The average human life expectancy has been increasing constantly since first observed in Roman Times (particularly during our century). This is usually believed to be related to such 'environmental' factors as sanitation and housing and to medical intervention. Data obtained from Vital Statistics of the United States supported the idea that these explanations are insufficient. Studies on persons who had died from conditions associated with advanced stages of arteriosclerosis (ischemic heart disease, cerebrospinal disease) showed the highest life expectancy. The inflammatory nature of arteriosclerosis and studies (by others) indicating 'protective' effects suggested that the developmental stages of arteriosclerosis (in contrast to the final stages) promote increased life expectancy. Inasmuch as certain viruses (especially the human herpes virus) are involved in the development of arteriosclerosis and because nearly everybody gets infected during childhood, this virus may be a factor in the increase of life expectancy. The work on symbiosis and on hormesis has established the fact that small amounts of parasites are often associated with beneficial effects for both the host and the parasites. All of this is in line with evolutionary expectations.