Tired of hearing of these urban legends and popular opinions, I ask this question here to see if there really is scientific merit to this belief. My questions is, is it really "harmful" for a person to reproduce with his/her own first cousin? Everyone, at least in America, seems to think that this is incest which I completely dismiss because incest is purely a religious concept. The next argument I get is that we want more genetic diversity and having offspring with a first cousin is detrimental to our survival as a species. If you have any genetic weaknesses then your cousin is likely to be carrying them as well and then the chances of your offspring carrying them increase and so on.
I don't really believe any of this. It is rather well known (or may be not so well known) that only a very small percentage of a human individual is different from another human individual's genome. Differences due to skin color, race, ethnicity, and such are literally skin deep. So one reproducing with her cousin or someone half way across the globe is only negligibly different.
Forgetting about religion, has this been scientifically systematically tested and/or proven? Has any research been done on this? Is it true one way or the other? I don't mean to spark any debates here. Opinions are of course welcome. But if anyone can point me to any reputable sources or published results/references, that would be ideal.