David Duchovny and Julianne Moore

David Duchovny (The X-Files), Julianne Moore (Hannibal, Boogie Nights) and Orlando Jones (Bedazzled) manage to keep things light while shouldering the heavy responsibility of being the only things standing between the aliens and their free lunch, courtesy of the human race. Warning, the jokes, mostly crude sexual innuendoes of the American Pie flavor, peek out at a Junior High School level of sophistication. But before the movie mudslides into the abyss of Adam Sandler territory, an actual story kicks into gear, accompanied by enough high-tech tension to keep you on the edge of your seat until it's time to relax on the next of Reitman's rapid-fire whoopie cushions. Also on hand to keep Evolution moving is veteran Ghostbuster Dan Aykroyd, as Arizona Governor Lewis, a guy determined to defeat the aliens even if it means napalming his own state.

Evolution's ensemble cast performs admirably. Even college biologist Ira Kane (a typically deadpan Duchovny) and his rival U.S. government epidemiologist, Alison (a curvaceous and clumsy Julianne Moore) manage a beaker's worth of kooky romantic chemistry.

Hats off to the special-effects team at Tippett Studio for creating creepy, crawly creatures, each as vicious and viscous as the next. They're as much the stars of Evolution as any human on the set. This is not surprising, given that special-effects supervisor Phil Tippett's résumé includes work on both the dinosaurs of Jurassic Park and the huge alien bugs that infested Starship Troopers. If you're the least bit squeamish about things with eighteen legs and razor-sharp incisors, Evolution may not be the movie of the week for you. Then again, a seat front and center may cure your phobia once and for all. Just a theory.

As long as we're talking hair-brained hypotheses, Evolution's producers claim the scientific theories at the crux of the story are held as fact by a small number of somewhat mad scientists. Panspermia, the idea that life travels from one planetary system to another by way of meteors that crash into a previously lifeless planet, is an intriguing premise and who's to say that life didn't start that way here on our little planet Hollywood. Of course, most "sane" members of the lab-coat community believe that life somehow evolved from bubbling primordial ooze, similar to the goo inside lava lamps. Not to discount divine creation, but for a religious movie like that, Reitman would have required Charlton Heston, an actor not known for his comedic talents, at least not intentionally.

So, if sci-fi comedy like Mars Attacks, Galaxy Quest or Earth Girls Are Easy is your cup of interplanetary tea, then you're bound to buy into this summer's theory of Evolution. It ain't rocket science, but who wants to go to summer school anyway.