Ontogenetic model of ageing and disease formation and mechanisms of natural selection.

It is known that increased mortality due to environmental hazards results, in the course of natural selection, in the shortening of maximum life span and acceleration of sexual maturation in a population subjected to an intensified pressure from external environment. As a consequence, the prereproductive period/maximum life span ratio appears to be approximately the same in each species. Mechanisms responsible for this are not clear yet. Since maximum life span is limited by both ageing and formation of certain diseases (in humans, the so-called main noninfectious diseases), the paper discusses four possible models of development of ageing and age-linked disease--ecological, genetic, degenerative (metabolic) and ontogenetic. It was found that it is the ontogenetic model only that can adequately account for the development of moderate shifts in the duration of both sexual maturation and maximum life span. It also provides the rationale for the pleotropic activity of genes during the development of the organism, its ageing and formation of age-connected diseases.