I'm not sure if this is the right forum to post this.
I'm thinking completely hypothetically and for a lark: but I wonder how Europe would have turned out if agriculture spread from Northeast to South rather than from Southeast to North (the Neolithic).
Imagine if agriculture was spread by prehistoric natives from the Baltic? Population patterns would have been reversed. Italians and Greeks would be the least genetically diverse. "Rome" as we know it would not exist, rather it would have existed in what is now Denmark, Sweden, or northern Germany.