Fascinating topic. And it is one I've thought much about of late. I'm ending my day but just wanted to make some quick comments---and admit that I've not carefully read the entire thread. {And I want to thank all of you for such thought-filled comments that were a delight to read and think about. So even the ideas with which I disagreed were a blessing to me---obviously because they came from my brethren in Christ who share a reverence for the Biblical text}
With that in mind, I decided to start with Caliminian's comment, just to have a place to begin:
In scripture, divine sonship comes via direct creation by God. If these sons of God were descended from other pre-Adamic creatures, they are still not direct creations and therefore could not be called sons of god.
I applaud your willingness to integrate the entire Bible as the word of one Divine Author but it is also 66 books from many authors over many centuries in three languages. Should we assume that every term in the Bible has a single meaning and/or pedigree? Unlikely. [Note that the asterisks below serve as a footnote reference, all to be found at the bottom of this essay.]
What "rule" in scripture says that "Sons of God" MUST be "direct creations"? **
1) Words, no matter what language we are talking about mean whatever the speakers assign to them. Somebody could decide to call their racehorse "Sons of God" or their award-winning variety of tea-rose "Sons of God". And no, those are NOT absurd examples. It is basic linguistics and I'm making a key point.
2) Why would anyone assume that the phrase "Sons of God" in ancient Hebrew was at all impacted/governed by what "Sons of God" would mean in the Greek New Testament? (Surely nobody is going to say that there is some kind of "divine standardization of terms" that would revolve around the English language, especially when they realize that the SEMANTIC DOMAINS of the Hebrew words and the Greek words are quite different!)
3) And although "Sons of God" and "Daughters of Men" appear in the Hebrew Masoretic Text as if they had been Hebrew terms from the time of their "origins", we don't know that! We have no idea what the phrases would have been in terms of whatever the language was at the time of the events described. Those events could have been MANY thousands of years prior to the EXISTENCE of the Hebrew language! And we don't know HOW the original terms in their original language got transformed or translated to Hebrew and how....and perhaps over a SERIES of intermediate languages! And we don't even know if those portions of the Book of Genesis were passed down to Moses as scrolls from centuries before *or* had been retold as oral histories (also over the centuries of multiple languages.)
4) Accordingly, we know MUCH LESS about the context than anybody here has posited as possible---even though enormous gaps are LIKELY.
Therefore, I suggest we consider the terms to be "wide open" and WITHOUT the blinders of TRADITION (which so often confuse our ability to read the Bible on its own terms.)
So I won't presume to know better than the ancients HOW they used those phrases AT THAT TIME AND PLACE IN HISTORY. But for a great many linguistic and scientific reasons, including what we KNOW about genetic bottlenecks and evolutionary processes [yes, we can and do KNOW them, despite my "lost years" as a dedicated young earth creation activist/speaker], I have thought about the following:
"The daughters of men" became a phrase associated with female descendents of Adam, the IMAGO DEI-endowed Homo sapiens [or should we use the term
Homo sapiens sapiens?].
"The sons of God" became a phrase associated with a "super race" of hominids who were larger, stronger, and faster than the Adamic men. [And by the way, the term "Sons of God" could easily have been applied to an entire people (or should I say "creature") regardless of gender. After all, it is common in many cultures, both ancient and today, for a people to be called by a name which, technically, applies only to males. And many language units work that way, such as Hebrew ADAM in Genesis refers at times to a male adult and sometimes to humans in general; and in English "man" also means "mankind" which includes females; and in German "man" means "one [person]" regardless of gender.]
If a genetically bigger, stronger, taller, faster male from the "Sons of God" tribe [and wouldn't "sons of God" be appropriate for someone of such a superior stature, especially if a fearsome sight?] married a "daughter of men" [an average human], is it not likely that the impressive HYBRIDS might grow up to be MEN OF RENOWN (also a "proper name" eventually, even used as a royal title.) So at that time, the phrases became the obvious ways to refer to the Adamic tribe vs. the non-Adamic tribe, the "regular humans" versus the "Giants"/"Sons of God". [In associating them with "God", it wasn't a reference to HOLINESS or RIGHTEOUSNESS or WISDOM; it would have referred to AWESOME, GIGANTIC, INTIMIDATING, and OVERWHELMING. "Sons of God" makes sense in the same ways that the Greek and Roman PANTHEONS of gods and goddesses made sense!]
