Now this is interesting. Of course Abraham and Sarah were half-siblings, and most of the marriages recorded in the Old Testament were cousin marriages, the main consideration is what genetics you start out with. If you have a small group of people who in-breed who are of good genetic stock then there is not problem. However, if there are recessive genes that are dangerous they would be magnified in such circumstances.
BBC:
https://www.facebook.com/bbcthree/video ... 3MP0VhTQ8c
