The origins of the incest taboo are unclear, even after decades of careful study. one theory holds that the taboo exists as a result of the fear of biological degeneration and the possible effects of inbreeding. one of the arguments against this theory is that

One of the argument is that both genetics and population science emerged long after the incest taboo.
Despite all this, studies truly shown a strong correlation between an incentious relationship with defective genetics.
Infants that born through incenteous relationship are much more liekly to be less-intellectually developed and having lower immune system.

Lol that is s funny : )