We have all been taught that evolution is the survival of the fittest. For example, there was this white moth whose population thrived. Through some mutations, some of these white moths gradually became darker, turning grey and black. Along came the Industrial Revolution. With the advent of factories, pollution increased. As the pollution increased, the darker grey and black moths became less visible to moth-eating predators. As a result, the darker moths eventually became the majority. (This is literally the only example of evolution I can remember from my schooling. For some reason, this has stuck with me for 20 some odd years.)
Now, we all know about the Tyrannosaurus Rex. They have big heads and little arms. This makes them less than ideal at, say, capturing a time traveling kid who is about to foil your diabolical plan. But, for this shortcoming, they evolved to excel in other ways. They were ferocious. And they were rather fast for their size. This made escaping the savage T. Rex especially difficult, even in your Jeep.
But at one point, there had to be at least one Tyrannosaurus who had proportionate, regular-sized arms. They could easily catch their prey. Pick things up. Carry things. Read books. Drive cars. Basically, lead a normal dinosaur life.
Somewhere along the line, of course, evolution stepped in. Evolution, who obviously has a sense of humor, decided that the little arms are best for survival. As a cruel joke on the king of dinosaurs, over the course of a few generations, heads got bigger as arms got shorter. This caused a divide across the top of the food chain. The “new, improved” T. Rex gained superiority. While the now odd-looking T. Rexes, those with usable arms, ran away, formed their own clan, and eventually died off.
But, before they left, you know there was that one T Rex with normal arms who looked around and was all, “Seriously? Come on, man!”