The lives of humans and animals have been intertwined since the beginning of civilization. Early humans learned to raise animals for food as well as to live alongside them as companions. Humans and animals develop strong interactions and lasting bonds to their mutual benefit. It is because of our close ties with animals that many people have mixed feelings about the use of animals in biomedical research—even scientists. In an ideal world, scientists would never need to use animals as research subjects. Because we do not live in an ideal world, some difficult ethical and moral questions arise
