As humanity has got richer, animal's roles have changed. People need their services less than before. Fewer wolves and thieves meant less demand for dogs for protection; the internal combustion engine (内燃机) made horses unneeded; modern sanitation (卫生设备) kept rats in check and made cats less useful. Domestic animals are no longer necessities, but commonly seen companions. Pet-keeping seems to become more and more popular, as a recent survey found that 69% of American households keep at least one pet.

The pet business is growing even faster than pet numbers, because people are spending more and more money on them. No longer are they food-waste-recyclers, fed with the remains that fall from their masters' tables. Pet food shelves are full of cuisines tailored to satisfy a range of appetites, including ice cream for dogs and foods for pets that are old, diabetic, or suffer from sensitive digestion.

In the business, this is called "pet humanization" — the tendency of pet owners to treat their pets as part of the family. This is obvious in the names given to dogs, which have evolved from Fido, Rex, and Spot to Bella, Lucy, and Max.

People still hold the false assumption that pets must be working for humanity in some way, perhaps making people healthier or less anxious. But the evidence for that is weak. New research suggests that dogs have evolved those "cute eyes" to affect human emotions and control them, which works very well. Humans now work very hard to pay for the care of their pets. For example, Americans often refer to themselves not as cat owners but as the cat's "mommy" or "daddy". South Koreans go one step further, describing themselves as cat "butlers (管家)". Watch an unlucky man walking his dog, plastic bag in hand to pick up its mess, and we have to doubt: who's in charge now? Is this relationship what we really want?