Bio-genetic theories of ageing

During the twentieth century, understanding of the significance and function of nucleic acids, DNA and RNA, and core mechanisms of the cell as well as discovery of antibiotics and, consequently, increasing progress of pharmacology, have determined, especially in industrialized countries, a radical change in the conditions and duration of life. Currently, in Italy, the average life expectancy is 80.1 years for men and 84.7 years for women. Although these data (unthinkable 100 years ago) represent an extraordinary outcome, nevertheless, they also pose new social, health and economic challenges. In fact, since the improvement in life expectancy is necessarily associated with a significant increase in the incidence and prevalence of diseases typical of the elderly, the study of biological and physiological features of ageing may hopefully provide useful tools to give relief to the pathological and, eventually, painful aspects of old age. In this context, our review addresses the main theories of ageing: genetic, unbalanced homeostasis and cell damage theories. However, it should be stressed that these theories (in spite of their monistic attitude) do not exclude each other and that ageing and longevity are to be considered multifactorial and very likely modulated by a combination of endogenous and exogenous factors, even if with some elements bearing more importance than others. Moreover, although organisms resemble in many ways, living systems are very heterogeneous and the maximum lifespan could even be determined by completely different factors in diverse species.