The Tocharians never ruled china, that doesn't count.
But keep in mind that the White race (in the broadest sense) extends over a very large area, 1/3rd of Asia and all of Europe and North Africa. Even kikes like Jared Diamond admit that. Most of those people would be called Aryans as well, root word from those who till soil, as they were primarily dependent on agriculture.
Of course, this region has become degraded, not so much shrinking as muddying. North Africa and the Arab lands have become much less suitable for agriculture than they once were, and the end of the ice age has encouraged the spread of more tropical traits, as well as the simple mass movement of people and insufficient in-group preference. Do keep in mind that not all White-aryans are equal. The Hajnal line, for example, demarcates clear difference between Europeans who have embraced forms of market based exchange and those who haven't. Furthermore, each region posses more local attitudes, the Germans are compulsive rule followers and the French are faggots who need to get sodomized with razor blade baguettes.