The ganga river is the answer
The zambezi river is in Southern Africa.
We can not say that this areas are not civilized or to call them backwards. We may call them different. We can take for example the uses of animals in order to expand the commerce of their area. If we research about the use of camels, for example, we could see that it gained an special place within those who wanted to travel through many difficult areas like deserts. So in the case of camels they were not backwards, they used a different method to obtain success
