Michael A. Singer 
Is Aging a Disease? Untangling the Relationship [PDF ebook] 

Each species has its own characteristic aging trajectory coded by a species-specific developmental program. This developmental program is triggered at the time of fertilization, hence aging begins at conception. Within a species there are considerable variations in the aging phenotype between individuals due to the plasticity of the developmental process and its inherent stochasticity. The evolution of a species is due to genetic changes in its underlying developmental program and when enough genetic changes have accumulated a new species emerges with its own characteristic aging phenotype. Therefore, speciation and aging are linked processes. Over the evolutionary course of the human lineage, culture has been an important driver of evolutionary change. Culture is not restricted to the human lineage but only humans have evolved cumulative culture; the transmission of modified cultural practices across generations. Early cultural innovations such as toolmaking, agriculture and dairy farming had a utilitarian function. However, over the past 100 to 150 years, there has been a significant change in the pace and nature of cultural innovations. Although many cultural innovations still have a utilitarian function, a new category of cultural innovations has emerged that have "entertainment" functions in the domains of social communication and information transfer. In addition, cultural practices by the tobacco, food and technological industries have been used to modify population behaviors, physiology and beliefs. Over the past 50 to 75 years, there has emerged so called chronic non-infectious diseases, which occurrence parallels the development of these new cultural innovations and practices. In addition, culture has now become the primary driver of human evolution. In answer to the question posed by the title of this book, aging is not a disease and diseases are cultural constructs used to define variants in the aging process.