If you live in Pennsylvania, it's West Virginia. If you live in California, it's every 'red state' in the Union. No matter where you live, some nearby state is the butt of inbreeding jokes.
Well, those places you make fun of for having an evolutionary tree that's a straight line are also having the last laugh, it seems.
In a new paper, deCODE scientists establish 'a substantial and consistent positive correlation between the kinship of couples and the number of children and grandchildren they have.'
Counterintuitive? Sure, from an evolutionary perspective closely-related parents have a higher probability of having offspring homozygous for deleterious recessive mutations, but closer parental kinship can also decrease the likelihood of immunological incompatibility between mother and offspring, for example in rhesus factor blood type.