I have come to believe alien greys were actually terrestrial people before our time, who evolved into a highly intelligent people and had to share this realm with us for a period of time when they were prepared to go to the next level of knowledge that takes us out of this limited world we still inhabit.
They were not strong, perhaps, but so intelligent they might have found a way to bypass this realm to enter a completely different parallel world in which they still sift to and from and visit us upon occasion to see what us brutes are up to.
Relics of such beings were found in Africa and referred to as Boskop Man.
They were believed to have an average IQ of 150. When we Homo sapiens get people in the 170s IQ, we manage to get some good inventions, concepts, and changes in our world, but imagine if all our people had that kind of head room?
Why did they not survive here?
Well, competing with another rising human form that was powerful physically might have been more than they wished to endure and so they pushed themselves to find a way to use their natural understanding of the world in ways us primitives couldn't conceive. Imagine the comparison of a man lighting a cigarette in front of cave men? What kind of magic and alchemy is this???
In fact, today we might be nearing a place where we will figure out how to pass through that realm into their world. This would not be advantageous to their agenda of staying alive and perhaps seeking peace, so they may need to work with our people in terms of "abduction" and "contacts."
This could all be an agenda to either promote our focus (creativity versus technology) or our intelligence and fertility. What if you wanted to keep a race of humans from focusing on technology that might move them to your realm or even harm your realm? How about you introduce genetic issues with breeding or breeding intelligence? Simply keep them primitives of a sort?
We may look at this concept in this way: The Earth was a kind of gladiator coliseum. Types of man developed here, competed for who would be the ultimate winner for this planet and here we are today.
But where are they now?