Dogs have lived with people for a very long time. Scientists believe that humans and dogs have been friends for at least 15,000 years. This makes the dog the first animal that people ever kept as a pet. Today, there are more than 400 different breeds of dogs, from very small ones that can fit in a bag to very large ones that weigh more than an adult.
All modern dogs come from wolves. Long ago, some wolves began to come close to human camps to look for food. The friendliest ones stayed near the people, and slowly, over many generations, their bodies and behaviour changed. These new animals were no longer wild wolves. They were dogs.
Dogs help people in many ways. Some dogs work on farms, keeping sheep and cows together. Others work with the police to find missing people or illegal items. Special dogs are trained to guide blind people safely through busy streets. Of course, most dogs today are simply family pets, and they are loved for their company and loyalty.
Because dogs live closely with humans, they can understand many human signals. A dog can learn its name, follow simple commands and even guess what its owner is feeling.