Since I'm not a biologist or a medical professional, I have to rely on the Internet. Here's a bit I found... "Inbreeding leads to a higher probability of congenital birth defects because it increases that proportion of zygotes that are homozygous, in particular for deleterious recessive alleles that produce such disorders."<quoted text>Can you cite a problematic outcome of a baby born from an incestuous relationship? Do you have any biology or medical references that describes the problems of incestuous births?
More likely, modern incest laws are based on biblical laws that prohibit incest in order to desexualize the home. That's why biblical law condemns inccest even in the case of adoption, where there is no close genetic relationship.
Another article states, "Doctors are worried about all close incestuous parings that result in a child, since such children have a much higher risk of disabilities."
Regarding incest and religion...
--According to most Biblical scholars, it is widely believe that Cain married his sister (since there were no other people on the planet).
--Abraham married his half sister Sara. They shared the same father, but not the same mother.
--Nachor (Abrahamís brother) married Melcha (his niece).
--Two of Lot's daughters got Lot drunk and had sex with him to preserve "the seed" of their father.
--Amram took to wife Jochabed his aunt by the fatherís side: and she bore him Aaron and Moses (so Aaron and Moses were the result of a marriage between their father and their father's aunt).
--Amnon, the son of David, fell in love with his sister, Thomar and had sex with her against her will.