Summary: During the last millennia, the sea level all around the world was subjected to many fluctuations, causing some desorder in the course of the human civilizations. Floods occurred and land connections were broken. In the Gibraltar area, the link between Iberia and today Morocco is thought to have been definitely lost for 15.000 years, as the end of the Ice Age caused great quantities of snow and ice to melt and run into the Atlantic ocean.

Yet, the zoogeographical datae support the idea of a more recent up-and-down transit of animals in this area, reflecting the situation when the European and African continents were joined, until an obstacle like the Strait of Gibraltar limited the dispersal capacities of the organisms.

In the context of human settlements, the presence of a protohistoric landbridge allows us to emphasize that many events have occurred in a way that is not consonant with the usually recognized theses.

The author of the present paper thinks of the possibility that prehistoric civilizations were in possession of boats capable to reach distant places. In fact, Pleistocene mariners could have crossed the Atlantic and got into trade on both sides of the ocean. Cro Magnon originated from Central America, and transoceanic contacts between Europe, Africa and the Americas, were rather regular during the Upper Palaeolithic. This will be discussed.

In recent periods (Neolithic, Chalcolithic), transoceanic voyages continued to be undertaken, from each side of the Atlantic. At some regards, a great circum-atlantic civilization (Megalithics) can be postulated. Later, as the Strait of Gibraltar became definitively open, the Phoenicians, as the heritors of the Megalithics, went on to cross the Atlantic for commercial purposes; they were the guardians of the "Pillars of Hercules", and let other people think there was nothing to find in a westerly direction...