[rmlew]

You assume that Italy was empty in 1500 BCE for the Celt or Germans to come in.
Do a linguistic analysis. Heck compare paintings of Romans and descriptions to Germans.
Romans were short and Meditteranian looking. We are not talking Aryans here.

[weikel]

Julius Caesar was along with a lot of the aristocracy. You have to assume they were more ah inbred then the rest of the populace and thus less likely to have interbred over the years with southern Italians. Thus closer to what the original Romans generally looked like.