Luc Seguin, age 13, of Ottawa, Ont., Canada, for his question:

WHAT REALLY BROUGHT AN END TO THE DINOSAURS?

This popular question must be tackled again and again because we have no proveable answer. Naturally, this challenges researchers to seek for more evidence. The latest theory on the departure of the dinosaurs is the most fascinating  because it suggests the possibility of a happying ending.

We have been told that the dinosaurs were scaly coldblooded reptiles that ruled the world for more than 100 million years and became extinct about 60 million years ago. A brand new theory, based on a wealth of believable evidence, is that many of those prehistoric animals were warmblooded and had hair or feathers.

One of the basic clues is the fact that warmblooded animals need far more food. After all, a lot of extra energy is needed to operate the biological thermostat that converts food into controlled body warmth. This calls for more elaborate blood factories within the bones. For example, the internal bone structure of a cat is far more complex than that of a lizard.

With this idea in mind, researchers took a new look at the old bones of the dinosaurs. And sure enough, many of them had the warmblooded structure that enabled them to convert food into body heat. Other evidence indicates that these had much bigger appetites than their coldblooded cousins.

There is fossil evidence that the ancestral birds which appeared during the dinosaur days had feathers instead of scales. It seems likely that other early warmblooded animals had hair.

This huge package of scholarly evidence indicates that the animals of the so called Age of Reptiles were far more varied than we had supposed. Some 300 million years ago, many types already had made the biological changes that appear in the following Age of Mammals. Perhaps it is time to reclassify the old timers in groups of ancestral types of birds, reptiles and mammals.

This new point of view wipes out the old idea that a world full of dinosaur populations suddenly became extinct. Perhaps they merely changed to keep up with the times.

The old theory of the dinosaur extinction seemed such a tragic story. It is nice to think that maybe this did not happen at all. Perhaps at least some of them changed through countless generations. And maybe some of their descendants gave rise to the remote ancestors of many of our modern animals.