In a lecture at New York University in 1993, Sitchin further outlined his theory about human origins and our link with the Anunnaki by saying, “Ancient history and legend around the world, as well as the Bible, attest to the fact that there were once giants in the earth; men of awesome dimensions, bulk and height. In Genesis 6:1-4 we read,
"And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them, that the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose...
There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, that they bare children to them, the same became mighty men which were of old, men of renown".
The Book of Enoch, an ancient text discovered in Ethiopia in 1773 (and because of references to it in ancient Hebrew writings considered to be among the oldest manuscripts in existence) speaks about 200 angels who came down to earth to mate with the "daughters of man".
Led by a high angel named Azazyel, the angels produced giant men. During this strange occupation, Enoch writes that humans were taught to make swords, knives, shields, breastplates, mirrors, jewelry, paints and dyes, make cosmetics, and use valuable stones.
The people also learned sorcery, use of roots and plants for medicine, astronomy, astrology and other "signs", and the importance of the motion of the celestial bodies