Women who are *forced* into marriage as teenagers, who aren't allowed to finish high school or go to college, who are traded like cattle in these Islamic or tribal African countries have high birth rates. As soon as women are educated and *free* to reject marriage if they wish, or where marriage itself gets reformed so that their husbands don't treat them worse than the camels or goats, then family sizes decrease.
You can prove this to yourself by looking at the fertility and birth rates of countries in the 2001 CIA World Fact book. EVERY country that is on the road to civilizing itself has lower fertility AND birth rates than countries in which women are still brutalized and traded like animals.
This is considered an extremely politically incorrect assertion by the "right," because it goes against a particular conservative fantasy of a return to six and seven children per family. While there will always be a small percentage of people in the civilized countries who will *choose* to have large families, the general pattern seems to be that if women have the choice not to marry, or not to have large families if they do marry, that most will choose not to. In other words, to ensure a high birth rate on a population basis, you have to force women into it. This is what *conservatives* are going to have to deal with, rather than indulging in nostalgic 19th century fantasies, and I say this *as a conservative.*