Primeval is an average sci-fi series that keeps sucking me back in for reasons that I haven't completely figured out yet.
For the most part, the series is just a monster-of-the-week show. The characters are actually intelligent but the writers tend to ignore this fact in every episode for dramatic purposes. Or they use an even cheaper trick like having the clumsy geek trip over something. You will groan at least once each episode, trust me. Nitpickers should not watch this!
Despite all that, the basic premise of the series is interesting (although hardly original) and the background behind the anomalies is being developed, albeit very slowly. My instincts tell me that the writers have no idea where the anomalies come from but I keep watching just in case. Oh look, there's already a fourth and fifth series... ^_^