Rusty Wegner, age 11, of Youngstown, Ohio, for his question:
How did bears originate?
This calls for tracing back their family tree through countless generations of bear ancestors. For a long time they have been sizable animals with sturdy bones that the earth can preserve as fossils. What's more, the bears have been successful animals and quite plentiful in most of the world's cool and temperate zones. Hence, we would expect to find a fairly unbroken fossilized record of the bear family tree. And this is so.
The history of an animal family goes back through millions of years and, we hope, it will extend millions of years into the future. Almost always the changes are very gradual, with few noticeable changes through 1,000 generations or more. However, the bear family has changed a great deal through the past million years. We would hardly recognize the giant bears that shared the world of our cave man ancestors, just a few thousand years ago.
It would take years of your life merely to count the 50 million years back to the start of this animal story. Naturally, you would expect to find there a very different world from ours. Ancestral horses were no bigger than sheep. Fast trotting, pony ¬sized rhinos shared the meadows with camels like dainty gazelles. Elsewhere the ancestors of our great apes swung like monkeys among the trees.
Nature, even then, encouraged a few carnivores to weed out the failures and keep the herbivore populations within bounds. One meat eater of those far off days was a smallish furry mammal with short legs, a long body and a long tail, plus a pair of large perky ears. Scientists named him miacis. And my, what an ancestor miacis turned out to be. His descendants took about 30 million years to do it, but eventually they gave rise to the cats, the dogs and the bears.
Sometime in the dim past, miacis the original ancestor became extinct. But about 30 million years ago, one branch became dog types. Cynodictus was a slim, leggy creature whose descendants gave rise to the wolves and dogs. Daphaenus, called the bear dog, was as big as a coyote but much bulkier. He had a huge head, shortish legs and a very, very long tail.
About 10 million years ago, the survivors of the bear dog went through some startling changes. They grew huge and heavy and took to lumbering around on rather short feet.. Their teeth and skull bones also changed. Somehow their elegant tails dwindled to stubby buttons. At last the bear dog tribe gave rise to the direct ancestors of a wide assortment of bears.
During the past few thousand years, nature has cherished and fostered the human family above all her creatures.. Perhaps she is about ready to entrust her long, patient rule to us. Mankind, the intelligent one, can and probably must ordain the survival or doom of nature's world. It is up to us, for example, to decide the fate of the bears. After their long struggle to succeed, it would be a great pity if we allowed them to perish from the earth. So let's resolve to preserve these and all other endangered species from extinction.