Incest, the natural steriods of ancient times?

For some reason, upon reading the selections that were assigned and discused in class throughout this week, I began thinking about how all myths without fail and regardless of the purpose of the myth or the culture from which it originated, incorporate and embrace incest. Whether we see it among generations or gods or the two surviving mortals of an apocalyptic flood who "just happen" to be brother/sister... it's everywhere!! I guess what I find most interesting is the fact that in all mythologies throughout the ages, the product of two directly related gods usually results in a more powerful and dominant god or goddess when compared to a god that resulted from non-incestual parents... Horus (of the Egyptian myth "Osiris, Isis, and Horus") is a prime example recently looked into, his parents Osiris and Isis whom "loved one another from the time they shared their mother's womb" (pg 16, gross.) produced a very powerful warrior who goes on to rule Upper and Lower Egypt and become the intermediary between the living and the dead, pretty important guy. And don't even get me started on all the Greek/Roman gods, we all know that at least every other one of them is "their own grandpa". This prevelant motif throughout numerous cultures and ages leads me to believe that the people of these times viewed incestual relationships as necessary in order to produce stronger offspring, as modeled by their gods, why else would it be incorporated so frequently? I just find it rather comical that it was accepted so openly as common practice or at least something to look up to (since all their gods were doin' it), while in today's society it's viewed as absolutely taboo (illegal also, if I'm not mistaken..) and the offspring of such a union is viewed as genetically inferior or weaker... Food for thought!