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Inbreeding coefficients were calculated from the frequency of dispensations and from the frequency of isonymous marriages. The isonymy method reveals higher estimates of inbreeding than the dispensations do, probably because of polyphyletism. Both methods reveal similar secular changes in the estimated levels of inbreeding. The random and nonrandom components partitioned by the isonymy method, when supplemented by the historical information, enable an explanation to be put forward (although highly speculative) regarding the unusual mating patterns observed. Dispensations reveal that no first cousin marriages have occurred. Pedigree data reveal that dispensations may underestimate inbreeding.