YUNNAN

China’s most picturesque province, Yunnan. ... Historically, the town was a trading center between Tibet, Burma, and India. Mule caravans once made journeys
Peoples of YunnanYunnan is the most ethnically varied province in China. The following is an outdated yet interesting excerpt from Yün-nan, the Link between India and the Yangtze, by Major H.R. Davies, 1909, pp. 332-333. For up to date information regarding specific ethnicities, see the List of Chinese Ethnic Groups at English Wikipedia. An enthnic distribution map in Chinese can be found here (2MB).
The numerous non-Chinese tribes that the traveler encounters in western China, form perhaps one of the most interesting features of travel in that country. It is safe to assert that in hardly any other part of the world is there such a large variety of languages and dialects, as are to be heard in the country which lies between Assam and the eastern border of Yün-nan and in the Indo-Chinese countries to the south of this region.The reason of this is not hard to find. It lies in the physical characteristics of the country. It is the high mountain ranges and the deep swift-flowing rivers that have brought about the differences in customs and language, and the innumerable tribal distinctions, which are so perplexing to the enquirer into Indo-Chinese ethnology.A tribe has entered Yün-nan from their original Himalayan or Tibetan home, and after increasing in numbers have found the land they have settled on not equal to their wants. The natural result has been the emigration of part of the colony. The emigrants, having surmounted pathless mountains and crossed unbridged rivers on extemporized rafts, have found a new place to settle in, and have felt no inclination to undertake such a journey again to revisit their old home.Being without a written character in which to preserve their traditions, cut off from all civilizing influence of the outside world, and occupied merely in growing crops enough to support themselves, the recollection of their connection with their original ancestors has died out. It is not then surprising that they should now consider themselves a totally distinct race from the parent stock. Inter-tribal wars, and the practice of slave raiding so common among the wilder members of the Indo-Chinese family, have helped to still further widen the breach. In fact it may be considered remarkable that after being separated for hundreds, and perhaps in some case for thousands, of years, the languages of two distant tribes of the same family should bear to each other the marked general resemblance which is still to be found.The hilly nature of the country and the consequent lack of good means of communication have also naturally militated against the formation of any large kingdoms with effective control over the mountainous districts. Directly we get to a flat country with good roads and navigable rivers, we find the tribal distinctions disappear, and the whole of the inhabitants are welded into a homogeneous people under a settled government, speaking one language.Burmese as heard throughout the Irrawaddy valley is the same everywhere. A traveler from Rangoon to Bhamo (The Burmese capital to the Yunnan border) will find one language spoken throughout his journey, but an expedition of the same length in the hilly country to the east or to the west of the Irrawaddy valley would bring him into contact with twenty mutually unintelligible tongues.The same state of things applies to Siam (Thailand) and Tong-king (North Vietnam) - one nation speaking one language in the flat country and a Tower of Babel in the hills.