The acting was decent, the sets and costumes were stunning, and the special effects were breath-taking. But the plot? A disaster!
It opens with a monkish-looking alien standing on a cliff above a lifeless, but watery world. He takes out a container of some dark, metallic, weirdly mobile substance and consumes it in a solemn ritual, whereupon he - literally - falls apart, and his flesh and bones merge with the primordial waters. The only thing I could think of was "Don't take the Brown Acid, dude!" Somehow, several hundreds of millions of years later, his DNA winds up in Homo Sap. That is not how DNA works. That's not Science Fiction. It's Intelligent Design run amok.
Which also makes me wonder: if our DNA is identical to the Maker, then why aren't we all nine-foot-tall hairless albinos with no whites in our eyes and Industrial/Goth/Deco bones and muscles? I know there's a huge variation in human height and pigmentation, but our skeletons are arranged in much the same manner everywhere. We don't have strange bony structures in our limbs.
I'm thinking that some giant black slab that somehow mutated our neurons (microwaves?), turned us into murderous tool-makers, and split us off from the chimps is sounding a lot more plausible.
That was only the beginning of holes in the plot that any Sophomore science major could have maneuvered a double-wide through. How does someone who's only days away from dying survive cryo-sleep, when even the young and hale are violently ill and debilitated upon awakening? And why the hell would anybody build a spaceship completely embedded in a solid stone structure? What did the Alien Thing eat in the isolated medical pod to grow to the size it did? You can't create that kind of mass out of random scalpels and IV fluids!
And the scientist who presents himself as a skeptic has a crucifix tattooed on his bicep. That's not a science error, but it's a grating incongruity.
It's a pity that considering the talent and effort that went into this film that they didn't hire a real Science Fiction writer. Those guys and gals are no dummies. They could have gotten it right.