When Incest Is Best: Kissing Cousins Have More Kin - Scientific American

When Incest Is Best: Kissing Cousins Have More Kin - Scientific American:

It is not quite incest. And though it will increase your chances of birthing a healthy baby, it is a bit unorthodox, to say the least. Still, scientists at Icelandic biotechnology company deCODE genetics say that when third and fourth cousins procreate, they generally have scads of kids and grandkids (relative to everyone else).

It's interesting that the canon law of the Orthodox Church prohibits marriage between second cousins or people more closely related, which means there could be quite a lot of third-cousin marriages in small isolated Greek villages, for example.