Guinea pig
Guinea pigs (cavy) have perhaps been kept the longest as pets among rodents. While historically they served as a foodstuff for the native Inca people, they were imported to Europe as early as the mid-16th century, shortly after Spain conquered Peru. As an oddity from the New World, they were afforded a special status, and seen as house pets, rather than vermin or food. While their popularity was initially limited to the wealthy, their prodigious reproductive habits ensured that they spread throughout the middle classes shortly after their introduction; guinea pig burial places (not scattered bones—as would be found with an eaten animal) have been found in archaeological digs in early modern middle-class suburbs.