Changes

We first see evidence of the sail and sea-born ships depicted by the early Chalcolithic (6th millennium BC). The evidence comes from boat models and even tokens from sites in Arabia that were likely trade colonies or settlements established by a southern Mesopotamian (i.e., southern Iraq) culture, called the Ubaid culture, which was first established by 6500 BC and lasted until c. 4000 BC. <ref> For information about an early Ubaid period boat model from Kuwait, see: Carter, Robert. 2006. “Boat Remains and Maritime Trade in the Persian Gulf during the Sixth and Fifth Millennia BC.” ''Antiquity 80'' (307): 52–63. dos:10.1017/S0003598X0009325X.</ref> In the 6th and the 5th millennium BC, this culture began to expand and Arabia, particularly along the Persian Gulf coast, became a key focus region due to trade interests, including such items as copper and stones. The boat depictions from this era mostly suggest that reed boats with sails were utilized, where pitch, or bitumen, was used to seal boats to prevent them from sinking.<ref>Evidence for bitumen and barnacles on boats from the Ubaid are found from sites along the Persian Gulf, see: McCLURE, H. A., and N. Y. Al-Shaikh. 1993. “Paleogeography of an ’Ubaid Archaeological Site, Saudi Arabia.” ''Arabian Archaeology and Epigraphy 4'' (2): 107–25. dos:10.1111/j.1600-0471.1993.tb00045.x.</ref> In fact, impressed reed mats or evidence for them has been found along sites in the Persian Gulf. Most likely, prevailing wind patterns from the west in the Mediterranean and from the east in the Persian Gulf were well known and utilized by the early sailboats.

Up to this point, most likely ships had to stay near land in order to be near the shore to avoid storms, in essence they could shelter quickly if needed, and in order for boats to use land as a means of navigation. In other words, landforms served as markers to guide sailors. While the early sailboats were used to connect Mesopotamia and Iran with the Persian Gulf and the Levant and the Aegean world with the eastern Mediterranean, it took several more millennia before major new advancements were made.<ref>For more information about early Bronze Age navigating societies, see: Demand, Nancy H. 2011. ''The Mediterranean Context of Early Greek History''. Chichester, U.K. ; Malden, MA: Wiley-Blackwell.</ref> By the 2nd millennium BC, accumulated knowledge of stars and constellations began to facilitate more direct travel across the Mediterranean, particularly in the eastern Mediterranean, as trade began to expand, and other regions. As increasing knowledge of astronomy began to spread and became more precise, navigation across open water became more possible and less risky. Detailed knowledge of the constellations, eclipses, and moon movements made navigation during day and night much easier.<ref>For more information on how astronomy played a crucial role in improving navigation, see: Cotter, Charles H. 1968. ''A History of Nautical Astronomy''. London, Sydney [etc.]: Hollis & Carter.</ref>