The demography of Tristan da Cunha

The eruption of the volcano on Tristan da Cunha in 1961 and the subsequent arrival of the island population in the United Kingdom provided a unique opportunity for studying the health of this formerly isolated community. During their stay, while the facilities and services of modern medicine were made available to them, investigations of many facets of their general biology were made under the auspices of the Medical Research Council, co-ordinated by Dr. H. E. Lewis. Analysis of their demographic history was essential to understand many features of their disease pattern, and the results of this analysis are presented here. They are of interest in that they not only show some consistent trends in the common variables of demography, but also demonstrate biological principles, some perhaps for the first time in man, which may be fundamental in the process of colonization as a biological phenomenon, e.g. the initial difficulty of establishment of a population in a new area, the curious demographic structure that may emerge in its earliest years, the bottleneck effect of population-size reduction, the founder principle.