When people began to multiply on the face of the ground, and daughters were born to them, the sons of God saw that they were fair; and they took wives for themselves of all that they chose. Then Yahweh said, 'My spirit shall not abide in mortals for ever, for they are flesh; their days shall be one hundred and twenty years.' The Nephilim were on the earth in those days—and also afterwards—when the sons of God went in to the daughters of men, who bore children to them. These were the heroes that were of old, warriors of renown.
This may be surprising to even veteran students of the bible, but the Israelite concept of what 'gods' were was looser in the tenth century BC than it is now. So although Israelites followers of Yahweh God are often subject to modern criticism as being 'polytheists', it technically is true, depending on how we're using the word 'god'.
In the previous article, we determined that the reading of this passage most sensitive to context, language, and history is the one which accepts that the 'sons of God' refers to the creatures we usually call angels; in this case, a specific class of angels Second Temple-era Judeans calls 'the Watchers'. We also saw that other biblical passages call angels terms like 'the heavenly host', 'stars', 'spirits', and… 'gods'. The very epithet 'sons of God' (bene elohim appears to have been appropriated by the ancient Israelites from their Canaanite neighbors, where it originally referred to a category of lesser gods called the 'sons of El' (bn ʾil).
Meaning, within the Israelite worldview, angels — powerful, human-like beings who reside in heaven, but nevertheless had been created by the supreme God Yahweh — could be called 'gods' unironically. Given that the story in Genesis 6.1-4 is only three sentences long, we can be certain there was once a larger tradition behind it. (The detailed account found in 1 Enoch 1-36 is not a reliable representation of how Genesis 6.1-4 was originally understood by its author. Instead, it is an expansion, albeit very early, based on Genesis 6.1-4.) Still, with the information we can glean from the existing text, we can recognize the story for what it is: a myth of gods producing offspring by human women.
What, then, were the children of these unions, the Nephilim? They were demigods, humans born with extraordinary natural prowess for combat. The first translation of Genesis was written by Judean authorities for the Greek-speaking Judeans. Here, they chose to translate 'Nephilim' as the word gigantes, 'Giants'.
There is no direct parallel in Canaanite religion, but broader Mesopotamian culture does have stories of demigods born from the unions of gods and humans.
In the Gilgamesh Epic we are told that "two-thirds of him is god and one-third of him is human" (I.46 and IX.51), the son of the goddess Ninsun and the human king Lugalbanda. In this ancestry we see a divine/human marriage and the birth of a semidivine child. […] the Tukuli Ninurta Epic describes the Assyrian king as "the flesh of the gods" (šēr ilāni), the same phrase used to describe Gilgamesh in Gilg. IX.53. […] It is entirely possible that the unknown legends of the Nephilim have something to do with stories of such ancient semidivine warrior-kings.
Hendel, 'The Nephilim Were on the Earth',
The Fall of the Angels, 28
The angelic parentage of these Nephilim would explain their destiny to become 'heroes of old, warriors of renown'. The word Nephilim, it is argued, comes from the Hebrew verb 'to fall', as in warriors falling in combat.
Faced with the prospect of annihilation in battle, the doomed Pharaoh and his army are mockingly consoled by YHWH: when they descend into the netherworld, they will enjoy the company of warriors from every nation "fallen by the sword" (הנפלים בחרב). [Ezekiel 32.22-24] But these war dead compare poorly with the fallen warriors (גבורים נפלים) "who descended to Sheol with their battle-gear, and whose swords were given under their heads, and whose shields are upon their bones" (32:27).
Chris Seeman, 'The Watchers Tradition and Gen 6:1-4',
The Watchers in Jewish and Christian Tradition, 32
However, there is a severe problem in the narration here: the Nephilim survive the flood. As the text states, 'The Nephilim were on the earth in those days [before the flood]—and also afterwards'. How could this be, since the flood narrative very emphatically says every creature that lives on dry land was killed if it was not on the ark?
And all flesh died that moved on the earth, birds, domestic animals, wild animals, all swarming creatures that swarm on the earth, and all human beings; everything on dry land in whose nostrils was the breath of life died. He blotted out every living thing that was on the face of the ground, human beings and animals and creeping things and birds of the air; they were blotted out from the earth. Only Noah was left, and those that were with him in the ark.
Whatever the means of their mysterious survival, the Nephilim do appear in the world after the flood. Right off the ark, the very first implication that the Giants survived the flood is Genesis 10.8-12 with the person of Nimrod. The Hebrew text calls the Nephilim gibborim (heroes) and anse ha shem (warriors of renown). Nimrod is likewise called a gibbor (hero). As noted above, the Greek calls the Nephilim gigantes (Giants); Nimrod is also called a gigas (giant).
Much later, when the Israelites escape Egypt, they send spies into the land of Canaan. The spies scope out the Five Cities region, where they see a tribe of intimidatingly large men:
The land that we have gone through as spies is a land that devours its inhabitants; and all the people that we saw in it are of great size. There we saw the Nephilim (the Anakim come from the Nephilim); and to ourselves we seemed like grasshoppers, and so we seemed to them.
With this inexplicable reappearance of the Nephilim, the biblical narrative forges an obscure trail where the Nephilim's distant descendants keep showing up: The gigantic Anakim are descended from the Nephilim (Numbers 13.33), the gigantic Rephaim and Emim are related to the Anakim (Deuteronomy 2.10-11), the Rephaim took part in the War of Nine Kings (Genesis 14.5), the gigantic King Og of Bashan was one of the Rephaim (Deuteronomy 3.11), the Philistines lived in the Valley of the Rephaim (2 Samuel 5.18), and the gigantic Goliath and the other Philistine heroes killed by David and his elite warriors were Rephaim (2 Samuel 21.15-22). These men and tribes are consistently described as physically huge, standing several feet taller than the people around them, justifying the traditional identification of the Nephilim as 'Giants'.
None of this explains how the Giants survived the flood, but we can see that they apparently did. If I had to hazard a guess, I would suggest the story behind Genesis 6.1-4 was meant to be an etiology for the presence of these Giants in Israel's folklore. They told stories of Moses slaying a Giant king, of David's elite warriors slaying Giants; where could such Giants come from, except by being descendants of a union of angels/gods with humans?
Genesis 6.1-4 tells a story of gods leaving heaven to marry human women and produce offspring. Their children (humans, as far as the Israelites were concerned) were a tribe of huge warriors, called 'Nephilim' or 'Giants'. Their warring led to the violence that brought the flood. Somehow, these Giants survived the flood, and became associated with a specific region of the land of Canaan. The Philistines eventually settled in this region, and apparently produced Giants of their own, including the infamous Goliath.