A competing theory posits their migration south, through the Rocky Mountains, ultimately reaching the American Southwest by the 14th century or perhaps earlier. An archaeological material culture assemblage identified in this mountainous zone as ancestral Apache has been referred to as the "Cerro Rojo complex". This theory does not preclude arrival via a plains route as well, perhaps concurrently, but to date the earliest evidence has been found in the mountainous Southwest. The Plains Apache have a significant Southern Plains cultural influence.