History shaped the relation between Mesopotamia and Egypt, Asia and Africa. These two civilizations were the first to grow up around what we have come to call the 'Fertile Crescent.'
These two civilizations faced each other down because they saw only each other. For the Africans, there was nothing much of interest going on to the south and west; for the Asians, there was nothing much of interest going on to the north and east.
The great rivers truly fashioned the region. The rivers are important element in the biblical story because they serve as the origin of Man's independent power, the basis for his hubris; they are why man is able to believe his power rivals God's.
The Garden in Eden is the fulcrum of this geo-politics of rivers. In the biblical narrative, Eden is to be replaced by the Land of Israel, which decidedly lacks rivers but which focuses and unifies the geo-politics of region in a different way.