Natural History

The Guinea pig is a popular first pet for many children, but the identity of its wild ancestor remains unclear.

The familiar Guinea pig has long been a first choice for parents seeking a first pet for their children. The species is known for is rather placid temperament and relative ease in its husbandry.  It comes in several different coat types, which vary from the long-haired Peruvian to rough-haired Abyssinian to the completely hairless Baldwin, and a wide array of colors, including tortoiseshell and brindle varieties.

However, unlike most domestic animals, we are still unsure of the Guinea pig’s ancestor.  We have several candidates, but it is possible that the domestic Guinea pig’s ancestor is an unknown species.  So let’s explore the candidates.

First of all, in case you didn’t know, Guinea pigs have a totally false name. They are not from any country known today or historically as Guinea, including the island of New Guinea. They also are not swine. They are hystricomorph rodents, and the Guinea pigs and the various South American relatives, including the capybaras, pacas, agoutis, and maras, are considered in infraorder Caviomorpha. The cavies make up a specific group  in the Caviomorpha infraorder, and these things vary greatly in appearance. The most famous of these is the Guinea pig, but the capybara is also pretty well known. The capybara is a giant cavy that lives a semi-aquatic lifestyle. My personal favorite of the cavies of is the mara, which looks like a cross between a Guinea pig, a hare, and an antelope. However, also included in this cavy group are several nondescript rodents that could be the ancestor of the domestic Guinea pig.

The Brazilian cavy (Cavia aperea) is sometimes considered the Guinea pig’s ancestor. It can produce fertile offspring if hybridized with the domestic Guina pig, but after several generations, fertility becomes an issue. Because fertility does not continue through the generations, it is likely the the Brazilian cavy is just a very close relative of the Guinea pig and not its immediate ancestor.

The Shiny Guinea pig (Cavia fulgida) might be an ancestor, but it leaves in Eastern Brazil, which is quite far from where we know that the Guinea pig originated, which is the highlands of Ecuador and Peru.

The Montane Guinea pig or the Tschudi’s cavy (Cavia tschudii) seems to be a more likely ancestor. It is native to the same regions where we know the domestic Guinea pig originated. However, studies of the biochemistry of this cavy and the domestic Guinea pig suggest that they are not the same species. Thus, Tschudi’s cavy is probably not species we are looking for.

Things do get somewhat confusing because in some parts of Peru, Ecuador, and Bolivia, Guinea pigs are very common as domestic animals. Feral populations of these animals can be found, and it can be difficult to determine whether one is looking at a true wild cavy of a different species or an unsusually pigmented feral Guinea pig. For example, one of the first specimens of Tschudi’s cavy that was sent to Europe appeared to be an agouti pigmented domestic Guinea pig. Further, there is a documented cavy near Bogotá, Colombia, called Cavia anolaimae. It is said to be very similar to the domestic Guinea pig, but it often considered to be nothing more than a feral Guinea pig. Another unusual Guinea pig (Cavia guianae) has been documented in northern Brazil, southern Venezuela, and Guyana. It is not clear whether this is also a feral population of domestic Guinea pig, a population of Brazilian cavy, or a new species, which could be the Guinea pig’s ancestor.

However, it is possible that these anomalous cavies are actual the ancestral Guinea pigs. Perhaps through regular hybridization with domestic Guinea pigs that the wild populations of these animals became severely reduced. After all, the parts of South America where the Guinea pig was first domesticated have gone through great upheavals through conquest, civil wars, and other strife. As a result, it is likely that domestic Guinea pigs, where were kept so closely to their villages as a food source escaped into the wild. There, they hybridized with the wild ancestral Guinea pig, whatever it is or was, and then polluted its gene pool until it disappeared through hybridization. This theory is the one I think more likely, but it’s just as possible that the unsual Guinea pig-like rodent sent back with the first Tschudi’s cavy was one of these wild Guinea pigs. It’s also possible that the unsual cavies that are called  Cavia guianae and Cavia anolaimae are relict populations of this wild cavy that is the ancestor of the domestic Guinea pig.

It is hard to believe that we know very little about the domestic Guinea pig’s ancestry. We know what its closest relatives are, but so far, none of them are thought to be their direct wild ancestor. Maybe someone will do an in depth analysis of Guinea pig and wild cavy molecular evolution, which will lead us to the answer. Right now, all we can do is speculate.