The first episode of the "Ancient Aliens" cable-TV series promised to show that the growth of intelligent life on this planet had help that came from the stars.

The Prometheus Entertainment summary in 2010 asked: "If ancient aliens visited Earth, what was their legacy, and did they leave behind clues" that still exist?

The bigger question, nearly 200 episodes later, is whether aliens provided the building blocks of life itself. That's the kind of subject -- both theological and scientific -- that surfaces whenever there are debates about whether extraterrestrial life exists.

It's one thing for a recent U.S. national intelligence report -- "Preliminary Assessment: Unidentified Aerial Phenomena"-- to discuss incomplete technical data and the possibility of hostile spy drones. It was something else to say that experts had no scientific explanations for 140-plus reported "UAP" episodes.

The summary noted that 18 mysterious objects "appeared to remain stationary in winds aloft, move against the wind, maneuver abruptly or move at considerable speed, without discernable means of propulsion."

This raised familiar questions for those who have followed decades, even centuries, of debates about these mysteries: Who created these objects? Who created the beings who created them? Should this planet's religious leaders worry?

"The logic is that many people assume life is special, that human beings are uniquely purposed and created in God's image and that this life -- life made in God's image -- cannot exist anywhere else," said Stephen C. Meyer, who has a doctorate in the philosophy of science from Cambridge University. He is known for writing controversial books, such as "Signature in the Cell: DNA and the Evidence for Intelligent Design" and the new "Return of the God Hypothesis."

Many experts seem to think Christianity has explicit doctrines on this matter, he added, but "that's not a sound judgement, since there's no explicit Christian teaching on the subject -- unless we have now taken C.S. Lewis as canonical."