It is supposed by some that aliens may have once deposited some biological material on our planet which has now evolved into all the different species we have today. This theory allows us to hold on to Evolution, as well as providing an explanation for the origin of life itself on this planet. But I suppose that if aliens brought life to this planet, they might just as easily have brought with them every species that is alive today, already “fully evolved”, in a sort of inter-stellar Noah's Ark. People like the first version of the theory because they see evidence of evolution taking place on this planet. But let's imagine that aliens did bring along every species, fully developed as it is today. We might wonder about the origin of these species. Maybe they evolved on some far distant planet in the same way that we typically assume life on this planet began? But we thus remove any possibility of investigating it scientifically. It might be just as likely that this alien race genetically engineered all of these different species themselves; including mankind. According to this theory, we basically have a creator-god in the form of an alien race. Well, you can speculate anything, but I’m interested in theories based on what we know about the “Roswell aliens”. Could they have seeded life on the Earth? Some people think so, and have suggested that the God of the Bible is really one and the same as these aliens which are supposedly flying around the Earth, abducting people and crashing into Roswell. All of the miracles – the flooding of the whole Earth, the parting of the Red Sea, and all the other miraculous activity of the Bible is really the activity of aliens. After all, what we know about them suggests they are capable of what appears to be super-natural. People have observed UFO's which can change direction without slowing down, and aliens which can travel through walls. And of course, if we wanted to maintain that aliens are the “true God”, Jesus Christ would clearly be half-human, half-alien, to explain his ability to perform the miracles he did. So some people believe.
If you don't believe in God, but you do believe that aliens brought life to the planet Earth, you may have for yourself an explanation of life on Earth. But you don't have an explanation for the origin of life itself, because we are left to answer the question “What is the origin of the alien life?” Since they do not appear to be subject to the same laws as our universe, we must assume that they are from another dimension. In our universe, everything has a cause; what happens at this instance of time is preceded by some event prior to it in time. And so we have the process of evolution requiring time... lots and lots of time. Evolution is a long chain of causation; event after event leading to the diversity of biology we see today. But these aliens may be from another dimension where time is not a necessary factor. Or maybe, in their dimension, it makes sense for something to just come into being out of nothing? Believing in the aliens as the origin of life could solve a lot of problems for evolutionists.
The problem with naturalism is that it rejects anything which cannot be perceived by our senses, as though all that truly exists is what we can potentially see, or hear, or touch, (etc). Thankfully, many people see the fault in this, and so this idea of trans-dimensional aliens is acceptable for them. Yet this same explanation for life on Earth could be applied to the Creator-God of the Bible, since God Himself exists in some other dimension, (it would seem, since He can see all of our time and space instantaneously). It's not so crazy to believe that something outside of the dimension of time and space could have “always” existed. (Though in fact, the concept of “always” doesn't even make sense outside of time.)
Now, people might believe that aliens, being from another dimension, need no explanation for their origin, but do explain the origin of life on Earth (that is, they brought it here.) But at the end of the day, nothing about the aliens’ origin can be proven because their universe is beyond our investigation. The only way we could ever know that aliens from another dimension brought life here is if they came here and revealed this information to us. This leaves us with the revelation of the Bible, which tells us of a loving Creator-God, versus the mere possibility that life was brought here by what turns out to be quite malevolent beings who are, themselves, subject to death (if we believe that aliens died at Roswell). Well we can't just decide which option we'd prefer to believe in. We need to decide what is true, and believe in that. As I read my Bible, the narrative does not show itself to be man's interpretation of alien activity since, for example, it maintains that Yahweh is one God (in three persons; no more, no less). And it doesn't sound like a story given to man by aliens, either, since their description of God (which would actually be of themselves) is entirely false, and the lie would serve no purpose. On the other hand, we know that Devil and the fallen angels are malevolent, and are bent on deceiving and corrupting mankind, and that they exist in a dimension outside of time and space... the more reasonable explanation is, in fact, the Christian view; that aliens are demons, and that life began by the Word of God.
But even if we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed. (Galatians 1:8)