ABSTRACT
A useful approach to the introduction of any book about the biology of aging (after first clarifying the essential terminology) is to consider three traditional questions that have always driven biogerontological research. In keeping with that philosophy, we first shall give a brief summary of what can be referred to as senescent phenotypes (What is aging?). We will conclude that there is a remarkable range of senescent phenotypes that impact physiological functions at all levels of analysis and in all body systems. Next, we will consider what is surely the most fundamental of all gerontological questions (Why do we age?). The evolutionary biological theory of why aging occurs remains by far the most satisfying explanation, although there have been certain challenges to that idea. Finally, we will very briefly introduce the third-and by far the most difficult-question, one to which the modern tools of molecular biology and genetics have only recently begun to be successfully applied (How do we age?).
