I was wondering for some time how was it possible to appear this belief that the typical Aryans have to be blue-eyed blond people, transformed later into a theory heavily supported by Nazis. These physical features appeared among proto-European populations, after living for thousands of years in Northern Europe. The Indo-European immigration in that area is fairly new at that time scale. And it's not very sure if it was a real immigration or a linguistic diffusion.

The German language itself has enough features that point to an substrate (by a theory, Fino-Ugric) from a previous population:
http://en.wikipedia.org/wiki/Germanic_substrate_hypothesis