From the considerations advanced in _Ethnology_, Chap. XII., it seems a reasonable assumption that the lacustrine Tibetan tableland with its Himalayan escarpments, all standing in pleistocene times at a considerably lower level than at present, was the cradle of the Mongol division of mankind. Here were found all the natural conditions favourable to the development of a new variety of the species moving from the tropics northwards--ample space such as all areas of marked specialisation seem to require; a different and cooler climate than that of the equatorial region, though, thanks to its then lower elevation, warmer than that of the bleak and now barely inhabitable Tibetan plateau; extensive plains, nowhere perhaps too densely wooded, intersected by ridges of moderate height, and diversified by a lacustrine system far more extensive than that revealed by the exploration of modern travellers[377]. Under these circumstances, which are not matter of mere speculation, but to be directly inferred from the observations of intelligent explorers and of trained Anglo-Indian surveyors, it would seem not only probable but inevitable that the pleistocene Indo-Malayan should become modified and improved in his new and more favourable Central Asiatic environment. Later, with the gradual upheaval of the land to a mean altitude of some 14,000 feet above sea-level, the climate deteriorated, and the present somewhat rude and rugged inhabitants of Tibet are to be regarded as the outcome of slow adaptation to their slowly changing surroundings since the occupation of the country by the Indo-Malayan pleistocene precursor. To this precursor Tibet was accessible either from India or from Indo-China, and although few of his implements have yet been reported from the plateau, it is certain that Tibet has passed through the Stone as well as the Metal Ages. In Bogle's time "thunder-stones" were still used for tonsuring the lamas, and even now stone cooking-pots are found amongst the shepherds of the uplands, although they are acquainted both with copper and iron. In India also and Indo-China palaeoliths of rude type occur at various points--Arcot, the Narbada gravels, Mirzapur[378], the Irawadi valley and the Shan territory--as if to indicate the routes followed by early man in his migrations from Indo-Malaysia northwards. Thus, where man is silent the stones speak, and so old are these links of past and present that amongst the Shans, as in ancient Greece, their origin being entirely forgotten, they are often mounted as jewellery and worn as charms against mishaps.