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38 Bolivia, which is now 13,000 ft. above the sea. But such an animal could not have existed at such an elevation. Then, again, in the deserts of Tarapaca, embedded in the sides of ravines, there are numerous skeletons of gigantic ant-eaters, animals whose habitat is in a dense forest. When they lived, the deserts in which their bones are found must have been covered with trees. It is the height of the Andes, wringing all moisture out of the trade wind, which makes Tarapaca a desert. When the Andes were lower, the trade wind could carry its moisture over them to the strip of coast land which is now an arid desert, producing arboreal vegetation and the means of supporting gigantic ant-eaters. When mastodons lived at Ulloma, and ant-eaters in Tarapaca, the Andes, slowly rising, were some two or three thousands of feet lower than they are now. Maize would then ripen in the basin of Lake Titicaca, and the site of the ruins of Tiahuanacu could support the necessary population. If the megalithic builders were living under these conditions, the problem is solved. If this is geologically impossible, the mystery remains unexplained.

We have indications of the megalithic civilisation, of the direction whence it came, of its great antiquity, of the extent of the ancient empire,