How do we know about cavemen?

  People who lived thousands of years ago were untidy. They left garbage, broken tools, and all kinds of trash wherever they camped. When they finished gnawing on a bone, they just tossed it away. Those who lived in caves dropped a great deal of stuff on the floor. They also left ashes from their fires.
  Scientists have dug into the floors of some caves and have found layer after layer of trash and ashes. Only human beings could have created this mess. Bears and other animals don't build fires or make arrowheads, chipping off little flakes of flint. Bears don't drop beads and broken pottery around.
  By studying the trash heaps, a scientist can learn a great deal about what the cavemen ate, the clothes they wore, the tools and weapons they used. It is even possible to examine a skeleton buried in the trash and then figure out what cavemen looked like.
  In a few European caves ancient artists painted beautiful pictures on rock walls far underground. They used twigs or bits of moss for brushes. They mixed colored clay and vege­table dyes into meat grease for their paints. With only smoky torches for light, these first artists drew wonderful hunting scenes and painted the portraits of animals that have now disappeared from the earth. Only one or two of the pictures show people, but they tell us a great deal about the cavemen just the same. These were not stupid creatures who went around hitting each other on the head with clubs. Instead, they were clever inventors and talented artists. They had a sense of humor, too, for they even drew a few cartoons.