Baby or dog?

I imagine there are people out there who got a dog when what they wanted was a baby, but I wonder if there aren’t other people who had a baby when all they really needed was a dog. 

Ann Patchett, “This Dog’s Life,” in The Editors of The Bark, eds., Dog Is My Co-Pilot (New York: Three-Rivers Press, 2003), p. 24 (essay runs pp. 19-24). (Editors are Claudia Kawcynska and Cameron Woo.)