An objection to all of this by some would be because of their TRADITIONAL assumption that God has "planned out" every term of the Bible in a systematic way so that a well-structured "lesson plan" is revealed in scripture. Yes, in many ways I agree. But that doesn't mean that the individual WRITERS of the Bible didn't use the terminology of their time and place in human history. "Sons of God" had a particular meaning for the time and place of the "pre-Noah" account. The author used the terms "sons of God" and "daughters of men". [We might wish to put them in Capital-letters to suggest they were "proper nouns" as in the names of TRIBES (for example)---even though the written language had no provision for upper-case, obviously, and we are only speculating. BUT WE MUST LEAVE OPEN ALL SUCH POSSIBILITIES if we are going to let the text speak for itself!]
Now consider this: Why is there a strange interlude about "giants" and "Men of Renown" just before the Noah account? Isn't it likely that it sets the stage for God's judgment of the ERETZ (the "land")? And consider this: Suppose the Lineage of Adam (the only creatures with the IMAGO DEI, the Image of God endowed upon them) had been commanded NOT to intermarry with the SAVAGE, VIOLENT, SUPER-SIZED brutes of hominid creatures. [Homo Neanderthal? Probably not, but I just want to shape up our thinking to allow possibilities.] After all, there may have been no GENETIC reason that the two "tribes" could not produce young. But only the Adamic line was blessed by God with the purpose and ABILITY to relate to the Creator as Adam and Eve had done in the Garden. But biology is biology and the "Sons of God" would have been appealing to the "Daughters of Men", because such big and powerful men would have been able hunters and superior warriors and defenders! (And that would appeal to human father-in-laws as well as their daughters.)
So despite prohibitions of intermarriage, the two tribes DID mix---and the hybrid young would have inherited the savage violence and ruthless traits of the fathers. But notice that Noah "was pure in all his generations". Now that is a debated structure and I'm not entirely convinced that that "pure race" interpretation is the best, but suppose it is saying that ONLY NOAH had a PURE ADAMIC LINEAGE. And that purity of lineage may have also meant that the IMAGE OF GOD within him called him to a right relationship with God and an attitude of FAITH and REPENTANCE for his sins---attributes missing among the people after generations of mixing.
This "theory" solves a LOT of the genetic bottleneck issues of Noah's family being the ONLY genetic sources for the entire human population today. Because AFTER the flood ---because the Hebrew Text of Genesis shows NO evidence of a GLOBAL flood [I don't say that casually after much study] and therefore non-Adamic hominids would have survived OUTSIDE of the region where the Adamic lineage had lived and was completely destroyed except Noah's family. So, yes, after the Flood, genetic mixing happened again.
There are many other aspects of the theory which I could address for many pages----but I must sleep. And for now I mainly wanted to emphasize this: "Sons of God" and "Daughters of Men" were at that time and place in human history the TRIBAL NAMES of the Giants-versus-the-Normals, or the Brutes-versus-the-Civilized-Ones. They were not special names chosen by God to teach us some profound truth. So let's not theologize them. That simply doesn't hold up to basic linguistic scrutiny.
Years ago I thought of publishing a paper on this but I've gotten the impression from things said in passing at some theological conferences as well as a few footnotes in books that if I looked a bit, I would probably find this very "hypothesis" expressed by multiple evangelical authors. It HARMONIZES with both the scriptures and the science. And that is all I'm saying at this point. My goal is to consider all of the POSSIBILITIES of the text rather than simply champion whatever TRADITIONAL interpretation I might have been raised in.
But I can also say that we should DISMISS and put to rest the tired old tradition of the "Sons of God" being ANGELS. The fact that that term appears LATER in Biblical history does NOT justify anachronisms in Genesis 6. And Jesus said, "The angels neither marry nor are given in marriage", which loosely paraphrased means, "The angels don't reproduce sexually as males ["to marry"] or females ["to be given in marriage".] And I'm tempted to add to the paraphrase: "you simpleton!", because I think Jesus was being very emphatic there and was chiding the Pharisees for such a silly idea, as if he were saying, "obviously!". So let us throw that interpretation in the dustbin of hermeneutics.
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FOOTNOTES:
** Indeed, how do we know that "HADAM" ["the human one", "the red-soiled human", both male & female, "Adam & Eve"] was a "direct creation"? They were certainly a UNIQUE creation in being endowed with the IMAGO DEI. But Genesis 2:7 only states that God formed HADAM from "the dust of the ground", that is, the basic chemical elements of the earth's crust. So we know the starting ingredients and the end product---but neither the time period involved NOR the number and nature of the intermediate processes. The major theme of Genesis 1&2 was "God did the creating!" We don't get much information about the physics and chemistry processes that God used. We have no reason to make assumptions about "direct creation". Indeed, HADAM wasn't created through the special creation of EX NIHILO, that is for sure! We only are told of the intermediate process involving "the dust of the ground"---and therefore, who knows how much EROSION OF ROCK was needed to produce that dust. And let's not get distracted by "appearance of age" and "embedded age", neither of which are mentioned in the Genesis text.