I enjoy the quasi-medical and biological interpretations MJ. You really demonstrate for me how the Bible teaches lessons that are so holographic, that can be taught and learned on so many levels.
Simplifying my point; when I spoke of Abraham and Sarah's incest, being half siblings to a Jewish-studied qabbalist there was quite a reaction and defense. There is a lot of guilt there, actually, a cover up. The cover story being taught is that Sarai was Lot's daughter, not Terra's. A couple weeks of study though and it comes down to we really best accept what the Bible teaches, whether allegorical metaphor or not.
Myself, I believe that at about that time, we are at a juncture between history and metaphor as far as the actual people; but that the lessons are open to interpretation and in such are eternal in value.
So in persisting...
The question really comes down to allegorical or not, was Abraham half-brother to Sarah? Ancient papers tell that Sarah's mother was Tehevita and Abraham's mother was Yoni - both wives of Terra, their father.
The only reason to persist for me is that I feel the whole deal of sacrifice evolves around guilt. - Meaning that is what drove Abraham to putting a knife to Isaac's throat when he reached puberty.
The turtledove analogy is helpful but not backed by actual biology. The female does not lay male and female eggs. I looked briefly and find nothing about the in-nest monogamy too. But bringing that midrash into the discussion is very interesting indeed. Especially that this characteristic, true or not, makes the turtle dove an approved sacrifice.
The guilt of Abraham would also include that he allowed Sarah to murder Hagar, and dying of dehydration is horrific. But that the issue survived - Ishmael - to father twelve Arabic nations, always in conflict with the resulting decision to allow Isaac to survive the intended sacrifice is important symbology. What we can do here is remember that the Israelites were hard-hearted and stiff-necked too.
So I am undecided whether or not the whole sacrifice issue is about genetics or guilt?