It looks like mammalian brains may have another advantage besides size and structure. Armchair biologist that I am, I'm convinced the reason why dinosaurs won out after the Permian extinction was because of a metabolic efficiency our kind just didn't, and doesn't, have. After all, to this day one can easily predict the rough lifespan of a mammal just by its body mass, but when birds are judged by the same metric they live twice as long as they "should."

Did we end up on top because our brains are more efficient? It'd make for an interesting hypothesis to test!