Thursday, February 7, 2008

Want to have lots of children? Marry a third cousin!

Science Daily has an intriguing article dated 8 February 2008 - titled "Third Cousins Have Greatest Number of Offspring, Data from Iceland Shows." It summarizes a paper titled "An association between the kinship and fertility of human couples" that was published in the journal Science February 8, 2008.

The statistics show:

"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."

Isn't that interesting? The average number of children born to a union went down between 1824 and 1949, but the comparison held. Read the whole article.

Iceland has wonderful and nearly complete records and was pretty much a genetically closed society for a long time, so this is really a useful study to geneticists and demographers.

Now do you see why I'm looking for distant living cousins? I don't have any in Iceland, unfortunately!

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