=================[mild spoilers follow]=========================
=================[major spoilers below]=========================
Going back to the unexplained, lets look at the main thesis of the film. The opening scene of Prometheus seems to show the creation of life on a lifeless planet (presumably earth) when one of the "Engineers" (so named because alien is used for the creatures) distributes his DNA into the water cycle. The idea that either life itself or its molecular building blocks came to earth from somewhere else, and that this event jump started evolution, has been around at least a few centuries under the name panspermia, or more recently, exogenesis. It hung around even within scientific circles because to this day science has nothing that even comes close to a viable theory for the origin of life. I always found that amusing since the space seed theory doesn't explain life's origin either - it just places it somewhere else where it may have been met with better conditions... uh, right. Let's move on.
But the film doesn't even try to be scientific on this matter. First, there is clearly vegetation on the planet already when the Engineer arrives. If they did some terraforming in advance, then where did the DNA for the plants come from? It is made of the same molecules as animal life. Let us then assume that the deposited DNA is the seed that begins animal evolution. We find out later that the Engineer's DNA matches up almost perfectly with ours. If the evolution of life is based on random mutations (as believed today), then the chances the end product would match the DNA seed material is absolutely zero. If instead we are to believe the Engineers continually visited Earth to guide the process, then why would they need to seed it with their own DNA to begin with? How about this... the Engineer at the beginning looks exactly like the ones seen in 2089, but if the planet in the opening is earth, they would have been separated by roughly a billion years. Wouldn't the Engineers' race have evolved in that time too? If the opening represented a more recent event on another planet as an illustration, you have the same problem in reverse. They were doing the same exact thing a billion years ago? What an inconsistent mess!
There are lots of unexplained things that can be chalked up to the weirdness of alien fiction, like why the mother ship in the opening is different from the one at the end, the meaning of the mural on the ceiling of the armory chamber, or that big stone head bust which they use on all the movie posters. It may look cool, but it's just a random item in the film. On the other hand, there are also lots of unexplained things that look like oversights or just poor story telling. I've listed below some that struck me as I left the theater:
- Ms. Vickers has a state of the art living quarters complete with a robotic medical chamber that performs automatic surgical procedures. We find out later at a critical point in the plot that it is only configured to operate on males. Why was it installed in her quarters again? Ok, we also find out it was meant for Weyland - but for him only? Did his own daughter approve this decision?
- David reports that he has been studying the origins of human language to its common roots and thus believes somehow that he can communicate with the Engineers. When the opportunity comes to do so, the Engineer responds to his query by going on a rampage. No communication ever takes place, an element that might have added some interest to the story. Instead, we don't even know what question was asked.
- One of my few complaints about the original Alien is how the creature grew so fast without consuming food. At least that was off screen and took a few days. In one scene in this film, the creature in the operating chamber grows rapidly before our eyes in a matter of seconds. That's just not biologically possible even for an alien.
- If the planet they landed on was not the Engineers' home planet, but instead a laboratory for military experimentation, why would its location show up on ancient cave paintings around the world? The Engineers did not seem to have any good reason to reveal such information to their experimental subjects.
- If David's goal was to capture the alien offspring in cryogenic stasis, why didn't he just keep Dr. Shaw sedated? Instead he lets her awaken and tells her she's pregnant? He seemed so much more cunning in other scenes.
- I was reminded of this one on another review site - David finds some green goo on the wall when they first enter the caves. That usually means some dangerous creature is lurking around. It is never explained and never appears again, and it turns out there is nothing living in the cave system when they first arrive.
- Before David effectively poisons Holloway, he asks him "How far would you be willing to go to find your answer?". When Holloway answers that he would do anything, this supposedly gives David a justification for his action. Since David is a robot, why does he need justification? He does not seek justification for other unethical actions in the film. But even if he was programmed to seek it, Holloway's answer does not logically provide it! The answer assumes willing participation. David gave Holloway no choice in the matter. A human might make such an erroneous transfer, but not a robot driven by logic.
One of the more interesting characters in the film was the android David. As I witnessed the completely unethical methods he used to achieve his master's goals, including outright deception, it reminded me of the rationale behind Asimov's laws of robotics. David certainly broke the first law by performing a fatal experiment on Holloway. In a world where robots have no constraints on their behavior, wouldn't it be impossible for humans to trust them?
The final oddity I have to mention is that for a prequel, there really isn't much connection to the actual events in Alien. Even though the Engineer's ship crashes in the end, we know it is not the ship found by the Nostromo because, among other things, the pilot leaves his cockpit. Indeed, I have read that the planet they visit is not even the same one as in the original. It almost seems like a smooth connection had been thought out but the script was changed at the last minute. In fact, most of my complaints are with the script, and I hear the re-work was done by Damon Lindelof, one of the writers for the Lost TV series. I would conclude he is probably the wrong person to be writing science fiction. Look at all the unexplained stuff he left over at the end of Lost, and it got those fans upset about it too. I wouldn't be paying it much attention if this film had not represented such a historic opportunity, one that I'm sure will not come around again.