You have chosen a subject akin to squaring the circle :)
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The Biblical flood is well documented.But two enormous cataclysm's took place on earth in more recent times. One of these events terminated the Middle Kingdom of Egypt and another catastrophe in the seventh century BC devastated every populated place in the entire Near/Middle East.
Fossil beds in Europe,American,Asia and other places,bear silent witness to the same destructive processes.The last around 687 BC.
"Great multitudes of animals that filled the plains and forests,water and air,were more than 'once' suddenly called upon to write their names in the register of extinction."
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The 'veracity' of the bible has been under fire since vast numbers of texts discovered in Nineveh around the 1860s were translated by scholars. [Sitchin]
Brief summary..
We are of but the Stars.This statement was not the mental wanderings of an ancient poet,for he and others of his time related to the probable origins of mankind.
Mesopotamian texts describe the appearance,activities,mode of travel and intent of these beings.The Anunnaki/Neflim arrived on Earth 450,000 years ago from a planet called Nibiru.
These records show that over the next 150,000 years,they established functional bases in many areas.Sumer was the first city of men.
Their main activity initially,seems to have been mining for specific ores in Southern Africa.The metals were sent aloft to orbiters then transferred to spaceships periodically arriving from Nibiru.
Great power battles took place during these times brought about by two brothers wanting to control Earth. Enki,the supreme commander of the Anunnaki,was the persecutor of mankind.The other,a chief scientist called Enki,was man's greatest asset.
They settled their differences [temporarily] so that work on establishing a solid base on Earth could continue.
During this armistice the rank and file members of the Neflim [records show there were initially 600 of them] had a mutiny. Their work was too hard.
The trigger was that they knew experiments were taking place regarding a primitive worker to assist them and to eventually take over their toil in the Abzu.[Zimbabwe]
So faced with an urgent need for manpower,the Neflim resolved to create 'slaves' in vast numbers.
Neanderthal was chosen for the experiments.He had a large brain and was far too wild to become a docile beast of burden.His physique had to be modified.He had to be able to grasp and use the tools of the Anunnaki and bend like them.
He had to have "better brains",not those of the Neflim, but enough to understand speech,commands and the tasks allotted to him.
First experiments to create hybrid workers was not a happy event..One text tells of a man with two heads and wings, some had limbs of a horse behind and in front were fashioned like men.Others had the head of a goat.
These details hold an important truth.The Anunnaki, were using animal sperm for their first experiments.All part of trial and error process.Eventually,using their own genetic code,the long awaited perfected man came forth.
They called him Adapa, [biblical Adam] meaning earthling. The Neflim were now genetically compatible with...enter Cro-magnon.
This re-constructed wild man could now procreate,producing quality workers.As time passed Cro-magnon's daughters held more than a passing interest for the Neflim,who gradually took for themselves wives and lovers in great numbers.
Many other strains of hybrid man were produced over time. Modern man is the handiwork of the Neflim.Without their intervention we would still be light years away from our present form.
Life from that point,in our interrupted evolution,severed us from our roots.Man's lingering belief of a golden age in his pre-history,probably stems from his genetic memory that links him with Neanderthal.
Our Numbers kept increasing until the time of Noah's flood, which was foreseeable by the Neflim.By this time they'd witnessed a marked decline in their genetic makeup,brought about by interbreeding with hybrid man.
The Anunnaki wanted the flood to take all humanity,so that they could maintain their superior genetics.
Chief scientist Enki had a favorite son in the hominoid ranks.Originally known as Atra-hasis/Utanupistim.[Noah]
Enki secretly warned Noah to build a submersible craft.
The Sumerian texts relate that the coming flood,as seen through the eyes of the Neflim,was a necessary universal cleanser.Their own safety was assured,for as the flood approached,"they lifted up their rocket ships like torches and set the land ablaze with their glare."
Circling the Earth,they were aghast at the level of chaos and destruction.Initially thinking that the Earth would be uninhabitable forever.
The upheavals that drove the Anunnaki from Nibru was still in their memory.Now the vast destruction here on Earth- what were they to do?
All the cities,manpower and facilities were gone,with one exception,Noah and his crew.Neflim needed man like never before.The final outcome of all the previous transgressions namely the watering down of their seed ,came to a workable solution.
They were simple. Man sleeps with his own kind and still does the hard toil.The Anunnaki wasted no time.Rolling up their sleeves they applied advanced knowledge for the growing of "super crops."
Their own survival depended upon the speed with which all this could be done.
Spectacular events happened during the next hundred years. Many of the ancient grains became high yielding and uniform with exceptional nutritional value.
Left in the hand of nature,this process takes thousands of years of genetic selection to obtain a moderate degree of sophistication.
One grain in particular--spelt--stands out for analysis. It is the product of an unusual pairing of botanical genes that doesn't "just happen" via nature.This grain has been genetically engineered,just as many of our food products are today.
Science today is rediscovering that which was known to the ancients.
The Sumarians knew the answers regarding the spectacular richness and variety of the produce that came forth,even before the flood waters had receded from the hills to the plains below.
"The wheat,barley,fruits and hemp were lowered to Earth from the Twelfth Planet.[Nibiru]
Then around 3700 BC mankind's numbers had expanded rapidly, once again ,threatening the Neflim. So they decided they needed an intermediary between themselves and the masses.
They introduced Kingship on Earth,appointing a human ruler who would assure mankind's service to the Anunnaki and pass on the teachings [indoctrination]and laws to the people.
By 3400BC,the population had totally rebuilt all the cities temples,space-stations as they were before the flood and had constructed the first royal city of men.
By this time the Neflim were declining in numbers and they feared a human race unified in culture and purpose.
So they introduced the four regions.Taught man different languages and dispersed him via three of these regions,. The fourth region they kept for themselves,Tilmun [Sinai] which means place of missiles.Other space related sites were Baalbek and Jerusalem.
The final insult to mankind was the classic policy-divide and rule.Give them a belief system,then they will spend most of their lives fighting and arguing and killing themselves defending their belief.
Of course,man now had a language barrier to contend with as well.
All this confusion and chaos enabled the Anunnaki to get on with the real work of running and controlling Earth, while the majority of mankind ran around with this new found mental and emotional chaos.
Since that time the Neflim's way of dealing with man has been subversive in appearance and intent.The free willed experiment was to be left alone? Not likely!