22 March 2009

Prohibited degrees of kinship and autozygosity

The Table of Kindred and Affinity in the Church of England's Book of Common Prayer was probably one of the early influences responsible for my interest in family history. According to Wikipedia the table states that:

A Man may not marry his mother, daughter, adopted daughter, father's mother, mother's mother, son's daughter, daughter's daughter, sister, wife's mother, wife's daughter, father's wife, son's wife, father's father's wife, mother's father's wife, wife's father's mother, wife's mother's mother, wife's daughter's daughter, wife's son's daughter, son's son's wife, daughter's son's wife, father's sister, mother's sister, brother's daughter, sister's daughter.
A Woman may not marry with her father, son, adopted son, father's father, mother's father, son's son, daughter's son, brother, husband's father, husband's son, mother's husband, daughter's husband, father's mother's husband, mother's mother's husband, husband's father's father, husband's mother's father, husband's son's son, husband's daughter's son, son's daughter's husband, daughter's daughter's husband, father's brother, mother's brother, brother's son, sister's son.
Figure all that out and you've learnt a lot about family trees.

I don't recall that the reason for these prohibitions was explained to me. Perhaps vague talk of the dangers of inbreeding.

This came back to me, although not the detail, while reading, or attempting to read, the article Measures of Autozygosity in Decline: Globalization, Urbanization, and Its Implications for Medical Genetics published PLoS Genetics.

It shows that for two groups of Americans of European origin their DNA exhibits more genetic diversity the younger they are. As they put it, genetic changes occurring over the past century ... have been likely brought about by recent increases in mobility, urbanization, and population admixture. This "may help to slightly reduce the burden of rare recessive diseases in the future."

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