How big did guinea-pigs use to be?

Guinea pigs, or cavies, are descendants of larger rodents that lived in South America. Their ancestors, such as the now-extinct Cavia porcellus, were notably larger, with some species reaching sizes comparable to a small dog. In contrast, modern domesticated guinea pigs typically weigh between 1.5 to 2.5 pounds and measure about 8 to 10 inches in length. This significant size reduction is attributed to domestication and selective breeding over thousands of years.