Paul Landgraf, age 13, of Staten Island, New York, for his question:

Did the chicken or the egg come first?

Some folk think that there is no sensible answer to this trick question. But it so happens that there is. Let's start with a chicken, who came from an egg that came from another chicken. This egg and chicken route takes us back, way back through all the chicken ancestors that ever lived on the earth. If we keep going from egg to chicken to egg, we can trace the story back through several million years. And we still wouldn't know which came first.

Let's think about how things have changed through the long story of life on earth. At one time there were dinosaurs. And the dinosaurs took to laying eggs ages before there were any chickens in the world. In fact, scientists tell us that the dinosaurs were the ancient ancestors of chickens and other birds. If this is so, then we know for sure that eggs were invented a long, long time before there were any chickens in the world.