The book of Enoch clearly explains the Watchers, the Nephilim and Azazel, the angel who taught the secrets of divine knowledge to man. This cannot be ruled out because the book of Genesis clearly states that the "sons of God" took daughters of men, and giants were born unto them.
Where did men learn the arts of warfare, witchcraft, deception, roots, metals and so on? Clearly the Egyptians knew, for written in their hieroglyphics were winged creatures who walked among them. These winged creatures were the Fallen Watchers of Enoch and the parents of the Nephilim in Genesis!!