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Robert R. Kohn, PhD, MD
JAMA. 1983;249(17):2328-2329. doi:10.1001/jama.1983.03330410026016.
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In Reply.—  Certainly no present-day gerontologists believe with regard to parts "that all are ready to fail when the first one fails." Many cells and intracellular components are functioning perfectly well right up to the end. Evidence is accumulating that stem cells do not age.1 The concept that there is a well-defined limit to the human life span and that it is not "far beyond a century" is not based on the cause-specific age at death but on the experiment represented by every human being who was ever born. The experiment always turns out the same—no one lives longer than "100 or so." Regarding mechanism of aging deaths, Dr Weiss is wrong in stating there are no undisputed biologic data. There is an enormous amount of information available on progressive, harmful aging processes. Such data were mentioned in my article and are frequently reviewed.2,3 Among the most important


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