Because obviously the chicken had to lay the egg.

It's basic science, but I'll start from the beginning for those of you who weren't blessed with a public school education like me:

God created the dinosaurs. Dinosaurs became extinct, for two different reasons. First let's take a look at the big dinos: Think of a brontosaurus. Those guys were huge. In fact, they were so huge that I'm guessing they didn't do a whole lot of copulating. Sure, they did sometimes... but not a lot. Eventually the Large Dino population dwindled and they became extinct. Now think of the smaller dinosaurs, like the little thing that killed Newman in Jurassic Park. This is the important part.

Ever hear of this thing called "evolution"? That's what happened to the little dinosaurs. First they were dinosaurs, and then over time they became reptiles, and then they became reptiles with wing-like arms, and then they grew feathers and suddenly they were birds. Then after they were birds they turned into chickens.

Once they were chickens, they started laying eggs.

Like I said, it's basic science. But I'm not expecting you to understand.