So, I was recently reading about Everything Ernst Schafer and his scientific expeditions to Tibet. Himmler supposedly was a big supporter of his third and last expedition because he believed that the Aryan race originated in Tibet and that Schafer might be able to find some evidence of this. I know that Himmler had some pretty wild ideas, but this idea just seems pretty random. What led him to this belief?
I believe Himmler based this belief in the work of anthropologists during the 18th and 19th century. The discovery and translation of the Aryas, created this idea of an Indo-European people with a common ancestral language. The British actually used this 'Aryan' concept in their subjugation of India and the Maori people. Max Müller was a prominent German orientalist during the 19th century, and his works would have been easily accessible to Himmler. A little rambling of an answer, but its been awhile since I've looked at the subject.