In the comments section, Cyrus points out that some ethnic groups do place priority on breeding within the group, particularly the Jews and the Armenians:
Robert, in addition to Jews having a fixation on non-intermarriage, I might also add that I have noticed this pattern with Armenians as well. Just an observation. Though, I believe there exists a social rational behind Jews and Armenians holding such views. A similar history of persecution, perhaps? A Near Eastern cultural element?
Yes, the Armenians and the Jews do want you to marry inside the group. And many immigrants to the West do too. I have noticed that with East Asians, there is strong pressure for Chinese to marry another Chinese, Koreans another Korean, Japanese another Japanese, etc. Even among SE Asians, there is pressure to marry your own. Khmer are pressured to marry other Khmer and not those horrible Lao or Viets, etc.
What’s funny is that marrying your own tribe can’t really be natural, since in order to keep it going, you have pound it into your people’s heads how evil the other tribes are. Most of these accusations against the other groups are simply lies. So the only way to prevent mass miscegenation is with mass lying propaganda. Doesn’t sound like an inborn trait to me.
If you study tribes, it’s clear that most totally don’t give a fuck about genetic purity. I studied Amerindian tribes, and it was quite common to take a wife not just from another village, but even from another tribe. She left her tribe and came to yours, abandoned her language and culture and adopted yours, and she was automatically one of your people. It also makes sense from a genetic POV, as you are avoiding becoming inbred. It seems that primitives had some understanding of genetics after all.
Further, tribes have always conquered other tribes and raided them to steal their women. One thing you can do is raid the other tribe and rape all their women to force them to bear your genetic line. Or bring the women back to your tribe and breed them in with your tribe, and extinct their tribe in the process.
Primitives did not understand genetics very well, but clearly there was a prerogative to keep the tribe going and in many cases to wipe out the competing tribes. By kidnapping their women, bringing them back to your village, and making them bear your kids, you extinct their tribe while incorporating their genes into your own line.
Any group doing this cares not one whit about genetic purity. They just mass-miscegenated with the enemy! Come on!
However, they did keep their tribe going and extinct a competing tribe. These tendencies may well be genetically driven.
Kevin MacDonald says that humans have evolved traits to do two opposite things:
1. Guard the women of your own tribe from breeding with enemy or competing groups.
2. Conversely, the men have a drive to breed with the women of the competing group (in addition to breeding with their own)!
Maybe this is not so contrary as it seems. Women are the seed stock of your tribe. When they are gone, you are gone. You need to preserve them from the enemy taking them out and extincting your group. On the other hand, by stealing the enemy’s women, you weaken them, force them to carry your line, and possibly wipe them out altogether.
The result is the imperative in the title: Safeguard Your Own Women, Steal the Enemy’s Women.
All makes sense from a group competition POV.