Hadriel - To suggest an intelligence is behind the diversity of life we see on Earth is, scientifically, exactly the same as saying God is behind it. Both avenues offer nothing in way of an explanation because you could say "intelligence" or "God" for everything we see here on Earth and we have no way of falsifying that claim. That is why Intelligent design, or God did it, is not scientific.
To clarify, it matters not whether your intelligence is an alien or a god as both suggestions offer nothing for us to learn.
However, if an Alien species were to land, or we were to find something on a nearby planet/moon, and we could analyse what makes them work then we would have some evidence with which to build a hypothesis that could then be tested. Up until that point the only life we have to study is what is here on Earth...
As an aside there are scientists studying organic compounds found in space (profusely actually) and the scientific findings of those researchers may allow us to widen the net used to consider the beginnings of life on Earth.