For almost a decade, director Ivan Reitman has been talking about making a second sequel to his 1984 blockbuster comedy Ghostbusters.

With Evolution, opening in theatres today, Reitman has finally realized his dream.

Instead of weird, shape-changing poltergeists, it's weird shape-changing alien lifeforms that threaten to wreak havoc on mankind. Different creatures and different heroes, but basically the same story and the same shtick.

A meteor containing an alien life form crashes to Earth near a desert community in Arizona and an extraterrestrial lifeform begins evolving at an astronomical rate, threatening to take over the planet.

The fate of mankind lies in the hands of a small team of self-styled alien-busters.

Ira Kane (David Duchovny) and Harry Block (Orlando Jones), a pair of teachers at the community college, team up with a country club pool boy named Wayne (Seann William Scott) and Allison (Julianne Moore), a top epidemiologist from the U.S. Centres for Disease Control and Prevention.

An unlikely quartet if ever there was one, which ensures a winning balance of slapstick and subtle humour.

Allison is as klutzy as she is brainy.

Harry is a fast-talking, lecherous opportunist while Wayne is all wide-eyed disbelief.

Kane holds a grudge against his former employer, the U.S. armed forces, and carries a secret torch for Allison.

The interplay among the characters is as crucial to the fun in Evolution as the aliens themselves.

That's some achievement considering just how eye-popping and believable visual-effects creator Phil Tippett's lifeforms seem, especially his dinosaurs and apes.

Most of the early lifeforms are played for gross-out humour, but as they climb the evolutionary ladder they become more realistic and identifiable.

As with Ghostbusters, Reitman has great fun with nauseating goop that oozes from the largest and most shapeless of lifeforms. And before the end of the film, the entire cast gets slimed.

Reitman also keeps the level of humour as basic as possible by having the creatures pass wind, invade the private parts of humans and use the more obnoxious humans for fodder.

Jones and Scott are given full rein to mug shamelessly while Moore and Duchovny get their laughs by sliding in as many witty, barbed remarks and retorts as possible.

Dan Aykroyd plays yet another bombastic authoritarian figure and Ted Levine is the obligatory raving military egotist.

Evolution is amusing, but it's not as wildly extravagant as Men in Black or as devilishly clever as Galaxy Quest.

It doesn't take nearly enough comic jabs at such classic sci-fi invasion flicks as War of the Worlds, Invaders from Mars and The Quartermass Experiment which are the dramatic equivalents of Evolution.

It also shows that Reitman's filmmaking hasn't evolved all that much in the past two decades.

He's just getting better at recycling. (More on: Evolution)

(This film is rated )

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