The main protagonist of "Jurassic Park" is Dr. Alan Grant. All in all Dr. Grant is a fairly static character. Yes, he is portrayed as the hero of the story, but he doesn't have the overarching hero transformation associated with characters like Spiderman. Dr. Grant starts off the story as a world renowned paleontologist. That sounds "nerdy," but Grant actively avoids being pigeonholed into that definition. He is an everyday common man who enjoys getting his hands dirty in field work. He's active and doesn't enjoy the cloistered world of dinosaur bone lab work. He's levelheaded throughout the story and is not easily biased or swayed in his opinions. He is in awe of the walking dinosaurs, but he is much more cautious about potential consequences than John Hammond would like. Dr. Grant acts caring and fatherly to both Tim and Lex right from the beginning, and that never changes.
All of the above characteristics stick with Dr. Grant throughout the story. It's one reason that I like Dr. Grant so much. He is exactly what he claims to be and acts exactly like you would expect him to act at all times. That may sound boring, but it makes him dependable.