Researchers at the deCODE Genetics company in Iceland combed through more than 150 years of data and found that "kissing cousins" produce more children and grandchildren than unrelated couples:
For women born between 1925 and 1949, with mates related at the degree of third cousins, the average number of children and grandchildren were 3.27 and 6.64, compared with 2.45 and 4.86 for those with mates who were eighth cousins, or more distantly related.
"These are counterintuitive, almost dislikable results," said Dr. Kari Stefansson, senior author of the paper on the study.
Dislikable, because our intuition is that the more closely related you are to your mate, the higher the chances of passing along the unfortunate traits so often associated with inbreeding.
Scientists are surmising that marrying your third cousin may actually be the best biological strategy for reproduction:
Now, many gene experts are scratching their heads while trying to explain the biological mechanism behind these results.
According to Stefansson, the reason that related couples were more biologically successful may be because these couples have "just right" genes when combined — not too similar, but not too dissimilar, either. [...]
"The take-home message is that ... we, as a society of [the] 21st century, have basically ruled against the marriages of closely related couples, because we do not look at it as desirable that closely related people have children," Stefansson said. "But in spite of the fact that bringing together two alleles of a recessive trait may be bad, there is clearly some biological wisdom in the union of relatively closely related people."