What are the advantages and disadvantages of keeping pets?请用英语回答这个问题。（100个单词左右）

Keeping Pets
Men have kept pets since ancient times. We can see from discoveries in the pyramids in Egypt and from scenes on decorated wallcoverings of European castles that our ancestors were as interested in pets as we are.
One reason for keeping pets is their utility. When our dog barks, it warns us of thieves. A cat keeps down the mice and rats in homes. When men depended on hunting for food they found hunting-dogs extremely useful. They also used a type of bird to aid them in their search for food.
Companionship is a non-utilitarian reason for keeping pets. If people are living by themselves they feel lonely, and having a pet relieves this loneliness to some extent. We like to have some companion with us even if this companion is not human. We feel the need to have another living being to share our daily lives. Having a companion, even if it is only an animal, gives us a feeling of warmth and an interest in something else beyond ourselves.
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