It is ridiculously implausible to think so. And the absurdity was recognized more than a decade ago by Francis Crick, co-discoverer of the DNA double helix. Yet Crick is a committed atheist. Unwilling to consider the possibility of divine or supernatural creation, Crick suggested that maybe aliens brought life to earth from another planet. And this is precisely the suggestion that Richard Dawkins makes in his response to Ben Stein. Perhaps, he notes, life was delivered to our planet by highly-evolved aliens. Let's call this the "ET" explanation.
Stein brilliantly responds that he had no idea Richard Dawkins believes in intelligent design! And indeed Dawkins does seem to be saying that alien intelligence is responsible for life arriving on earth. What are we to make of this? Basically Dawkins is surrendering on the claim that evolution can account for the origins of life. It can't. The issue now is simply whether a natural intelligence (ET) or a supernatural intelligence (God) created life. Dawkins can't bear the supernatural explanation and so he opts for ET. But doesn't it take as much, or more, faith to believe in extraterrestrial biology majors depositing life on earth than it does to believe in a transcendent creator?