Cancers are different diseases that start and evolve each in its own manner, and trigger variable responses from the organism depending upon the neoplastic process under way and upon the physiopathology of the organism. The clinical incidence of the different cancers is spread through the human life span, with regional differences for each cancer: for many cancers the incidence is increasing at younger ages. More than half of the cancers become clinically manifest during the second half of the human life span and their frequency increases with age, but their natural history starts way back at earlier ages. The data suggest that the late manifestation is the result of the accumulation of events through time rather than of aging. Interestingly, late in the human life span the incidence of neoplastic disease declines. Is this due to the cohort of late survivals naturally resistant to the development of neoplastic processes, or to the characteristics of the last 'window' of the human life span? The evolution of neoplastic disease is the result of pre- and postnatal aggressions suffered by the organism, individual susceptibility, and developmental changes that evolve continuously from the beginning to the end of the human life span. The identification of the causes of the incidences of the different cancers through the human life span will help to understand both neoplastic disease and aging of the organism.