Isonymy

This was reflected also in three types of measure of inbreeding: (1) close inbreeding recorded in ecclesiastical dispensations for marriages of relatives; (2) total inbreeding from pedigrees; and (3) inbreeding from marital isonymy.

The absolute isonymies calculated from them are given in Table 6, the relative isonymies in Table 7. Absolute and relative isonymies obtained from the remaining 1035 less common surnames are in Table 8 and Table 9, respectively.

Undoubtedly the most serious problem encountered in using isonymy data is “polyphyletism”: surnames often have multiple ancestral origins, which means that many isonymous marriage partners can be unrelated.

Our final test of the methods robustness is to make a direct comparison between the census evidence and the isonymy evidence about migrant origins.