The movie should have done better in theaters, and I want to acknowledge Hughes’s work in assembling this story with attention to some of the customs of people long ago. He obviously put in considerable research to maintain authenticity while still making it enjoyable. However, I believe the subtitles didn't help its performance at all, but instead contributed to the film’s sense of realism. Kodi Smit-McPhee, though, managed to hold the movie together while bearing a strong resemblance to Juliette Lewis, and sometimes even mimicking her movements. This proved somewhat distracting, particularly when the men and women needed to appear more rugged—much more so. Even with some problems with the computer-generated imagery, it remained an engaging film. It really pulled you in and felt like traveling back in time far more effectively than something like 10,000 BC ever could. Ultimately, the ability to take viewers back to early human life is what makes this film worthwhile, and Hughes achieved that much better than anyone might have expected from the director of "Dead Presidents." He has a clear talent for transporting audiences in that way.

Source on TMDB