Esmo wrote:
What evidence is there that the child of a close incestuous relationship will not have any greater likelihood of birth defects?
I'm sure I've read (somewhere?) that incest only increases the likelihood of birth defects by a couple percent. So, there is a greater chance, it's just not that much. However, I've never found any compelling studies about it (not that I've really looked), and it'd be a difficult thing to study anyway because I'm guessing family history would be a pretty big variable.
Studies aside, if you look at it purely by probability, then yes, the probability of birth defects or that even a "bad" recessive gene is passed on increases quite dramatically. But like I said before, defects might not actually start showing up until a few generations later, so one isolated case of incest may not be a big deal if their children don't have incestuous relationships.