Jack is eight and a half years old, and he is Annie’s older brother. He sees himself as the responsible sibling, trying to keep Annie out of trouble. He loves books and science, scrambling into the tree house once he learns that there are books inside, and uses the idea that he “could take notes like a scientist” to spur himself to meet dinosaurs (22). Through the course of the novel, he discovers that he can use his love of knowledge and reading to immerse himself in new settings and step outside of his comfort zone.

At the start of Dinosaurs Before Dark, he differentiates between himself and his sister by suggesting that he “liked real things” to her love of the imaginary (1). The tone of this comment foreshadows how the adventure will challenge Jack; time travel and dinosaurs are both impossible to him. Initially, he is hesitant about even leaving the treehouse, but both his brotherly concern for Annie and Annie’s insistence draw him out. To tackle his fear, his decision to take notes and examine the dinosaurs shows how he values knowledge and understands that while this trip is impossible in some ways, it is still an opportunity for him to learn.