In many countries around the world fertility rates are dropping, and pets, particularly dogs, have begun to fill the void. That’s according to international relations professor Heidi Nast, who has been doing research for her forthcoming book, Petifilia. She says that since the 1990s, we’ve seen an explosion in the global pet market. People are now purchasing all kinds of goods and services for dogs, many of which were first developed for humans. Nast joins us to discuss the role of pets in modern life. (Photo: Flickr/winklerw)