The tagline for the prehistoric adventure film “Alpha” — “Experience the incredible story of how mankind discovered man’s best friend” — is a bit of a spoiler.

Set 20,000 years ago in Europe, the story follows a young hunter named Keda as he fights to survive with the help of an unlikely ally: a gray wolf. But thanks to the spoiler, there’s never any doubt of our hero’s survival, or that of his lupine companion, despite an endless parade of near-death experiences that start out over-the-top but grow more tedious by the minute.

Aimed at family audiences despite a PG-13 rating “for some intense peril” (eyeroll), “Alpha” is director Albert Hughes’ first feature since 2010’s “The Book of Eli” (co-directed by his brother Allen). It delivers plenty of exciting action with some CGI-assisted visual flair, from stampeding bison to a starkly beautiful image of a frozen lake with our hero flailing on the wrong side of the ice.

Hughes’ efforts to bring emotional drama to the proceedings fall flat, however, relying on coming-of-age clichés that strip the story of any real surprise. Suspension of disbelief is also sorely tested by the weight of all that “intense peril,” along with countless tiny details that don’t stand up to scrutiny.

The plot is set in motion by the Great Hunt, an annual ritual in which the macho men of various hunter-gatherer bands team up to drive a herd of bison over a cliff. Keda (Kodi Smit-McPhee) is the son of the chief (Jóhannes Haukur Jóhannesson), but his sensitive nature makes it unlikely he will inherit his father’s leadership savvy. Even less so after a rampaging bison tosses him over the precipice.

While it’s true that fossils record this kind of mass kill in prehistoric times, it stretches credulity to believe hunters could have traveled hundreds of miles to do the deed (it’s a journey of some months, apparently, through mountains, forests and barren volcanic landscapes). But that’s just the beginning. There’s the scene of Keda, left for dead and suffering from a broken ankle, setting the bone by twisting his leg between a pair of rocks, splinting it with a stick and then … walking up a mountain?

Next he whips up a poultice using a stone mortar that looks to weigh about 10 pounds. Did all the hunters carry one through the wilderness, or just him? Maybe he made it out the same obsidian he apparently found lying around to make a spearhead out of it. We’ll never know, because dozens of such plot points are left unexplained.

There are plenty more examples, but enough spoilers. Suffice it to say that, if nothing else, “Alpha” is a paradise for nitpickers.

‘Alpha’

Studio 8 presents a film directed by Albert Hughes and written by Daniele Sebastian Wiedenhaupt. Rated PG-13 (for some intense peril). Running time: 96 minutes. Opens Friday at local theaters.