A computer animated film about a prehistoric family forced to look for a new home when their cave is destroyed doesn’t sound too promising, so had my friend Jerry Lapidus not recommended it, I would have missed this, and I’ve very glad I didn’t.
Nicolas Cage is the voice of Grug, a caveman who devotes himself to protecting his family with a combination of physical strength and a lot of rules -- curiosity is bad, anything new is bad, leave the cave only when necessary, and above all never not be afraid. His caution is well-founded. All the neighboring families have been wiped out by accident, predators, or disease.
Naturally, Grug’s teenage daughter Eep (Emma Stone) doesn’t like the rules. A bit of rule-breaking leads her to an encounter with Guy (Ryan Reynolds), a boy about her age who knows how to make fire and warns her of the end of the world, or at least of their part of it. Guy and the whole family are soon fleeing an advancing tectonic disaster.
The science here is shaky, and for that matter the weird fauna have little to do with real prehistoric life, but this is, after all, a cartoon. Grug’s mother-in-law (Cloris Leachman) even has a short, vaguely reptilian tail.
As one could predict geological ages in advance, Grug comes to resent his family’s growing dependence on Guy and the budding relationship between Guy and Eep, but the writing and acting (voice and animation) rise well above the obviousness of the basic plot. Even the predictable bits proved enjoyable.
That trailer doesn't get across the fact that the film is often pretty funny, so to illustrate that, here's one of the lesser comic bits: