The humor, largely centered around bodily functions and bathroom habits, is almost exclusively sophomoric.

While there is chemistry between the loud buffoon character, played by Jack Black, and Michael Cera as his meekly soft-spoken sidekick, this caveman saga/biblical retelling misses more often than it hits.

It starts promisingly enough. Zed (Black) is reviled by his tribe of zealous hunter/gatherers for his lack of skills. When he admits that he's not a good hunter, everyone — individually and collectively — always adds: "Or gatherer."

Oh (Cera) is brainier, but his hunting/gathering aptitude adds up to zero. Some of the movie's funniest moments take place as they struggle awkwardly to fit in within their primitive village.

The screenplay, which plucks random characters and modifies scenes from Bible stories, also seems to have drawn liberally from the Unabridged Encylopedia of Gross-Out Jokes.

Zed is prone to delusions of grandeur, early-man style. He defiantly eats from the tree of forbidden fruit. Convinced he has gained untold knowledge, he taunts Oh to test him.

"I might know everything," he proclaims. "Ask me something."

"Where does the sun go at night?" Oh asks.

"Pass. Next question," he responds.

And so it goes.

Upon fleeing their village, they meet Cain (David Cross) and Abel (Paul Rudd). Cain and Abel's father gives Zed his daughter to "lie with," while Oh must bunk with Cain and Abel's flatulent brother. You can see where this is going. And it's not a good place.

Later, they run into Abraham (Hank Azaria), just as he is about to sacrifice Isaac (Christopher Mintz-Plasse). While Azaria's circumcision gag is initially funny, it grows old.

They walk a few paces and end up in Sodom, which is where the comedy nearly comes to a standstill. Zed is convinced he has been chosen by God, while Oh is forced to spend hours massaging oil on a hirsute high priest (Oliver Platt). A few scenes feebly rip off Monty Python's Life of Brian.

While Cera is humorously low-key and Black has a few funny moments, Year One is scattershot and silly, squandering its potential by relying on juvenile bawdy humor.