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Durham University

Department of Anthropology


Publication details for Dr Malcolm T. Smith

Smith, M. T. (2001). Estimates of cousin marriage and mean inbreeding in the United Kingdom from 'birth briefs'. Journal of biosocial science 33(1): 55-66.

Author(s) from Durham


From 626 ascendant genealogies, known as ‘birth briefs’, deposited
by members of the Society of Genealogists in their London library, rates of
consanguineous marriage and coefficients of mean inbreeding () of offspring
were estimated for cohorts of marriages contracted in the late nineteenth and
early twentieth centuries. The rate of first cousin marriage in the generation
estimated to have married during the 1920s was 0·32%, with no marriages
between second cousins. The mean inbreeding coefficient for the offspring of
these marriages was estimated as 0·0002. In the previous generation 1·12% of
the marriages were between first cousins, and the estimate of mean inbreeding
was 0·0007. Comparison with data taken from the published literature
suggests that the levels of cousin marriage observed are consistent with a
secular decline during the late nineteenth and twentieth centuries.


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