An Attempt to Integrate Previous Localized Estimates of Human Inbreeding for the Whole of Britain

Abstract There have been a number of previous estimates of human inbreeding for Britons of British descent in Britain; each generally for different social classes, geographical regions, and/or time periods. In this study an attempt was made to collect all relevant published studies and to combine the results of these disparate studies into an integrated whole for all of Britain. This was achieved by combining weighted means of the percentage of consanguineous marriages (f%) reported in these earlier studies: weighted according to the number of records each author examined, the proportion of social classes or geographical regions covered by the records, and the ‘merit’ of their individual research methodologies. The percentage occurrences of the various consanguineous marriages, from 1st to 3rd cousins, were partitioned into a number of time periods, which allowed the weighted mean percentage inbreeding coefficients (F%) to be obtained as a function of time over the period from 1820 to 1960. The resulting temporal scatter distribution of the weighted F% values closely followed a sigmoidal curve, with a non-linear correlation coefficient of η = 0.974, which fitted well to a generalized logistic function. After about 1900 the value of the weighted F% was essentially constant at about 0.038±0.004, whereas it decreased rapidly from about 0.256±0.011 between 1820 and 1900. The upper-bound value of weighted F%, before 1820, from the fitted logistic function is 0.276. Note that this corresponds to a value of the conventional mean inbreeding coefficient F = 0.00276. As the first known attempt to integrate the earlier disparate values of unweighted F% for Britons of British descent for all of Britain, the results of this analysis are promising and should be useful as reference values in other related studies