Pinning down exactly what Ridley Scott's larger-than-life Prometheus means may be impossible. But it's safe to say that the movie - the 3-D quasi-prequel to Scott's seminal technoscience-horror fable, Alien - is self-consciously a myth for our scientific era.

Prometheus opens over the shoulder of an alabaster figure on the edge of a prehistoric waterfall. This alien, called an Engineer, drinks a poison and falls into the waters. Our camera-eye follows, diving into his cells, which are darkening and cracking apart. Then we dive further - into his very DNA, which is rapidly rotting and unwinding, but not disappearing. We are left unsure where his broken-down DNA is headed. Cue title sequence.

Why does Scott open with an act of alien genesis triggered by crumbling, black DNA? Regardless of what else the filmmakers want the opening scene to convey, this is a horror movie. Its opening suggests that something about DNA and DNA manipulation is a source of dread - even as society today embraces biotechnology.

The biggest questions Prometheus asks may be, if DNA is a type of code or a language, who wrote the code of human life, and what did they intend for us? Our discomfort with the fact that manipulating DNA is a technique like any other - something you can learn and exploit for useful, perhaps lucrative ends - is driven by concerns over the motivations of those doing the manipulating.

If we were coded by authors with a motivation - the Engineers in Prometheus - can we be sure that we're acting on our own volition? Our discomfort with being "programmed" is logical, because free will presents us with a reason to behave more responsibly (you can't blame anyone else) and a gift of constant discovery.

The Engineers are not new to our trove of archetypes. In a way, they're unknowable like God, but in another way they're just a larger, paler version of ourselves. Scott makes this clear when his archeologists discover that we share genomes. Humans are the Engineers' golems, Pinocchios, and Frankenstein's creatures. The horror that comes with this discovery is that our makers are just about as ungodlike as we are.

The movie isn't really about the Engineers, however. The Engineers are us. Do we want life to be given purpose by people as fallible, silly, vain, and stupid as we are? Of course, we've been bioengineering already. Since the advent of agriculture and animal husbandry, we've shaped the genetic direction that species take. Think: wolves into Pomeranians. But breeding has always been a slow, sloppy form of programming.

So here we are at the gates to the age of biotechnology, where scientists bioengineer yeast and bacterial cells to produce materials for us like medicines and plastics, where they use genetically engineered viruses to manipulate the brain cells of mice as if neurons were the strings of a marionette. The moment when bioengineering becomes indistinguishable from computing is coming. Companies like Autodesk are already developing bioCAD software, and undergraduate students are doing bioengineering for their summer projects. With the Engineers - humanity's Gepetto - Prometheus offers a slant on where this all might lead.

Sure, just as the Engineers, we'll weave our own messy psychology into the life we make. But will we also leave something out? That is, free will - the ability to desire, act, and react in new ways. When behaviors are programmed, free will gets lost. Perhaps that's okay when we think about a lowly E. coli churning out fuel. But we feel disgust the more we can identify with the organism we're programming. Imagine owning a bioengineered dog that never veered from its hardwired instructions; it would be more of an appliance than a pet. And a completely programmed human being? This is the stuff of horror.

Science fiction's forecasts have many times hit dead-on (submarines, space travel, computer hacking). Stories that focus on biotech often come back to a central theme, perhaps the predominant question of our age: When DNA becomes just another toolset, what will separate us from any other object that's made? And what's transcendent about life if we can design it ourselves?

In the biotech era, the creation of new life may be the ultimate source of bio-angst-the feeling that there'll never be a satisfactory reason for our existence. If life is just stuff to be worked into new forms, then nothing separates life from ore, plastic, or anything else we can manipulate with tools.

Scott's Prometheus shows that - as a culture forced to make increasingly difficult decisions regarding science - we haven't escaped the debate central to Mary Shelley's Frankenstein or what she called The Modern Prometheus (no coincidence). Shelley's creature - abandoned by his genius creator - asks, why did you make me? Scott's movie just reverses the equation. In Prometheus, we are the creature, abandoned, and we want the Big Answer.

Prometheus is not simply the most recent, biggest-budget story of humanity's bio-angst - it's also the story that comes at a time when humanity is finally able to test the reasons for its angst empirically. Here at the opening of the biotech era, we're both excited and afraid of what our future holds.