Long post alert! I am not highly educated, no PhD, I didn't go to Uni but here goes. My theory is much simpler. Ever since Man opened his eyes and looked up at the sky he has wondered how it gets light, how it get's dark, what all those lights are, how did we get here and how everything works. As intelligent as we think we are we still do not know anything and all we have is theory. Theory is just an idea that you convince enough people to believe then it takes flight and becomes accepted fact, EG religion. A God of somekind, some great all powerful thing always unseen, usually living in the sky must have made us, now it could be in 6 days with a Sunday off to put his feet up or it could be some visitor with a head like a bird of prey. That's one theory, that one has been forced upon people by violence for hundreds of years. Conquerring is the main way religion is spread. Usually as a means to rape a country of it's wealth and control the population. Once it has a foothold successive generations forget the violence that was used to put it there and it becomes faith, faith is the belief in God. That's it, belief without substance or proof of any kind we just believe the words in a book written convienientely a long, long time ago because our ancestors did. Now if that is your thing and you live a peaceful and blessed life fantastic. I wish you and your God all the best wishes. Virtually all religion is peaceful and does no harm to others, it is a great way to live your life. Thou shalt not do anything but good isn't a bad idea is it?
Then we have another theory, again just an idea that people subscribe to and belive, every bit as real as religion to them that have faith, that is Evolution. The fact that everything evolved millions of years before we were here again makes it easy to spread, this theory isn't forced on people and is usally held by the people who poo poo the idea of God's because they think they are more intelligent or scientific than those people. How can an unseen entity create a planet with the wonder this has.
They believe in a meteorite crashing, an Ice age, a Global warming, in fact anything but a God, but again it is un proven.
Anyone who says there isn't a God but a Yorkshire Terrier is decended from a Wolf needs to have the same conversation with himself that they believe someone who believes in God has to have.
Everything has evolved and nothing has changed in the time we have been running around destroying this wonderful planet. an Elephant still gives birth to an Elephant, a Lion has another Lion, not a Cheetah. If they lose their food source they don't suddenly become vegetarian and start eating grass. They die out. If they did suddenly start eating grass this is called evolution. It doesn't happen now, it happened before us.
I rather like the alien angle. We once had wonderful structures, Pyramides and Temples, Marvels of the earth when we didn't have the brains to build such structures. Hence why to this day no one on planet Earth can explain how a Pyramid was constructed. Things like that don't get forgotten, someone passes it down through words or text. We cannot explain Stonehenge properly. How can people who had no transport get those stones there and raise them to those heights with no tools whatsoever. Hardly likely is it. But yet again someone comes along with a theory and once again if enough people can be conned into believing it it becomes fact. We think they did it this way. They then try it and it always fails, miserably
In the end we had to have got here somehow, we had to have been brought here by someone. Personally I see Earth as an Aliens Zoo, a collection of things from everywhere brought and dumped for their amusment. I believe there is more truth in the Predator films than in a religious text. Apologies if that offends Christians, muslims, jews, buddists, hindus etc or indeed Darwinians, Anyone else want to join in my theory? It might just become fact if I can get enough interested.
