Effect of the XXXX on inbreeding in 14th century Britain.

@entity1407 @entity195
The purpose of the study reported here was to further investigate a new method of estimating inbreeding in large, relatively isolated populations over historic times, as reported by Pattison (1999, 2001). The method is based on modeling the genealogical "paradox" and produces values of Pearl's coefficients of inbreeding as a function of time for any given population curve. In particular, this study demonstrates that the new method of estimating inbreeding may be used to examine the effect of unusual features in population curves on levels of inbreeding in that population. As an example, the medieval population "bump" that spans the 13th and 14th centuries in the population of Britain, which terminated abruptly with the outbreak of @entity1407 in 1348 @entity195 , is examined. It is first assumed that the whole population was the adult (breeding) population, corresponding to minimum inbreeding. For this case it is found that, for distant generations, about 90% of the whole population occurs in any present-day British pedigree. This value compares favorably with the values of 85% and 80% reported by Wachter (1980) and Derrida et al. (1999, 2000), respectively. The population bump causes the curves for Pearl's coefficient, for minimum inbreeding, to have a plateau of about 96% over the period from about 1220 @entity195 to 1380 @entity195 . The effect of introducing a single known estimate of inbreeding into the model is to produce a more realistic situation where the adult (breeding) population is considerably less than the whole population. It is found that the maximum number of different ancestors in any generation, in the average British pedigree, is about 22900 individuals and occurs about 1220 @entity195 . More importantly, and possibly contrary to expectation, it is now found that the population bump had virtually no effect on the level of inbreeding.
