Inbreeding is not deleterious in and of itself, except when it concentrates deleterious recessive traits. However, over time, these traits wash out. Advantageous recessive traits do not. Examples of successful sustained inbreeding in humans include the Egyptian Pharaohs. In other mammals, you have the Naked Mole Rats, which are eusocial and where the queen breeds with her offspring, with no ill effect.
In any case, this is not totally relevant to us, because in our society, cousin marriage is combined with a steady inflow of converts.
For instance, the tribe of Judah is descended from Tamar, a Canaanite woman. Joseph married Asenath, a Egyptian noble girl, and the tribes of Ephraim and Menashe come from her. Moses married Tzipporah, who was either a Midianite or a Kushite. The Davidic dynasty comes from Ruth, a Moabite convert. Etc., etc.
Your Pakistanis are not Semitic but Aryan, by the way. Cousin marriage is also practiced in Iran, and has been from the time of the Ancient Persians, and is common among Hindus. So you might as well refer to it as a "despicable Aryan practice"
The mentality of Abraham, who sends Eliezer to find a wife for his son, is not "find him a hot wife." This is the normal thinking in a society of sexual anarchy, where people mate like wild dogs coming together, i.e., the modern West. You should not project it onto our patriarchs, who were completely different people living in a different time with a different mentality. In a normal, functional society, this is not how things are done. You look for a good family, if possible (Abraham didn't have this option,) and good character traits. When you put people together who are generally compatible, and their marriage is a fait accompli, they learn how to love each other with the years. Notice that when they were married, Isaac was 40. When a man marries late, he does not look for the same things that he does when he marries early, and in any case, Isaac was subject to his father's authority in all aspects (notice how his life was an almost complete parallel of Abraham's).
Thanks for your response, I was hoping you would chime in. I appreciate your comments on marriage in a more holistic patriarchal context.
I should have credited Moldbug for the inbreeding comment, but I was trying to draw you out and it worked. I am over 13% Ashkenazi myself, and grateful for the admixture, granted to me by my great-grandmother who was trafficked by fellow Jews to the remote tip of South America as a burlesque dancer and prostitute. Her village in Eastern Europe was later targeted for a pogrom, so I guess it worked out after all. August beginnings!
Pakistani Muslims tend to be either conquered Hindus of any caste, or else converted members of the lowest castes, seeking social equality as Muslims. I don't know what kind my neighbors might be, but the level of inbreeding is staggering. It takes a long time and a large population to wash out deleterious genes, the Paki's aren't there yet, obviously. Hindus are highly endogamous within their castes but not so much into cousin marriage, the rampant inbreeding among Paki's has to be the Muslim/Arab (hence Semitic) influence I think.
Thanks again, Baruch, hope to hear from you more.
(c) 2017 Lynn Lockhart & Baruch Kogan