Historians are not sure when humans first started keeping animals as pets. Keeping an animal for pleasure rather than for food or work was possible only for people who were well off and had the resources to feed extra mouths. Dogs most likely were the first pets, because they were domesticated so long ago. The ancient Romans are known to have kept pets, particularly dogs and birds. Cats and horses were also popular with Romans and may have been considered pets, but they were also working animals. The origins of ornamental goldfish date back to the seventh century in China, where Buddhist monks first raised them in ponds. By the fourteenth century the Chinese were keeping goldfish indoors in bowls as pets.
During the Middle Ages many pet cats were put to death with their owners on suspicion of witchcraft. It was during this period that dog breeding became popular in Europe. Although many dogs were bred for herding, guarding, and hunting traits, some breeds were tailored to pet owners who desired certain coat characteristics, sizes, and behaviors. Pet ownership was mostly limited to the upper classes of society—royalty, aristocrats, and landowners.
The first American colonists brought a few pets with them to the New World, but life was hard in the colonies, and resources were scarce. Few people had extra food to give to an animal unless it was being fattened up for slaughter or earning its keep by working. Some dogs and cats may have been called pets, but they also performed useful tasks such as guard duty and killing rats. The modern age of pet keeping began in the mid-1800s, when a thriving middle class emerged in society. This was the first time that many people had the time and money to keep animals solely for companionship and pleasure.
According to historian Kasey Grier of the University of South Carolina, tropical birds, such as parrots, were highly valued in American society before recorded music became available. They were the first animal companions for which goods were specifically marketed, including
bird food, medicines, cages, and other accessories. The Pet Food Institute reports that the first commercially prepared dog food was introduced in England around 1860. The first goldfish were bred in the United States in 1878. Canned dog food was introduced in the United States following World War I (1914–18). Dogs, tropical birds, and ornamental fish were the house pets of choice well into the twentieth century. The keeping of horses for personal enjoyment rather than for work also grew. In 1947 cat litter was introduced to U.S. consumers, making it much easier to keep cats indoors. They too became prized as pets and eventually surpassed dogs in popularity.
Some unusual pets have interesting histories. Guinea pigs (or cavies) are rodents that originated in South America. It is believed that during the 1500s Spanish explorers introduced them to Europe, where they became popular house pets. Queen Elizabeth I (1533–1603) of Britain is said to have kept a guinea pig as a pet.
The first recorded instances of people keeping rats for pets are traced to nineteenth-century London. Professional rat catchers earned a living by ridding the city of rodents. A rat catcher named Jack Black was among the first to take in and breed rats with unusual colorings and fur for collectors. Another man named Jimmy Shaw ran a rat pit, or a sporting house in which dogs competed to see who could kill the most rats. Legend has it that Shaw kept and bred rats with unique colorings and sold them as pets.
Gerbils are rodents that were originally found in Mongolia during the 1800s by French missionaries. The animals were used in laboratory research beginning in the 1950s and became popular as pets during the 1970s. Hamsters are rodents native to Syria and other Middle East countries. They were brought to the United States in the 1930s as laboratory research animals and eventually became popular as pets.
The ferret craze began in the 1970s. Ferrets are descendents of European polecats and members of the weasel family. There is some disagreement among scientists and politicians about whether ferrets are completely domesticated or not. They have been banned as pets in California, Hawaii, and some municipalities (including New York City). In California ferrets are classified as "detrimental animals" and are believed to pose a threat to native wildlife. In New York City ferrets are considered a threat to public health and safety.