Iris Damm, age 9, of San Diego, California, for her question:

Were there rattlesnakes in prehistoric times?

By history, we mean human history and this dates back some 6,000 years to the time when mankind learned to write down his historical events. Prehistoric times reaches back some four billion years to the birth of the earth. Mankind was a newcomer on the scene and. other animals had already been here for ages. It is true that our modern animals are very different from their ancestors. Generation by generation, all children differ from their parents. In time, the descendants may become unrecognizable and the remains of their long departed ancestors become lost in the past. But experts can trace back their family trees.

The family tree of our rattlers dates way back into prehistory. But their remote ancestors were not rattlesnakes, and farther back they were not even snakes. They were, however, reptiles, just as all the snakes are members of a large reptile clan. Experts tell us that about 100 million years ago, certain lizard type reptiles took to burrowing and gradually their descendants lost their legs. They became the 3,000 types of snakes in the modern world. The rattler and several others developed poisonous fangs at least 20 million years ago.