- The Nefelim were the races of giants that existed in the old world, before the Flood.
- In the end of Berashis it says “The Nefelim were upon the earth, and also afterwards”.
- “Also afterwards “ is referring to after the flood.
- Og was the only member of the races to survive, his traits were passed to his offspring. Since Og was not as strong as the original Nefelim some of the genes would have become passive. Yet, we see he was able to produce the Refaim and Giants such as Arbah and his three sons.
- However we find that Noach’s wife was Namah, sister of Tuval Kayin, a descendent of Kayin whose family had strongly interbred with the Nefelim.
- Even though it was in the blood from both sides it was not condensed enough, all the giants leaving after the flood were of a much weaker nature. There were also great changes in the atmosphere, which help cause this.

(Minchas Yehudah , Berashis)