What Happened to the Dinosaurs

What Happened to the Dinosaurs

What happened to the dinosaurs?

Dinosaurs lived on Earth for 160 million years. Then, 65 million years ago, most of them disappeared. A few smaller ones slowly changed into the birds we have today. Other reptiles disappeared, too-flying reptiles and reptiles that lived in the sea. Many other kinds of animals also died out. And many kinds of plants.

No one knows why the dinosaurs disappeared. But there are many different ideas. Scientists look at the evidence and try to decide which idea is right. Maybe small animals ate dinosaur eggs so only a few eggs were able to hatch. This is one idea. But it does not explain why other kinds of animals died out, and many plants as well. Also, some dinosaurs may not have laid eggs.

Maybe a group of dinosaurs got sick and the sickness spread to other groups. That's possible, for even today diseases spread among herds of cattle. But if that happened, chances are the sickness would not have reached reptiles that lived in the sea. Also, other kinds of animals would not have caught the sickness, and neither would plants.

Some scientists have another idea. They study fossils in very old layers of rock and in newer layers, too. They think they see signs that every 26 to 30 million years, different kinds of animals and plants have died out. Maybe every 26 to 30 million years showers of comets hit Earth. These comet showers would change Earth so much that many living things would not survive.