Hayflick does not suggest a hard limit to human lifespan, as we have the ability to alter our environment and mitigate the effects of disease, reducing the probability that exposure to disease will be fatal. But Hayflick does state that “human life expectancy has NOT increased as a result of interventions in: 1. Longevity determining processes. 2. Aging processes. 3. The use of cover-ups (hair dye, cosmetic surgery, etc.).” He further notes that “Human life expectancy has only been increased by presenting, resolving or delaying the manifestations of disease ….”
This is an important observation. If, in fact, study of the aging process and the genetic determinants have not and cannot be expected to allow us to extend potential life expectancy, then it will be difficult to generate substantial interest in the study of this process in our results-oriented society. Thus, while study of the aging process and the genetic determinants of our cellular mechanisms for repairing deterioration are of interest, they may be expected to continue to take a secondary role in research behind efforts to develop specific disease interventions and healthy lifestyle strategies.
I find it hard to be this pessimistic about the prospects for extension of potential life expectancy. While it seems implausible to expect extension of life indefinitely, given the seemingly inevitable cumulative deterioration that Hayflick describes as aging, it is equally difficult to set a specific age beyond which we would believe life is not possible. This discussion leads easily to the second paper presented in this session.
Mortality Compression versus Changing Symmetry
In their paper, Robine, Cheung, Horiuchi and Thatcher question whether there is a limit on the extent to which mortality can be compressed. Mortality compression here refers to the shrinking of the distribution of deaths by age among adults. The ultimate compression would be for all individuals who reach adulthood to die at the same age.