Thursday, July 7, 2011

Pruning the Family Tree

Did you know that implexion is the term for the ‘pruning’ of a family tree in earlier generations? Coined by  Cecil Humphery-Smith OBE over fifty years ago, to describe why we do not have more ancestors than the world’s population at that time, it simply means that an individual can appear in more than one position in the tree.

Robert C. Gunderson also called it ‘Pedigree Collapse’. In twenty generations, an individual would have 220 ancestors, but the more generations back, the less likely it is that there were enough people alive - unless some of them were the same. Instead of a binary tree, the result of pedigree collapse is a directed acyclic graph. Many genealogists find cousin marriages in their trees, often to such a distance that the couple themselves did not know they were related, yet it reduces the number of ancestors in the tally.

The effect can be particularly strong in isolated communities such as islands, persecuted communities, and within royal families. Indeed, some members of royal families, such as Alfonso XII and Charles II of Spain, have been shockingly inbred, to the extent that Charles II was likely to have had more copies of the same genes from each parent than if they had been brother and sister. That resulted in genetic disorders because there was no ‘good’ copy of a gene to counteract the ‘bad’ copy. For the rest of us, of course, pedigree collapse is a natural phenomenon that has no harmful effect- beyond depriving us of the occasional branch to hunt.

[Extract from IHGS Newsletter July 2011]

Queen Victoria's family tree

Queen Victoria, who married Prince Albert of Saxe-Coburg and Gotha, was the last British monarch of the German House of Hanover. Her son, King Edward VII, belonged to the same line as his father. Victoria was also the grandmother of Princess Victoria of Hesse and by Rhine. Hence, she is the great great grandmother of both Prince Philip and Queen Elizabeth II.

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