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The records of 2600 marriages in Fylingdales Parish on the North Yorkshire coast of England, from 1654 through 1916, provide an opportunity to explore isonymic relationships. Since surnames are inherited like the Y chromosome, they are used to indicate inbreeding and migration. Combining like-sounding variants reduces the number of different surnames from 1330 to 968, and increases the coefficient of relationship somewhat. Dissection of total inbreeding into random and nonrandom, following Crow and Mange, shows the influence of isonymous marriages and the greater fluctuations over time of nonrandom and total, but the relative stability of random inbreeding, in this population. Coefficients of isonymy, following Lasker, show how occupation tends to channel gene flow over time. Cohesion is greatest for mariners and fishermen, while farmers, tradesmen, and laborers illustrate less isonymy over time. Parish boundaries also tend to channel gene flow. Lasker’s new Repeated Pairs of surnames, applied to these data, is influenced by the number of different surnames and by population size. Analysis of ethnic origin of identifiable surnames suggests that the majority are from Old English, 21% from French, 9% from German, 8% from Celtic, and only 7% from Scandinavian.