That may be true, but it is also known that “blood mixing” has very good results, gene wise. For example, it was common among eskimos to let their wife have sex with a complete stranger (someone who somehow stumbled upon their community/home and is currently staying as a guest). Why? Because they noticed that there are very few of them out there and that inbreeding produces… well, mentally challenged people. They noticed that this doesn’t happen when the child is of someone from outside their community. In fact, it has traits that might make him/her stronger, smarter, less prone to illness, etc. So, this became a custom. Whenever a stranger showed up, people were very welcoming and they (more or less) fought over at which home the stranger would stay at. It was also not uncommon for the stranger to stay at several homes (one after another) during his stay.

We also had this incentive in ex Yugolsavia. Military service was mandatory and soldiers were sent to serve as far away as possible, to other corners of the federation, especially places with mixed ethnicums/religions. Why? So they would meet a local girl and possibly marry. You can’t have an ethic/religious war if you’re Bosnian, but your husband is Serbian 😉. This is why the war in Bosnia was so hard on the local population and a lot of families migrated just to avoid being caught by one side or another. They had a life, a family, regardless if they or their wife is muslim or christian 😔.