Fossil teeth from South America's oldest known rodents reveal that the creatures probably originated in Africa, roughly 40 million years ago.

Credit: R. SOC.

Because South America has a paucity of fossils older than 34 million years, the origins of the continent's rodents, including guinea pigs and chinchillas, have been debated. Pierre-Olivier Antoine at the University of Montpellier in France and his colleagues analysed the small, 41-million-year-old fossil teeth (pictured) from the Peruvian Amazon and found strong similarities with the teeth of the rodents' Old World relatives. These animals were probably among the first to adapt to South American habitats and it is likely that their last common ancestor came from Africa, which served as a stopover during the ancestors' dispersal from Asia.

Proc. R. Soc. B 10.1098/rspb.2011.1732 (2011)