It seems likely from this information that neither the claim that Tibet has been completely politically independent of China over the past 2000 years, or the claim that Tibet has been inseperable from China since ancient times are 100% true.

Obviously China has played a role in influencing Tibet, but across the world there are examples of countries that have been influenced by their neighbors, but are still obviously their own nation.

It should also be mentioned that the same claims China uses to state that Tibet is a part of China should also mean that Mongolia should be a part of China. During the Manchu Dynasty, Mongolia was also recognized by China as a part of their empire.

In 1913 when Tibet declared their independence from China, Mongolia also declared their independence. Tibet and Mongolia signed agreements to recognize each others independence.

The Republic of China did not recognize the independence of either country. The only difference between them is that Mongolia became part of the Soviet Union's sphere of influence, which China could not oppose, so they finally recognized their independence in 1946.

Tibet and Mongolia have more in common religiously and culturally than either nation does with China.

Despite all of the evidence that exists, it is still possible for the historical status of Tibet to be disputed, if people really want to. But this should not get in the way on making progress on the status of Tibet at present. The people who are alive now are more important than anyone from the past, and it is these Tibetans who should be the focus of concern.