I don’t necessarily buy this interpretation but there is this book that implies are least a Bronze Age level of technology for said civilizations. Book is called “Maps of the Ancient Sea Kings”.
https://www.amazon.com/Maps-Ancient-Sea-Kings-Civilization/dp/0932813429/ref=sr_1_2?crid=36OI9E9I5I63S&keywords=maps+of+the+ancient+sea+kings&qid=1576513013&sprefix=Maps+of+the+Anc%2Caps%2C145&sr=8-2
Interesting..............