“Alpha” has to stand as one of the pleasant surprises of the cinematic summer, a gritty yet sentimental fantasy about that first Ice Age boy to fall for a dog.

It’s a movie with more blood and guts than Disney would have allowed. But any movie with a teen and a dog in it is going to tug at the heart, even if the dog’s a wolf and the kid’s not much further along the civilized scale. And while it’s not on a par with that classic of pre-history, “Quest for Fire,” director Albert Hughes (“The Book of Eli”) gives us a beautifully barren prehistoric Europe of steppes, volcanoes, mesas and canyons, a forbidding land presented in magnificent 3D.

Keda, played by Kodi Smit-McPhee of “The Road” and “Slow West,” is the son of the chief (Jóhannes Haukur Jóhannesson) of his tribe of hunter-gatherers, good with his hands (he fashions enviable flint spearpoints) but sensitive, a bit of a mama’s boy.

He may pass spearhead making, but he flunks his first and second Big Tests on the joint tribal hunt, refusing to finish off a wounded wild boar that squeals in pain and looks him in the eye, terrified. That second test, fleeing the bison the hunting party are chasing off a cliff, gets him gored and flung down a cliff-face.

Mother (Natassia Malthe) will have only his memory to cling to.

But Keda, left for dead, clings to that cliff, re-sets his busted ankle and using the tribal tattoo — a constellation inked on his hand — he might be able to find his way home. If only he can dodge the saber tooth tigers, hyenas and wolves.

It’s one of those that almost gets him, and one of those that he almost kills defending himself. Showing empathy, he nurses himself back to health and tends to the wary wolf he knifed as he does.

The production almost seamlessly marries CGI wolves to a real wolf for some scenes, mostly close-ups. Hughes may give us windswept vistas and time-lapse scans of the night sky, but “Alpha” lives or dies on its extreme close-ups — hunters, camouflaged in mud, crawling up on the herd, a wolf softening its fear of fire and the humans who create it (with great difficulty).

The kid talks to the wolf — in a subtitled pre-Greek or Latin dialect — far too much for my taste. The movie itself is chatty when in essence language was a newish thing and vocabularies were limited enough that using gestures and images to tell the story would have been a safer, smarter and more cinematic bet.

Still, there’s value in a father teaching his son, “Raise your head, your eyes will follow” and that wolfpacks are led by the Alpha dog, not an inherited title, “but one won through courage.”

Hughes, who came up with the story the script was based on, has fashioned the simplest of quest narratives and rarely gets in the way of it. He takes us exactly where we expect him to.

But he gets the boy and us to connect with the dog and has a little fun showing us boy-and-his-dog firsts — first whistle to call Alpha (what he’s named the dog), first accidental game of fetch.

It’s kid-film cute some of the time, pretty rough and bloody going at others. But “Alpha” holds together well-enough and exceeds expectations. When this was first announced, I was sure Sony would animate it, “Ice Age” style. I’ll bet you were, too.

Smit-McPhee is no Leo and “Alpha” is no “Revenent.” But in an era where films have shied away from challenging, scaring or hitting kids with anything resembling harsh reality in critter features, “Alpha” is a lovely yet tough-minded reminder that the cuddly Spaniel or Pomeranian curled up at your feet didn’t get there by accident, or by being a pushover.

Then again, maybe that’s exactly what put him there.

MPAA Rating: PG-13 for some intense peril

Cast: Kodi Smit-McPhee, Natassia Malthe, Jóhannes Haukur Jóhannesson, Leonor Varela

Credits:Directed by Albert Hughes, script by Daniele Sebastian Wiedenhaupt . A Sony/Columbia release.,

Running time: 1:36