theories of aging, theories proposed to explain aging and death of cells and organisms. They are generally divided into two major groupings. The first group consists of programmed causes, with timed functional changes, and is generally based on genetic theories; this group includes programmed senescence of cells, shortening of telomeres, and declines in hormonal or in immunological function. The second group, called stochastic theories, consists of theories based on random events occurring over time and includes free radical generation, gradual wear and tear, mutation over time, and differences in metabolic rate.
