A veterinarian told this story:

Yesterday a 10-year-old dog was brought to the clinic, who was ill with cancer and was dying. The owners decided to euthanize her because they didn't want her to suffer. The parents felt the need for their 6 year-old son who loved the dog to be present. When the dog was euthanized, the veterinarian was very surprised that the boy did not shed a single tear. Then she asked him if he knew why animals live much less than humans. The answer struck her to the core. The boy said: "Of course I know, people come into this world, to learn to love. And dogs already know how to immediately, so they do not need so much time..."