@john65pennington – Seriously, again – dogs are inbred over generations and that’s the problem with pure breeds.
As stated above by @markferg, but to emphasize – in April 2002, the Journal of Genetic Counseling released a report which estimated the average risk of birth defects in a child born of first cousins at 1.7–2.8% over an average base risk for non-cousin couples of 3%, or about the same as that of any woman over age 40. In terms of mortality, a 1994 study found a mean excess pre-reproductive mortality rate of 4.4%,
But finally – reproduction is not an essential element of marriage. There are plenty of people young and old who get married with no or uncertain intentions about having children.
It just seems like a pointless regulation at this time in our history.
And again – cousins who want to have sex are gonna do it, regardless of the ick factor for some. Marriage doesn’t PREVENT those who don’t marry from reproducing.
Let’s just note that there are 20 states or so that allow first cousins to legally marry. Have we had rampant instances of first cousin married sex babies with developmental problems?
PS – I do not mean to sound confrontational on this one…I know you might simply be answering the OP’s initial question with your opinion about what the legislation was initially for.