The Book of Enoch tells a tale of an alien race of Reptilians, known as the Dracons from the Draco Constellation, that interbred with early human females, Homo Erectus, an extinct species of man which evolved before us, some 40,000 years ago, to produce the Nephilim.
The Nephilim were giants with fair hair and pale skin and large elongated eyes, as babies they were huge, often needing to be delivered by cesarean section. The process of interbreeding is still being continued to this day long after the Dracons left and returned to their home planet, which is just a guess at what happened to them. This concoction of alien and Homo Erectus, ancient humans, before what humans are today, the Homo Sapien, us, meaning intelligent. A slave race to work the Dracon's gold mines here on earth.
One off-spring was a man we call, Noah, a Nephilim, a Reptilian Hybrid, of Genesis flood fame. The Book of Enoch called them Anunnaki which means crossbreeds, and are also mentioned in the Dead Sea Scrolls as descendants from Watchers, the Anunnaki and Nephilim.
We all have depictions of what Noah looked like. A white, pale skinned man, with long white blondish hair, with eyes that made the "whole house shine." He is said to be the son of Lamech, a supposed God, unlike any other human.
He had special knowledge of the on-coming disaster, being warned by his fellow aliens to prepare himself, which actually makes sense that a Nephilim would be warned on how to continue the human race. To preserve the seed of mankind. Why would they notify a human, and not one of their own?
One of Noah's sons, Cain is mentioned in the Kebra Nagast, a thousand year old script, which describes his daughter unable to bring forth live babies, because they were to big, produced from the sexual encounters with the Gods (Dracons).
This also explains why Noah is so important with most religions. The book of Enoch was banned by the early Romans, they were too afraid of the truth at the time and didn't want their flocks to know the truth. The truth being, there really were flesh and blood angels called Nephilim that descended from the skies, and interbreed with humans.
Many people today believe themselves to be direct descendants of Noah and the Nephilim.
Reference and Recommended Reading: The David Icke Guide to the Global Conspiracy