Bruce Eveleigh, age 11, of Ottawa, 5, Ontario, Canada, for his question:
What was the earth like when the dinosaurs lived?
Mankind and his immediate ancestors has struggled through only a million years of patient progress. Meanwhile the world of nature around him has changed many times. The chapters have included four major ice ages, countless crustal upheavals and switches of scenery in the landscape. The story of the dinosaurs spanned 170 million years. During those long ages, the earth remodeled herself many times and each changing chapter created a different world.
Our luxurious world supports an estimated three million species of plants and animals. But a mere handful of them were there to share the earth with the dinosaurs and most of these were unrecognizable ancestors of our modern species. The Alps and the high Himalayas were still unborn, the geography of land and sea was very different and so was the earth's scenery.
The dinosaur story began with the Mesozoic Era, 230 million years ago, and ended when it closed, about 60 million years before the arrival of mankind. Small, early dinosaurs appeared in the Triassic Period of this era. They began to thrive when the warm; moist ages that had supported the swampy coal forests turned cool and dry. Other primitive reptiles and the few existing insects survived the climatic change. So did the mosses and lichens. But tough conifers replaced much of the old ferny foliage and the giant amphibians departed.
The Triassic landscape was a patchwork of wind blown deserts, scrubby slopes and soggy marshes. The little two legged and four legged dinosaurs grew bigger and more varied. Some fed on dry land plants, others on coarse water weeds and, as always, some dinosaurs dined on other dinosaurs. On our continent the east and west provided flurries of volcanic activity.
The following Jurassic Period remodeled our western scenery. The restless crust uplifted the mighty Sierra Nevada and a shallow sea swamped much of California. But the earth continued to favor the dinosaurs. They adopted a multitude of strange forms and stupendous sizes. A few took to the air and became the first birds. The dinosaur population explosion dominated all other creatures of the Triassic world.
Things were still favorable when the Cretaceous Period began. But this chapter of the earth's history brought mysterious changes that finally spelled the doom of the dinosaurs. The seas rose and swamped much of North America. Birds and insects multiplied and the primitive mammals improved. The plant world added many new species and at last the first green grasses carpeted the earth.
The dinosaurs thrived and survived through many changes of earth scenery. Then; their 170 million year success story ended. In just a few thousand years they declined and all of them departed. Perhaps they could not eat the new grasses or perhaps the mammals devoured their eggs. In any case, their stupendous population was wiped out and the earth's next chapter provided a suitable setting for the age of mammals.