But why couldn't genetic screening take care of that problem?
The authors of the NSGC study urge counselors to be "culturally respectful" of immigrant communities in which cousin marriage is "traditionally preferred." Why do these traditions promote cousin marriage?
You can't just say the practice in question is icky.
You have to state a principle and think through its implications. You can't appeal to Victorian morality; Queen Victoria married her first cousin.
Now a study by the National Society of Genetic Counselors says that having a child with your first cousin raises the risk of a significant birth defect from about 3-to-4 percent to about 4-to-7 percent.
According to the authors, that difference isn't big enough to justify genetic testing of cousin couples, much less bans on cousin marriage.
The greater the genetic similarity between your parents, the greater your chance of getting two copies of the bad gene.