During the twentieth century total loss of teeth has become prevalent in many countries, for example in New Zealand, in the United Kingdom and also in Finland. At age 65 and over more people have lost than retained their teeth in these countries. This situation does not, however, seem to represent the development originally intended by Nature. In a series of studies it has been possible to demonstrate that human teeth erupt with their supporting tissues throughout adult life. Between ages 43 and 65 years this eruption is only slightly slower than between ages 23 and 43 years. The purpose of this genetically predetermined eruption of human teeth seems to be to compensate for the natural wear of the occlusal surfaces and incisal edges. It seems that Nature has done its best. Why then have so many people lost their teeth in modern society? A review of the prevalence of, and the reasons for, edentulousness indicates that the total loss of teeth is historically closely related to rather rapid changes in dietary habits, combined with ignorance of prevention, unfortunate social circumstances and insufficient dental manpower resources at the right time in the right place. Against this background there is a great challenge to the dental profession to teach people how to care for their teeth and avoid needless destruction of the dentition by dental caries and periodontal disease.