** Spoiler Alert ***
In Ridley Scott's Prometheus, which opened last Friday, a crew from Earth (circa 2089) is sent on a long journey to a nearby star system to explore a planet believed to be the home of the "Engineers," enigmatic creatures that supposedly engineered the human race.
Ridley Scott, it seems, is a believer.
“The more you go into it, the more you realize that it kind of makes sense,” Scott told FoxNews.com. “You stand outside at night, you look at the galaxy, and think, ‘The fact that we think we’re the only ones here is entirely ridiculous.’ It’s an arrogance to believe that we’re the only ones here.” http://www.foxnews.com/scitech/2012/06/04/lets-contact-aliens-sir-ridley-scott-says/
I agree with Scott that there is a reasonable chance life exists outside of the Earth. However, I think the probability that aliens had anything to do with the creation of life, or humans in particular, is vanishingly small.
It is with regard to human evolution that the science of Prometheus starts to go off the rails. The film depicts an anthropomorphic being sacrificing himself (itself?) to seed the Earth with his DNA. I have no problem with an advance race being responsible for injecting self-replicating molecules into the Earth's biosphere. However, it doesn't address the problem of ambiogenesis, it simply pushes the problem to the Engineers' home planet. Life had to originate somewhere; if not on Earth, then on the Engineers' world.
Where Prometheus completely fails is the idea that seeding the Earth with DNA almost four billion years ago would result in bipedal hominids that look almost exactly like the Engineers today (well, smaller and less grey). This highlights a fundamental misunderstanding about evolution: the idea that evolution has some direction or purpose.
Assuming that history played out in precisely the same way that it did, then bipedal hominids might have evolved after countless generations of prokaryotes, eukaryotes, anthropods, and other creatures that preceded us on the evolutionary ladder. However, the Engineers could not have predicted this.
There is no suggestion in the movie that the Engineers guided our evolution over time. However, if their goal was to create life forms like themselves, they could have simply engineered them and placed them on the Earth at any convenient time when conditions were right to support those life forms. Guided evolution would have required a degree of micromanagement and waste of energy that is inconceivable for anything other than the Christian God. Of course, this is precisely what some Christians, who believe in evolution, attribute to God. But unlike the Engineers, He supposedly has infinite resources and infinite time to carry out his purposes.
Prometheus isn't the first movie or television show to advance the idea of seeding DNA. Star Trek: The Next Generation had a similar premise and made the same mistake. Aliens seeded the Earth (and many other worlds) with DNA, which is an explanation for why most of the Star Trek races are bipedal hominids. The real reason, of course, was that the original Star Trek lacked CGI and the budget to make aliens that were more exotic than actors in costumes.