会有一些胶辅助制造。冰河时期只有步行吧

冰河時代走陸橋 因為大部分的海水被冰凍在兩極 海平面下降露出大陸棚

German Stone Age sailor to cross seas in reed boat可以看一下这篇报道。他们说埃及人的芦苇船可以跨国地中海一直开到黑海。 The choice of Varna as a port of departure points to the existence of the Varna culture dating back to 4,300 B.C., when it was an important Black Sea trading port. Greek islanders from Lemnos traveled to Varna, bringing valuable coral-colored spondylus (thorny oyster) shells which were spread around Europe and found in archaeological sites in various parts across the continent, including Germany.