was restricted in terms of calories.
The CR animals were found to be more active, less susceptible to disease, and lived up to fifty percent longer than animals on an unrestricted diet. They not only lived longer, they stayed younger longer. This effect has been observed in all the mammals for which data is available and is presumed to also be present in humans (although volunteers for long term experiments have been hard to find). Apparently diet has a much more direct and significant effect on aging and life span than previously thought. Dietary restriction appears to delay the activation of a biological aging mechanism.
Research is under way in an effort to find ways of simulating the effect of CR on the aging mechanism so that people will be able to have the beneficial effects of diet restriction without actually restricting their diet so much.
Another major discovery is that a few species of fish (sturgeon, yellow-eye rockfish) and turtles apparently do not age. These animals do not show any loss of strength, agility, or reproductive activity with age or any increase in mortality or disease with age. People are catching 140 year old rockfish. Researchers are studying these animals in an effort to identify the genes, hormones, and other aging mechanism elements (missing or different in them) associated with aging in normal animals.
Aging genes have been identified in animals such as mice and worms and are expected to be found in most animals and humans. When the gene is disabled using genetic engineering, the animal lives longer by at least 30 percent. These genes have no identified function other than causing aging. Researchers hope to be able to find ways of inactivating or contravening the effects of human aging genes.
There are rare human diseases (Hutchinson-Guilford progeria and Werner's syndrome) which apparently cause a premature activation of the aging mechanism. Victims display characteristics and diseases associated with age such as baldness, gray hair, skin conditions, weakness, heart disease, joint disease, and cataracts at ages as young as ten. Genetic comparisons between victims and normal people should help identify the genes and other elements of the aging mechanism.
Attitudes regarding aging among the public, legislators, medical people, and some biologists, such as the idea that aging is fundamentally inescapable are inhibiting anti-aging research. (The U.S. national anti-aging research budget is less than the national bubble gum budget.)
The attitude problem is exacerbated by major differences between groups of scientists regarding various incompatible theories as to the causes of aging. The foundations of these theories date back to at least 1859 and Darwin's theory of evolution. Proving or disproving any particular theory (to the satisfaction of the opposing group) approaches impossible (It is hard to do experiments involving trillions of animals and billions of years!) so the theories live on for (in some cases) over one hundred years with no resolution in sight. Some of the theories (and their adherents) support the idea that aging is "an inescapable biological reality" and that basic anti-aging research is therefore essentially futile and foolish, a "search for the fountain of youth", despite the evidence outlined above. Other theories are much more optimistic. From a practical standpoint, the largest difference in opinion appears to be whether aging is or is not an evolved characteristic or a feature of an animal in exactly the same way that feet, fur, and fangs are evolved features (or adaptations). Theories (there are several) that consider aging an evolved feature and part of an organism's design (such as the evolvability theory) tend to be more optimistic regarding the possibility for major treatment of the fundamental cause(s) of aging.
Adaptive aging is scientifically unpopular largely because it is incompatible with the details of Darwin's theory of evolution. However there are at least three proposed minor adjustments to Darwin's theory, some of which support aging as an evolved characteristic. Adaptive aging is only one of several Darwin's theory discrepancies.
An in-depth discussion of aging theories and associated evolution theory issues can be found in the complete book. See this list of on-line resources for links to more about theories of aging.
T. C. Goldsmith July, 2002 firstname.lastname@example.org rev 9/03
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