title: The structure of the human population of the Isles of Scilly: inferences from surnames and birthplaces listed in census and marriage records.
abstract: Investigation of the commonality of surnames among the isles of Scilly using data covering the period from 1726 to the present, yields coefficients of relationship by isonymy which are compared with measures of relationship based on marital migration rates. The coefficients of relationship, calculated from lists of surnames in the marriage registers, and from lists of male surnames from the 1851 and 1871 censuses, are higher than any values yet reported for other British populations. However, the coefficient of relationship between the islands as a whole and the mainland of England and Wales is similar to the values reported for other English populations. Comparison of coefficients of relationship by marital isonymy show an overall decrease in the frequency of such marriages over time and a slight tendency to avoid marriages between close relatives. The lack of correlation between coefficients of relationship by random isonymy and marital migration rates derived from the census data is believed to be due to fluctuations in marriage patterns over time, the marital migration rates accounting for single generational patterns, while the coefficients of relationship by isonymy reflect the accumulated breeding structure. The chief influences on the coefficients of relationship appear to have been the founder effect, coupled with a long history of inter-island marriage but a high rate of endogamy from the islands as a whole.
mesh_terms: D004739:England; D005260:Female; D006801:Humans; D008297:Male; D008393:Marriage; D009275:Names; D011157:Population Dynamics; D013997:Time Factors