If "The Croods" is an example of what's supposed to be prehistoric comedy, then the genre should be allowed to become extinct. There's the potential for humor, but it never develops beyond a few sight gags that will entertain the pre-school crowd.

The movie follows a family of cave dwellers - The Croods - who only venture out long enough to search for food. They are afraid of anything new, the dark and, apparently, any joke that doesn't have to do with one of them falling down. The only member of their group with an adventurous heart is Eep (voiced by Emma Stone), but she would have to defy her protective father, Grug (Nicholas Cage), if she wants to see the world.

Eep and the rest of the family are forced to face life outside the cave when they are informed by a passing stranger, Guy (Ryan Reynolds), that the world they know is about to change and they must head to higher ground.

This is where "The Croods" turns into a one-trick tale. The group fumbles and stumbles through a series of physical gags as they travel through dangerous forests, prickling fields and deep waters. After you've seen them fall, flop and flail through one or two landscapes, the rest becomes dull redundancy.

Unevenness and inconsistencies are the norm. There are times it looks like screenwriters and directors Kirk De Micco and Chris Sanders are trying to make a story set in our distant, distant, distant past. But the film moves through so many alien environments and features so many weird creatures, it could take place on the sister planet to where the "Avatar" gang lives.

There could have been great humor in watching the Croods claw their way into the civilized world. The addition of Guy - who plays more like a time traveler from the future than a prehistoric smarty - takes away from the Croods discovering fire or swimming on their own.

"The Croods" falls somewhere between being a story of an uncivilized cave family and "The Flintstones." It's not a good place.

Even the animation is all over the drawing board. Grug has the traditional caveman look, but Eep's form-fitting tiger skin seems more suited for a Miss Pre-Civilized World Pageant. Guy could have been plopped down in any animated film and not looked out of place, but Gran (Cloris Leachman) looks more like a cave wall drawing with her distorted features.

"The Croods" would have worked if the humor and animation - the 3-D effect is minimal - had been more evolved.

THE CROODS

Grade: C-minus

Rated PG for scary scenes. Stars Nicholas Cage, Emma Stone, Ryan Reynolds, Catherine Keener, Cloris Leachman. Directed by Chris Sanders. Running time: 1 hour, 32 minutes.