One strong piece of evidence pointing to the great length of time during which the Inca nations had been a settled and partially civilized race, is to be found in the plants that had been brought under cultivation, and in the animals that had been domesticated. Maize is unknown in a wild state,[1142] and many centuries must have elapsed before the Peruvians could have produced numerous cultivated varieties, and have brought the plant to such a high state of perfection. The peculiar edible roots, called _oca_ and _aracacha_, also exist only as cultivated plants. There is no wild variety of the _chirimoya_, and the Peruvian species of the cotton plant is known only under cultivation.[1143] The potato is found wild in Chile, and probably in Peru, as a very insignificant tuber. But the Peruvians, after cultivating it for centuries, increased its size and produced a great number of edible varieties.[1144] Another proof of the great antiquity of Peruvian civilization is to be found in the llama and alpaca, which are domesticated animals, with individuals varying in color: the one a beast of burden yielding coarse wool, and the other bearing a thick fleece of the softest silken fibres. Their prototypes are the wild huanaco and vicuña, of uniform color, and untameable. Many centuries must have elapsed before the wild creatures of the Andean solitudes, with the habits of chamois, could have been converted into the Peruvian sheep which cannot exist apart from men.[1145] [Illustration: LLAMAS. [One of the cuts which did service in the Antwerp edition of Cieza de Leon. Cf. Bollaert on the llama, alpaca, huanaco, and vicuña species in the _Sporting Review_, Feb., 1863; the cuts in Squier, pp. 246, 250; Dr. Van Tschudi, in the _Zeitschrift für Ethnologie_, 1885.—ED.]] These considerations point to so vast a period during which the existing race had dwelt in the Peruvian Andes, that any speculation respecting its origin would necessarily be futile in the present state of our knowledge.[1146] The weight of tradition indicates the south as the quarter whence the people came whose descendants built the edifices at Tiahuanacu. The most ancient remains of a primitive people in the Peruvian Andes consist of rude _cromlechs_, or burial-places, which are met with in various localities. Don Modesto Basadre has described some by the roadside, in the descent from Umabamba to Charasani, in Bolivia. These cromlechs are formed of four great slabs of slate, each slab being about five feet high, four or five in width, and more than an inch thick. The four slabs are perfectly shaped and worked so as to fit into each other at the corners. A fifth slab is placed over them, and over the whole a pyramid of clay and rough stones is piled. These cromlechs are the early memorials of a race which was succeeded by the people who constructed the cyclopean edifices of the Andean plateaux. [Illustration: DETAILS AT TIAHUANACU.