Science knows for a fact that all the requirements necessary for intelligent life were present in the universe long before our earth even existed.  Life-giving elements were plentiful long before us.  Also, sun-like stars and earth-like planets are plentiful, and always have been since at least 11 billion years ago.  There are several reasons why earth cannot be the first planet to have spawned intelligent life.  The earth's young age, its location in the galaxy, its excessive uranium and iron content, and its evolutionary history. all these factors make earth a rather poor candidate for being the first planet to spawn intelligent life.  Astrobiology and evolution favor older, larger, less radioactive planets that are closer to the Galactic center.  So, intelligent life probably evolved before us.

 

Could aliens visit earth?  Deep space travel is quite possible using nuclear fusion and deuterium as fuel.  But why would they travel in deep space?  Survival of the fittest forces endangered species of intelligent life to keep expanding to new solar systems, to avoid extinction caused by ever-present genocide.  But why don't we see the aliens?  We don't see them because they don't want us to see them.  The aliens use planet earth as a source of genetic variety.  The aliens use earth's DNA for making new species among themselves, in a Breeding Program.  Apparently, they do this for their own evolution into various specialty species, not for the benefit of our evolution.  They want to keep this secret from us.  Also, aliens want humans to care about the environment, not because Mother Earth is sacred, but rather because extinctions decrease earth's DNA variety and thus inhibit the aliens' genetic engineering objectives.    

 

There is much scientific evidence from the fossil record that aliens have impacted evolution.  Many evolutionary events happened much too quickly for Darwin's theory of natural selection to be the only cause.  The most notable event was the Cambrian Explosion.  Shortly before the Cambrian Explosion, the most complex life on the planet were creatures that looked like UFO's.  Since then, extinctions have happened at regular intervals, for which the best explanation is extra-terrestrial causes.  There is also some indication that aliens impacted climate during late Ordovician and Silurian times, since certain climate changes of that time cannot be explained by naturalistic forces.  There are even cave paintings that seem to depict aliens.  Today, there are many reports that extinct species have come back to life.  Some of these come from cryptozoology, like the Loch Ness Monster and the Beast of Gevaudan; however, other reports come from respected scientific journals.  One famous example is the coelacanth fish, which is known from science.  Do the aliens keep extinct DNA on ice?  Are they operating a secret Jurassic Park in the mother ship? 

 

Would aliens invade earth to take it from us?  No, because living off the land is primitive.  They don't need our resources.  Besides, an easier way to get rid of us is to pollute our gene pool so that we evolve back into apes.  There is fossil evidence that primitive hominids existed at times long after their supposed extinction.  The legend of Bigfoot makes some people laugh, but there are other primitive fossil hominids of a late date, which are taken much more seriously by mainstream science.

Read more about the evidence for why intelligent life most likely evolved before us and most likely has visited us.

The creationist narrative in Genesis 1 is contradicted by many ancient Christian texts.  Instead of an Almighty Creator God, ancient Christian texts espouse that the universe is born from blind arrogance and stupidity.  The angels caused evolution to occur from species to species.  There are many gods, (or aliens?), and the Christian God is just one among them.  Satan the Devil writes scripture, and thus the Bible was polluted with Genesis 1.  Archaeology and modern scholarship demonstrate that Genesis is indeed corrupted.  Cavemen walk with Adam and Eve.  Esoteric prophecies reveal the coming of Christ, and also reveal the dark forces that govern the cosmos.  Such are the ancient Christian writings.

Science vindicates the truth of these ideas.  Evolution often happens too fast for Darwin's theory.  Gaps in the fossil record indicate that some kind of unnatural force acts together with natural selection.  Astrobiology reveals that intelligent life probably evolved long before us.  The fossil record reveals strange clues that aliens abducted species and transported them across oceans, and that DNA from diverse lineages was combined to spawn hybrid species.  Evidently, aliens influence evolution, and they are the gods of the world's religions. 

This is not fiction.  All these facts are thoroughly documented in the links above.