A note on the modifiability and reversibility of development and aging

Two major theories of biological development and aging are discussed: the mutation theory and the waste theory. The first relies on the instability of chromosomes and proposes that the aged organism, during his long life span, is more likely to have experienced damaging effects. Changes in irradiation have been introduced to manipulate longevity in the laboratory. The second theory relies on the accumulation of metabolic waste in cells and proposes, likewise, that the aged organism is more likely than the young to experience damaging effects. Recent developments in chemotherapy enable the removal of cellular waste material and, thus, the reversibility of aging processes. Some implications for the behavioral sciences are discussed.