deCode discovers cousin marriages bear more offspring
deCode has analysed its 200 year old Icelandic genealogical database and found that the closer the kinship of the couple the more children they are likely to have. This study provides the most comprehensive answer yet to the longstanding question of how kinship affects fertility in humans.
For example, for women born between 1800 and 1824, those with a mate related at the level of a third cousin had an average of 4.04 children and 9.17 grandchildren, while those related to their mates as eighth cousins or more distantly had 3.34 children and 7.31 grandchildren. For women born in the period 1925-1949 with mates related at the degree of third cousins, the average number of children and grandchildren were 3.27 and 6.64, compared to 2.45 and 4.86 for those with mates who were eighth cousins or more distantly related.
The findings hold for every 25-year interval studied, beginning with those born in the year 1800 up to the present day. Because of the strength and consistency of the association, even between couples with very subtle differences in kinship, the authors conclude that the effect very likely has a biological basis, one which has yet to be elucidated.
Previous studies in other parts of the world have suggested that the two phenomena are positively correlated, though confounding variables, such as the impact of socioeconomic status on the size of families or age at marriage, have made the results difficult to interpret.
The authors note that the findings are somewhat counter-intuitive from an evolutionary perspective because closely-related parents have a higher probability of having offspring with severe genetic abnormalities.
For further information, click on:
http://www.decode.com/News/2008_02_07.php
Elaine Warburton www.geneticsandhealth.com
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POSTED IN: Chromosome abnormalities, DNA, Evolution, Genealogy and DNA, General Genetics and Health, Genes, Genetic Ingenuity, Genetic Testing, Genetics of Disease, Human Genome, Population genetics, chromosomes
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