The pseudo-genetic analysis of given names shows that, in the Scilly Isles, coefficients of relationship of first names are similar on St Mary's, the Outer Isles, and in the total sample of 5666 individuals married there in two and a half centuries. Comparable coefficients of relationship of a sample of 1658 given names in marriages in England and Wales in 1975 are considerably smaller, but similar within and between districts. The coefficients of relationship of given names on the Scilly Isles decreased during the 19th and especially the 20th centuries in parallel with decreases in random relationship from surnames. The genetic versus cultural–linguistic factors cannot be distinguished in the temporal variation in names, but the geographic differentiation virtually always reported in surnames is not present in these examples of given names and the geographic pattern in the surnames thus seems to result from the hereditary aspect of surnames. This result supports the validity of use of surnames in models of human genetic geography.