Here is an article about Muslim inbreeding:
http://www.freerepublic.com/focus/f-news/3433495/posts
> "This practice [first-cousin marriage], which has been prohibited in the Judeo-Christian tradition since the days of Moses..." [quotation from the link]
I didn't recall myself, but had my doubts about it because marriage between first cousins was commonplace among the European aristocracy. Here's a link that specifies exact relationships along with Biblical passages, and concludes that the prohibition of marriage between blood relatives didn't include first cousins.
[Of course, if Adam and Eve were accepted as the ancestors of all of us, all of us would be blood relations -- natural selection too posits common ancestors -- but it would be a matter of where to draw the line in closeness of relationship.]
Though many other relationships were specifically forbidden in the Bible, that of first cousins was not. (Yet that would probably be one often brought into question in small-population ancient societies, so the silence on that probably indicates that it was accepted or, at least, tolerated.) "Conclusion:Scripture does not prohibit marriage between first-cousins."