The Future of Aging Interventions: The Human Life Span Is Not That Limited: The Effect of Multiple Longevity Phenotypes

Abstract

There is an ongoing debate as to whether or not human longevity is approaching its limits. The debate and its outcome are important since they might affect public policy. We review the evidence presented by both schools. We add our empirical observation that there exist multiple longevity phenotypes, each of which arises from the alteration of fundamental aging processes. The current debate only considers two of the three known mammalian longevity phenotypes. The overlooked phenotype is the delayed onset of senescence phenotype, which can be induced by various interventions, including pharmaceuticals. The existence of multiple phenotypes means that an overview of potential life expectancy outcomes for a species should be based on the analysis of all longevity phenotypes likely to occur in that species.

Consequences of increased longevity for wealth, fertility, and population growth

“…Immortals have m ≥ 6. The number of mortals roughly decreases as 2 −t while their individual wealth oscillates in the interval [1,6). In fact, numerical simulations show that the majority of this population oscillates in a narrow interval of wealth around (2) it follows that immortals can procreate only if economic growth is such that γ > 3/2.…”

“…The picture that is emerging is quite unexpected [3]. We are getting farther from the concept of "natural death" as an immutable and inevitable end of life [4][5][6].…”

Human Reproductive Costs and the Predicted Response to Dietary Restriction

“…58 In this baseline model, somatic maintenance reaches a peak level under DR conditions, presumably as an result of the effects of low caloric intake on one or more upstream signaling pathways that then act on the sirtuin genes and the downstream FOXO-de- The adult span is further envisaged as comprising the health span and the senescent span. 8 These supraorganismal resource transfers are to be viewed as being superimposed on top of the previously described cell, tissue, and organ level interactions (e.g., see Figure 9.6 of Wilson et al 71 ). During the developmental span, there are significant inputs of energy and information (see text) that significantly lowers the mortality rate.…”

“…It seems to explain some of our own observations on the demography of normal-and long-lived Drosophila. 8 The theory's strengths make one hope that it can be successfully modified to include the missing variables, and so the metabolic stability theory deserves serious consideration (see Sanz et al 55 ).…”

“…Thus it can logically be argued that a decreased susceptibility to disease need not necessarily translate into a significant increase in both mean and maximum life spans. 7 This does not seem to be the case in Drosophila and other animal models, 8 but it is premature to assume that humans will react in the same manner as do these behaviorally simpler model organisms. 9 This debate will eventually be settled by empirical data.…”