Do animals have a culture? What do we mean by "culture"? Lately social scientists have begun to ask if culture is found just in humans, or if some animals have a culture too. When we speak of culture, we mean a way of life a group of people have in common. Culture includes the beliefs and attitudes we learn. It is the patterns of behavior that help people to live together. It is also the patterns of behavior that make one group of people different from another group. Our culture lets us make up for having lost out strength, claws, long teeth, and other defenses. Instead we use tools, cooperate with one another, and communicate with language. But these aspects of human behavior, or "culture", can also be found in the lives of certain animals. Animals can make tools, for example. We used to think that the ability to use tools was the dividing line between human beings and other animals. Lately, however, we have found that this is not the case. Chimpanzees can not only use tools but actually make tools themselves. Animals can also share knowledge with each other and use their own language to communicate. So it may be important for us to know that the line dividing us from animals is not as clear as we used to think. The main idea of the passage is   _  .
chimpanzees can learn to use sign language to make sentences other animals can invent tools knowledge and communication are no longer signs of only human behavior the line dividing human culture from animal culture is not as clear as we might think