While browsing an out-of-print history book "Romans and Aliens" (no, not the kind from outer space) I came across an interesting comment made about the "Germans" (obviously the ancestors of modern day Germans as their were no Germans then): this author wrote that when any German would come south into the Roman Empire and take up a Roman lifestyle, their bodies quickly went "flabby."
The northern Europeans alive at the time of the Roman Empire were not a Paleolithic people as they did drink beer but surely they were not too far removed from the lifestyle of their Paleolithic ancestors. When they adopted a completely foreign Roman diet which consisted of agricultural products their bodies quickly reacted ... badly.
The ancient German was far taller than the ancient Roman but the Romans could outfight any German army. This author also noted that the Germans could not tolerate the sun and dust of the Mediterranean and would be often found lounging in the shade of the nearest tree. No wonder the Romans considered them complete wimps.
Make of this what you will.
