Climate also reflects on the level of available grass that the herders had to take into account when deciding where to move. Europe receives smaller quantities of precipitation as one goes from west to east, and then Europe's lush vegetation transitions into steppes and harsher climate beyond Volga region (Europe-Asia border). It must have been a tough call to decide to go eastward, and from what history tells us, that herders chose to migrate westward, not the other way around.