The Knowledge Travels by Sea
The first urban settlements on earth were in Mesopotamia, where man was able to prosper because of the geography – farming made easy. The technology of the Mesopotamians was not a secret for long, and it moved south to Egypt and westward over the Mediterranean.
These are not movements of people in groups, they are the pathways of knowledge. Perhaps the craftsmen did move – the smiths and potters who were skilled enough to go with the highest bidder. Still, it was the absorbing of what was previously unknown that built the foundation of each successive society.
You see green arrows and white arrows, showing knowledge transfer by sea and by land. Funny thing about the land route, though. It stops at Troy. There is little evidence of knowledge crossing from Troy by land to the Greek Peninsula. Conversely, there is ample evidence for the sea route: to Crete, the Cyclades, and then Lerna in the Peloponnese.