In this case, a drop of fitness ...

In this case, decrease the fitness of the organism does not necessarily match the proportional decrease in viability. Body can sufficiently ensure its viability, and even so at a time can be "selectively unprofitable." If, due to the low fitness individuals, only produced its resources are sufficient only to ensure its own viability, it is unlikely to produce in the future "production unit" (ie, give birth and raise the child) is very low, even at minimum a lack of resources (not only food), if this individual will create at least a minor inconvenience more efficient distributor of identical genes, this individual will "selectively unprofitable." (Contemporary social environment and conditions in which man lives, minimize the likelihood for it to be "selectively unprofitable": everyone has reached a certain age, a pension and not a burden, each born has a higher chance of survival, there is no shortage of food. But the evolutionary development people mostly took place in a different environment). The most "selectively appropriate" body must maximize its value to take into account sufficiently in the long term viability as an amount proportional to its own relative fitness in the long term, ie should take into account the value of Krets / Kdon. And it means - "threshold" response of self-restraint will depend upon the information coming into consciousness. As follows from the foregoing, the reaction of self-restraint - adaptive features which reduce individual fitness (viability) individuals can form and will be formed in the course of evolution, as signs that increase the inclusive fitness of individuals (as signs of enhancing the effectiveness of the spread of identical genes). Such reactions are caused by irreversible decrease in the relative fitness (relative decrease in the coefficient K) to a critical level. And that means - such reactions will occur based on the information of the real or false, coming into consciousness. As a possible example of the reaction of self-restraint, formed in the process of evolution can cause such symptoms common to many species of animals, like age, a sharp decrease in the capacity for reproduction, with relatively less significant reduction in other body functions. The same sign, perhaps, to some extent, is the age-ending life of the organism - the death of "old age". Age cessation of vital activity, if we consider the body as a biosystem, with no mechanism (adaptive traits) self-restraint, should occur as a consequence of loss of efficiency of individual life-supporting structures - functions, with a gradual decrease in their capacity to zero. Often this is not observed. Age cessation of vital activity often occurs at a fairly high level of efficiency the major life-supporting structures, with their level of efficiency, far enough away from zero.