Bahun/Chettri stock represent the Aryans that came to the live in the fertile land of northwestern parts of India after leaving Central Asia where the climate was harsh and food scarce. After acclimatizing and cross-breeding with the local populace, they, too, started looking like the local inhabitants having darker complexion. Some Aryans moved westward into Europe and assimilated nicely there as well. That's why a whole language superfamily is called Indo-European which encompasses almost half of the languages spoken around the world today.