As with gene data, knowledge of frequencies of molecular variants from human population samples helps in tracing population affinities, histories, diversification. Other applications of practical interest are at the individual level, mostly in a forensic context for identification of individuals. In addition to these, however, knowledge of individual DNA constitution may help to illuminate the more remote genetic history of populations, to show where their genes come from. This is illustrated by the example of Tristan da Cunha. The data are from the full report by Soodyall et al. (1995).

The population of Tristan da Cunha, a small island in the middle of the south Atlantic ocean, dates from the arrival there of a British garrison in 1816. During the course of its history, 15 women (Table 14.1, column 1) brought genes to the population, excluding those transient individuals who were shipwrecked and stayed on the island for only a few weeks or months before they could resume their journeys. Many of these genes were lost from the population as the women or their descendants died or left the island (Roberts, 1968), so that to the nuclear gene pool of the population of today (December 31, 1994) only seven women have contributed (Table 14.1, column 3).